LT1/0411 PCM/Opti Delete

[sandrock]

I've threadjacked a few threads asking questions that happened to be relevent to the post, but I thought I would post a brand new thread to try to mush all the info together and *hopefully* come up with system that doesn't involve spending bukoos of cash through EFI Connections (Not knocking them at all, but the cost of what you get seems like it's mostly paying for R&D).

First, I'll lay out the parts n' stuff....let's take an LT1 w/96-97 timing cover (for crank sensor), the 0411 computer, an LS1 cam sensor (or equivalent...the type that goes in a timing cover), and a fully disassembled Optispark, minus the Opti since it won't be needed at all.

Now, let's lay out some parts that have yet to be made...a blank Opti distributor cap, a new cam sensor reluctor (based on the original optidisk, instead of all the holes the original has, this one has a full 180* cut out of it, with about 1/8th of an inch left around the perimeter).

There are still more parts that need to surface, but those have yet to evolve (crank sensing stuff basically). The short of it is taking any year Opti distributor and refitting it with LSx cam sensing technology. I had thought about throwing in some Vortec parts, but those parts seemed a bit bulky for what I wanted to accomplish. The cam sensor will either a) mount on the blank opti cap, with the height of the cap determined by the length of the sensor chosen, OR find a flush mount sensor (like the Opti sensor, but not using optical pickup) and mount it to the Opti base where the original sensor was. This would be ideal, since this would allow continued use of the distributor (The 4x crank/1x cam can be run by the 0411 with the Vortec 5700 OS from the Express Van), further reducing costs.

Depending on how the new shutter wheel is cut, it could also work with the N*DIS as well. Going that route, a new crank reluctor would have to be cut. To take care of the needed 2nd crank signal, I am wondering if it is possible to send the one crank signal to a circuit card that will 1) Pass an unaltered signal through it to act as signal 1, and 2) Pass the same signal but retarded 27*(?) at all times to act as signal 2. In theory, that would work.

Anyone else have any thoughts on this??

[EagleMark]

Slight hijacking is fine to learn enough to start your own thread. :happy: We encourage conversation and learning.

EFI Connection (http://www.eficonnection.com/eficonnection/24x.aspx) has done this but I like you, would rather do my own, let alone cost.

I think machining a cam reluctor for Opti like dave w does, then machine a cap to elimanate cap and orotor would be cost effective and look good when done. Since I have an Lt1, when it needs an Opti I could probably do this cheaper than cost of Opti.

Here's some good info from EFI Connection on the swap in PDF below.

[JeepsAndGuns]

If your talking about using the northstar dis system, then I am guessing you want rid of the distributor. So why not just install the 24x crank trigger wheel and run the coil per plug ignition the 411 pcm can run.
You chevy guys have it easy when it comes to running the 411 pcm.

[dave w]

I like the idea of using custom designed externally mounted (on or around the harmonic balancer) Crank / Cam reluctors and sensors. Might take me a few hours in CAD to get something designed. Seems to me the only low cost way to convert the 96 / 97 LT1 to an '0411 is the externally mount the '0411 OEM parts. I did something similar with the 4x '0411 crank position sensor and reluctor. I can get things made with either Wire EDM or a CNC machine.

dave w

[EagleMark]

If your talking about using the northstar dis system, then I am guessing you want rid of the distributor. So why not just install the 24x crank trigger wheel and run the coil per plug ignition the 411 pcm can run.
You chevy guys have it easy when it comes to running the 411 pcm.Don't think there is a 24 tooth relector wheel available? Maybe aftermarket like EFI connection. The 24x crank sensor is an available GM part. The 96-97 LT1 have 4 tooth reluctor wheel for crank trigger. The 94-95 LT1 do not use crank trigger but can bolt on 96-97 timing cover with crank trigger sensor, for that matter I think it bolts to all SB chevy engines.

[sandrock]

If your talking about using the northstar dis system, then I am guessing you want rid of the distributor. So why not just install the 24x crank trigger wheel and run the coil per plug ignition the 411 pcm can run.
You chevy guys have it easy when it comes to running the 411 pcm.

I like to keep options open. Obviously keeping the dizzy portion of the Opti operational would significantly lower costs for anyone wanting to upgrade an LT1 to the 0411. DIS would be the next cheapest as you can find those coils in damn near any junkyard. Coil near plug would be the high end of the scale, but would require the 24x reluctor (which only exists aftermarket and at a very high cost...somewhere around 200 bucks). For the sake of getting my build operational, I'm going to concentrate my efforts on keeping the Opti dizzy operational.

I've done some research last night and from the looks of things, the three OEM sources for the type of cam sensing and packaging I need are GM (Vortec sensor and custom reluctor), Mitsubishi, and Hyundai. The sensors are Hall-effect, and look like they take a disk as a reluctor....exactly what is needed. I left my list at the house, but I had picked about 6 of them out. So long as they send the required signal out, the PCM won't care where they came from.

[EagleMark]

The Opti already has a Mitsubishi optical sensor and the reluctor ring is a thin disc, I wonder if you could just use what's there? I'll attach a pdf for the Opti information.

Keeping the Opti distributor and running coil on cylinder has already been done.
http://www.lingenfelter.com/mm5/merchant.mvc?Screen=PROD&Store_Code=LPE&Product_Code=BAI-LTCC&Category_Code=C51

More than you'll ever need to know about the Opti Distributor from GM!

http://www.youtube.com/watch?v=lFCjaz6zHfc

[sandrock]

I can't use an Opti sensor or trigger wheel as they are....the 0411 won't play well with it at all. The Mitsubishi sensors I've been spying on ebay were meant for their 2.0 liter engines, and a few 3.0 engines, with Hall-effect cam sensing. Here's a pic of a Hyundai sensor...same as a Mits, just different connector.

http://i81.photobucket.com/albums/j219/starion_esi/1996%20Camaro%20convertible/hyundaisensor.jpg

It looks similar to the Opti sensor, hopefully it will mount the same or close to it.

Here's the Vortec sensor...
http://i81.photobucket.com/albums/j219/starion_esi/1996%20Camaro%20convertible/vortecsensor.jpg

And a Ford reluctor
http://i81.photobucket.com/albums/j219/starion_esi/1996%20Camaro%20convertible/reluctor.jpg

Just modify that Ford reluctor to spit out one signal.

[EagleMark]

So the Opti sensor is wrong signal? Even if it had the correct reluctor?

I have an Opti here taken apart and was trying to find a replacement bearing to rebuild it. The sensor and trigger wheel (relector) are very reliable. Problems are moistre, venting and Oring seals are when they have problems with all the high voltage spark from coil to spark plug wires. If high voltage spark was gone it would be foolproof. Actually it is foolproof for over 100k miles. Some guys have over 200k on them with new cap-rotor and seals. I found the moisture/ air leak in origanal design is the bearing to housing! If it were sealed then it would be vacuum tight and the vent system would be 100%, now it's not!

[sandrock]

I sent an email to EFI Connections and asked if they had explored the option of just changing out the Opti wheel to spit out the corrected signal. They responded back saying the signal coming out of one they tried that on was garbage. And in every instance I've seen where an Opti distributor is used and the LT1 PCM isn't, there's always been some sort of translator box in between the two.

The biggest issue with doing away with the dizzy and going coil near plug is the crank reluctor. For the LT1 and the Vortec 350, the rear of the block has one, maybe two, areas near the bellhousing that look like they may be places for crank sensors that got lost in evolution. If that's the case, bolting on a reluctor to the front of the flywheel could be a very easy way to get that signal (IF the engine is already out). EFI xn did their design to be easliy fitted into the engine w/o taking it out, but...this could work too.

[EagleMark]

Well that's one option and a good one if you had the engine out. I would get it done and ready even if I didn't use it at first!

But I can't see doing that in a good running car? So the options left are 96-97 timing chain cover that has the place for crank sensor and four tooth reluctor wheel and readily available parts from GM. But still have to get a keyway from GM and machine down crank hub to fit, or buy 96-97 crank hub? then single row timing chain cause double won't fit. If you've gone that deep you may as well make the cam sensor reluctor just like theirs and do away with the distributor completly. Or make a cam reluctor and cam signal sensor into Opti... seems like a step backwards since your already in there, gonna cost the same to make parts on cam as it is in Opti.

So cost wise if you need an Optispark distributor that's $400. plus labor to have best available ignition system of it's time. Good for another 100K miles. Tuner equiptment cheap and I already own OBDI

Don't think you could do cam cover, timing chain, reluctor, crank sensor, cam sensor and cam reluctor for $400? then still have to add 8 coils and plug wires, then wiring. then how much work to install an LS1 PCM? and cost? then need way expensive OBDII tuner equiptment. I see this turing into a $2000. upgrade at the low end!

Just priced the 24x system from EFI connection at $2120... still no tuner equiptment so $3100?

So for a $2000 upgrade I could do a new opti wires plugs headers exhaust cai roller rockers and probably a cam.....

For $2000 I can get a complete LS engine trans with harness and PCM from Spaldings in Spokane and install it in a car. Few years from now you could probably buy an LS engine car or truck for $2-3000

I was thinking of doing something like this, this winter because I have a waterpump or opti seal leaking, but I'm just going to service as neccessery and enjoy what I got.

Now what does the Moates RoadRunner require to run coil on plug? I know it will tune real time for LS1 engines but also heard it will run LT1? I've been wanting to buy a RoadRunner so I can buy TunerCat OBDII software license. It's the only way to get it since the rights were sold to Jet under the Dynamic Spectrum Tuner name. With Jet your at $100 license per vehicle. Tuner cat is no limit per VDF file. RoadRunner and Tunercat with all definitions and cables would be $2400. and I could tune OBDII cars forever without another penny for licenses...

[sandrock]

Some of it I already had.

Tuner - HP Tuners suite. Bought this for a previous project, made a few bucks with it. However, I feel that will change the more F-body owners in OKC know I have it. This was an ebay buy around 250, and it still had 4 credits left.

PCM - 25 bucks off of ebay. Bought for a Suburban project that went south.

Various connectors from harnesses I've collected through the years.

As much as I'd like to do coil on plug, the most cost effective option in this case would be to convert the opti to Hall effect and run it, with the second to convert the intake manifold to run a Vortec dizzy. And true, I wouldn't be doing any of this if I got a full running car in the first place. Instead I got a shell and I'm pieceing everything together bit by bit (My garage is like the ending scene from "The Iron Giant" where all of his pieces are slowly making their way across the world to his crash site so he can put himself back together)

So my costs for this are....
HP Tuner credit 100
Vortec Diz 50 (I actually had that beforehand, but I'll still include)
Timing cover 75 (with reluctor)
Manifold mod 250 (Obviously most expensive, but done right. Mount needs to be 1/4" above the surface, and egr will
probably need to be milled out. Not a big issue, I'll run linear EGR in its place)

Doing it that way, the cost isn't much more than a new Opti system, plus you relocate the dizzy in a much safer, though less convenient, place. HOWEVER, I'm still going to persue the 24x bellhouse reluctor idea, just because the engine is out and apart. It makes sense to do that now, so that way, like you said, it's there when I am ready to go COP.

[JeepsAndGuns]

Hopefully its not too off topic from this thread. But I have a question I have been wondering about for a good while now.
WHY is the tuning software for the 411 so dang expensive!?!? And whats the deal with this vin licencing/credits/etc.. that you have to have before you can even read and tune a pcm. Then, if you want to tune another pcm, you have to buy more.
I understand the people that made the software want to get paid for their efforts, and I think they should, but dang, it just seems a little excessiave. $500 is a far cry from $40 for tunerpro. And the thing where you have to continue to pay if you want to tune more pcm's just seems like highway robbery. Heck, the 411 is coming up on being almost 12 years old now.

[dave w]

Hopefully its not too off topic from this thread. But I have a question I have been wondering about for a good while now.
WHY is the tuning software for the 411 so dang expensive!?!? And whats the deal with this vin licencing/credits/etc.. that you have to have before you can even read and tune a pcm. Then, if you want to tune another pcm, you have to buy more.
I understand the people that made the software want to get paid for their efforts, and I think they should, but dang, it just seems a little excessiave. $500 is a far cry from $40 for tunerpro. And the thing where you have to continue to pay if you want to tune more pcm's just seems like highway robbery. Heck, the 411 is coming up on being almost 12 years old now.


I felt the same way about the '0411 software I own. I felt as if I was robbed without the mask and hand gun.

dave

[sandrock]

Biggest thing for HP Tuners is the interface. Reading OBD2 is one thing, but writing to it is another. Given the fact that a new HP Tuner kit comes with 8 license credits, you are *essentially* getting 400 dollars worth of credits and 100 for the tuner. But the funny thing is, you can't buy JUST the tuner with no credits, so I dunno.

The licensing sucks. I had to pay 200 bucks to be able to tune the PCM in my Bonneville, which is from an '05 Impala. 100 bucks went to unlocking the Impala PCM and tuning it. But once I discovered it would not allow the engine to run because it wanted to actually see a body control module, I had to flash a 2003 Grand Prix OS to it (which didn't require a BCM), so another 100 bucks. HP Tuners caters mainly to tuner shops and not the DIY'r, so their pricing tiers reflect that.

[sandrock]

Well, they say that the simplest approach is sometimes the best.

Major brainstorm. The Vortec 454 uses a 24x reluctor on the crank snout, just like the Vortec 350 and its 4x reluctor. Same firing order too. There are only two issues...the first issue is the keyway on the 24x reluctor is off slightly from the 4x, and the second issue is the 454 crank is thicker. So the 24x won't fit as it is...

...unless you attach it to the crank timing cog.

So, lets machine a shaft with two thicknesses, one for the 350 crank, and one for the 454 crank, and use that as a fitment tool to ensure concentricity. Then we fit both the timing cog (350) and the reluctor (454) on that. After finding where the 24x wheel should be in relation to where the 4x wheel would have been, we drill 6 holes through both, tap the timing cog and countersink the reluctor wheel, and attach with screws.

Thoughts????

[EagleMark]

Well yeah if the reluctor is available through GM it's still got to be cheaper than making one. Tapping it to timing chain crank gear would be another easy cheap way. But have to make sure it clears chain and ends up it right position for crank sensor.

Looking at an Optispark distributor I have here apart the cam sensor can go right where the opti sensor is mounted up or down after a cam reluctor was made. Cam relutor could be mounted by tapping hole in existing hub. Would not necessarily have to have a distributor cap or blank cap made, would it? cam sensor can be open? Dave w and MSD use open/exposed sensors. It would use existing opti distributor just like the EFI connection piece. Although theirs is enclosed, cleaner looking aftermarket piece.

[sandrock]

Well yeah if the reluctor is available through GM it's still got to be cheaper than making one. Tapping it to timing chain crank gear would be another easy cheap way. But have to make sure it clears chain and ends up it right position for crank sensor


Hence making the alignment tool. The only part to figure out would be where to clock it. On the Vortec 454, the cam sensor looks like it is mounted on the very bottom, say the 6 o'clock position, where the LT1 has it at 7:30 or 8, so the clocking will have to change as well.


Looking at an Optispark distributor I have here apart the cam sensor can go right where the opti sensor is mounted up or down after a cam reluctor was made. Cam relutor could be mounted by tapping hole in existing hub. Would not necessarily have to have a distributor cap or blank cap made, would it? cam sensor can be open? Dave w and MSD use open/exposed sensors. It would use existing opti distributor just like the EFI connection piece. Although theirs is enclosed, cleaner looking aftermarket piece.

It needs to be covered, not due to the sensor, but due to the reluctor. Should something get in its way while it's running, it won't be pretty. Likewise should the reluctor come loose, something is there to contain it. At the very least an Opti cap could go on it.

Both the sensor and the reluctor can be had through GMPD for less than 100 bucks. Not sure if the sensor will fit the LT1 cover...might very well have to buy that from EFI Connection. Even then, that's still less than 150 bucks spent for that portion, instead of spending 270 JUST for their reluctor. Consider the cam sensor build, and this can conceivably be done for less than 300 bucks, minus the coils and PCM tuning.

[EagleMark]

I don't know what you guys are using for crank sensor or cam sensor but here's one that will do both.
http://www.diyautotune.com/catalog/hall-effect-crankshaft-position-sensor-p-479.html

And a threaded version:
http://www.diyautotune.com/catalog/hall-effect-threaded-body-crankshaft-position-sensor-p-489.html

[EagleMark]

Here's a picture of Opti sensor and trigger wheel. Wheel is very thin.

[dave w]

I found these pictures on the net. Seems someone has figured out an interface to use an '0411 PCM using the LT1 sensor. http://www.weswoodperformance.com/videos/DS_III_411_PCM.wmv


dave w

[jameslleary]

just my $0.02, but i think Ford was on the ball with their EEC-4 dizzy....sequential injection, without a freakin crank sensor.

[EagleMark]

The 94 and 95 LT1 was sequential without a crank sensor because of the optispark ignition system.

[jameslleary]

yeah, but thats only for use on the LT1....Ford did it with a standard distributor. Us GM guys have to hack something together. I have often thought of doing something similar to the picture 2 posts up, and running a late LT1 ECM just so i could run sequential injection, with my TPI hardware.

[EagleMark]

1project2many just posted about sequential versus batch fire in another thread. It made me remember a conversation with a Detroit Fuel Injection engeneer who has been working on developing EFI from it's inception for GM then Ford. SFI was developed to meet EPA standards for idle and off idle. The way he described it was once an engine reaches like 1200 RPM it does not matter, injectors are firing so fast it does not make a hill of beans. More RPM and they hardly flinch at turning off, high RPM and they are just about wide open constantly. So why is SFI such a big deal?

Look at the 94-95 LT1, in 1994 it was already set to pass EPA standards for OBDII in 1997. Why they added a crank sensor in 1996? I don't know but it must have been to meet an EPA regulation because it was already sequential and met EPA emmisions without it?

[jameslleary]

I was under the impression that i would get a smoother idle and better mileage with SFI...doesnt hurt to be a little cleaner while at it too.

[gregs78cam]

The Crank sensor was probably added to augment the OBDII requirements for malfunction detection. Maybe? Well, along with establishing engine rpm without a distributor.

[EagleMark]

I was under the impression that i would get a smoother idle and better mileage with SFI...doesnt hurt to be a little cleaner while at it too.

Cleaner air is always a good thing. Who knows how far behind EFI would be if it were not forced upon vehicle manufactures to clean up emissions. SFI is a better system, but is it worth the time, effort and money to have one on an engine that never came with it? If it did get better fuel mileage would it ever return the investment?

I'm not sure idle would get smoother just because it is Sequential but here is an example of how you could tune idle. This is a stock 1995 Impala SS. The Caprice is the same, the 9C1 Cop car is the same but the same engine in a Cadillac is different? I have run them all on my Buick LT1 and can't tell the difference and data shows no difference. So why is there a difference?

I've been told the way this was tuned for cleaner emissions was by exhaust temperatures. That is why each cylinder is different, at idle there is not as much water flow and certain cylinders would get hotter. After Idle and Off Idle all cylinders run same amount of fuel. Back to why vehicle manufactures had to develop SFI was to clean up idle emissions.

[sandrock]

Been a while since I posted back to anything....life has a funny way of getting in the way of things...

Anyways, nobody local to me will touch the intake manifold as far as modding it for a distributor. The local parts maching shops will not make some prototype tonewheels for me either, as they cannot make anything for any automotive application. Sooo....back to the thinktank for me.

As far as the LT1 build is going....just found out that the engine Hawks 3rd Gen sent me ISN'T aluminum headed. They swear up and down it came from a Trans Am, and maybe it did, but that TA probably didn't come from the factory that way. But since I have it, I might as well use it. Found some 'vette centerbolt valve covers for 10 bucks on CL, so I bought those, stripped, etched, and painted them in wrinkle black. Turned out shweeeet!

[pather]

[QUOTE=dave w;2469]I found these pictures on the net. Seems someone has figured out an interface to use an '0411 PCM using the LT1 sensor. http://www.weswoodperformance.com/videos/DS_III_411_PCM.wmv

I've a 94 LT1 and new to this forum, and was wondering if the interface for getting a signal to the 411 PCM was ever achieved from an LT1 Opti and trigger? This is my 1st LT1 and I'm pretty happy with its performance but have read a lot about (and have done) the Opti replacement before finding out about the 411 PCM upgrade.

Am pretty green to this, but from the research I've done, the EFI Connection 24X conversion is the way to go, but the price of their kit is the major stumbling block, so I found my way onto this site in my search for for innovative DIY (less $) success stories as to what others have (or can be) done without spending a lot of hard earned $.

If I understand things correctly, the biggest issue is getting a crank and cam signal from the Lt1 setup to the 411 PCM, and the Opti sensor signal cannot give the proper signal, at least not without some interface, etc. Is this correct?

Does the Opti sensor and trigger wheel give crank and cam positioning signals, but the signal is just not compatible for an LS 411 PCM?

Given the last post on this thread was 4 years ago, does anyone know if the DIY solution was ever achieved? The rest of the conversion parts (outside of the 96-97 timing cover) seems to be readily available at decent salvage prices, and once the signal issue is addressed, the harness can also be converted relatively cheaply if you're open to take the time to change connectors, and even go as far as changing the PCM connectors on a LT1 harness (from LT1 to LS connectors), and adding the few new sensor connectors etc.

Any updates or feedback would be greatly appreciated.

[dave w]

Unfortunately, the system outlined earlier in this thread did not make it to market.

dave w

[pather]

Given the Opti system is been around for 20 plus years, I was hoping for a innovative DIY solution. From what I can gather, the heart of any conversion away from the Opti is the ability to use OEM cam and crank sensors to get a signal to the 411 PCM.

This would entail of mounting a 24X reluctor (machine work required) from a compatible existing OEM part, and a 1x reluctor for the cam signal (perhaps using the existing Opti base as the drive and placement base?). Anyone have any suggestions of compatible OEM parts (that could be modified) for this? This would be a combination of machining capability, but then, as I'm new to this, how/what is the process or objective to properly line up the senor to give the right/accurate placement/reading?

The EFI kit is nice, but at $500 for the base kit, and then getting a (for earlier lt1's) a 96-97 crank hub and timing cover puts the starting price of this up near $800 - $1000 before all the other parts.

[fastacton]

I think the main reason there hasn't been more development on this is the effort and expense compared to just swapping over to an LS based engine.

[dave w]

Attached are some pics of my 4x '0411 harmonic balancer mounted crank trigger.

With some forward thinking, a dual trigger wheel (cam / crank) could be designed and mounted to the harmonic balancer of a LT1 engine. I like the idea of a 24x crank trigger and 1x cam trigger which allows using the '0411 LS per coil ignition system.

dave w

[pather]

A swap is never (rarely) as cheap and easy as one might originally think. My attempt is to find a DIY (ie cost effective) solution for the innovative driveway mechanic that doesn't want to go to an all out swap given they've a solid platform with the LT1.

The 2 major hurdles are finding a OEM 24X reluctor from another application that could be modified to externally mount on the LT1 crank hub. The next thing is finding a 1x reluctor that could be modified to be mounted on the Opti (using it as the base as the 1x reluctor drive). Any ideas of what engines would have the right donor parts?

After that is where my growing (but still limited) knowledge leaves me stranded. How and what is the mounting position for the 2 sensors?

I've access to a friend with a lathe, so that will help with the keeping the fabrication cost down to a DIY budget, as well as being able to find sensors on CL or salvage yards etc.

Any help with thoughts on donor parts (year of vehicle, etc.) and mounting position of the sensors, would be greatly appreciated.

The plan (or hope) is to be able to get the required parts for under $250, which on the EFI Connections kit (which btw is a nice kit) starts at close to $550 to $600 for the basic kit, and that before timing cover, crank hub (for pre 96 Lt1's). For a pre 96 Lt1, he EFI solution really starts at close to $800 or more $, and I'm thinking that about $500 more than most DIY budgets.

[lionelhutz]

I have read of attempts to make a new reluctor wheel for the Opti that had both the 1X and 24X signals in it. Basically, it's done by duplicating the 24X pattern twice around the wheel since the cam turns 1/2 revolution for each crank revolution. Then, I think just a level conversion to the PCM would be required. The rumour is that EFI Connection attempted this and it just didn't work right.

I've also read of attempts to use the Opti signals and convert them to the 1X and 24X signal patterns the '411 PCM needs.

But, I have never found any cases of running, driving, fully working success when attempting any of these.



With some forward thinking, a dual trigger wheel (cam / crank) could be designed and mounted to the harmonic balancer of a LT1 engine.

But you can't have a 1x wheel on the crank simulating the cam sensor. The 1X cam setup switches between "on" and "off" each crank revolution.



I like the idea of a 24x crank trigger and 1x cam trigger which allows using the '0411 LS per coil ignition system.

I too would only bother doing the work if converting to a CNP setup. I already have a 96 LT1 with the 4X crank setup installed which is currently running 95 '8051 code but I can't be bothered making my own 1X cam sensor when the conversion won't use CNP.

[pather]

Attached are some pics of my 4x '0411 harmonic balancer mounted crank trigger.

With some forward thinking, a dual trigger wheel (cam / crank) could be designed and mounted to the harmonic balancer of a LT1 engine. I like the idea of a 24x crank trigger and 1x cam trigger which allows using the '0411 LS per coil ignition system.

dave w

Where does the cam signal on your set up? Is this prototype stage or is it fully functional?

[dave w]

But you can't have a 1x wheel on the crank simulating the cam sensor. The 1X cam setup switches between "on" and "off" each crank revolution. :doh:

You are correct, the crankshaft rotates 2x turns to the camshaft 1x turn. The L31 Vortec distributor mounted cam position sensor is 175.5 degrees, not a full 180 degrees.

I thought there was a place that modified LT1 intakes to accept a distributor? Maybe use a fabricated / engineered 24x crank sensor mounted to the harmonic balancer, then install a L31 Vortec distributor in a modified LT1 intake manifold?

dave w

[Lextech]

The LT1 intake is fairly easy to mod if you can weld aluminum. You cut off the EGR portion at the rear of the intake and plate it. Then use a normal SBC intake and make a template of the distributor hole. Transfer that to the LT1 intake and hole saw it for the Vortec CMP Sensor (Distributor). Cut out a plate with a hole or machine a circular boss that will fit into your LT1 intake hole. Mock up the LT1 intake on a SBC block with its oil pump installed and install the Vortec dist. Let the dist find its sweet spot and weld in the boss.

Jeff

[pather]

Found a part #12559353 for a LS1 crank reluctor wheel that might work for fab'ing a custom crank mounted relcutor, and am guessing this is the right part for triggering the LS1/411 PCM signal. However had also found some comments about (requiring?) a dual track reluctor and but this reluctor wheel (from the pictures I was able to find) is only a single (track) wheel.

Anyone able to help clarify for a newbie. Thanks

[lionelhutz]

Ya, that appears to be the right part.

I've never researched it, but the sensor must use that second opposing ring somehow. Here's a cool document.

http://www.bowlingss.com/DownLoads/Parts%20Manuals/Holden_LS1.pdf

Page #30 (35th page in document) shows the 24X pattern. You can follow the pattern on the back ring of that wheel starting with 0 degrees around the 10:30 position. That section also says there were dual tracks but no real description of how the sensor used them.

12552480 is the big block 24x crank reluctor which mounts behind the timing cover and is similar to the part EFI Connection uses. But, pictures show a dual track wheel. 10456248 is the crank sensor for this reluctor. I would think it'd have to be used with the BB reluctor to properly detect the dual tracks. EFI Connection's pictures show a single track wheel and say it can be used with the LT1 crank sensor which was originally used on a single track 4X wheel.

But, if you don't want to source the proper timing cover to fit such a reluctor behind then using an external damper hub mounted one would be your only option.

[Hog]

Ya, that appears to be the right part.

I've never researched it, but the sensor must use that second opposing ring somehow. Here's a cool document.

http://www.bowlingss.com/DownLoads/Parts%20Manuals/Holden_LS1.pdf

Page #30 (35th page in document) shows the 24X pattern. You can follow the pattern on the back ring of that wheel starting with 0 degrees around the 10:30 position. That section also says there were dual tracks but no real description of how the sensor used them.

12552480 is the big block 24x crank reluctor which mounts behind the timing cover and is similar to the part EFI Connection uses. But, pictures show a dual track wheel. 10456248 is the crank sensor for this reluctor. I would think it'd have to be used with the BB reluctor to properly detect the dual tracks. EFI Connection's pictures show a single track wheel and say it can be used with the LT1 crank sensor which was originally used on a single track 4X wheel.

But, if you don't want to source the proper timing cover to fit such a reluctor behind then using an external damper hub mounted one would be your only option.
Here is a 1998-2001 Vortec 454 L21 used in medium duty trucks. It was the 1st BBC to get both CNP(Coil Near Plug) and Electronic Throttle COntrol(ETC). It uses a 512kb PCM. It thinks its an over grown LS1 Corvette engine.
9671
9672



Yes the 1998-2001 Vortec L21 24x reluctor 12552480($20 from GM) must use the specific L21 CKP sensor 10456248($100).


This is the 24x SBC reluctor I bought for $99 on sale. It is designed so that I don't have to use the L21 CKP sensor. I can use the less expensive 12596851 CKP sensor from the 96-2000 Vortec 305/350's, that originally was used with the 4x CKP reluctor.
9666
9667
9668
.


If you drill the LT1 intake to accept a Vortec V8 distributer, you can buy one of these EFIConnection caps.
9669
9670


The L21 uses the camshaft to drive the distributer like device sometimes known as the camshaft synchronizer. It uses p/n 01104068 $284. Its pretty much a Vortec V8 distributer, which drives the oil pump, and holds the CMP sensor (1x)


peace
Hog

[pather]

Here is a 1998-2001 Vortec 454 L21 used in medium duty trucks. It was the 1st BBC to get both CNP(Coil Near Plug) and Electronic Throttle COntrol(ETC). It uses a 512kb PCM. It thinks its an over grown LS1 Corvette engine.
9671
9672



Yes the 1998-2001 Vortec L21 24x reluctor 12552480($20 from GM) must use the specific L21 CKP sensor 10456248($100).


This is the 24x SBC reluctor I bought for $99 on sale. It is designed so that I don't have to use the L21 CKP sensor. I can use the less expensive 12596851 CKP sensor from the 96-2000 Vortec 305/350's, that originally was used with the 4x CKP reluctor.
9666
9667
9668
.


If you drill the LT1 intake to accept a Vortec V8 distributer, you can buy one of these EFIConnection caps.
9669
9670


The L21 uses the camshaft to drive the distributer like device sometimes known as the camshaft synchronizer. It uses p/n 01104068 $284. Its pretty much a Vortec V8 distributer, which drives the oil pump, and holds the CMP sensor (1x)


peace
Hog

Thanks for all the info and suggestions.

I'm leaning towards drilling the LT1 intake and using a Vortec Distributor for the 1x cam signal.

So, it looks like I'm down to 2 choices for the 24x signal, which would be mounted externally - the LS1 reluctor #12559353 or the L21 reluctor 12552480. I've a few questions re orientation of the reluctor, as well as the sensor mounting.

The LS reluctor doesn't have a keyway, but there's a small hole close to the edge of the wheel (on one end of the 5 larger holes) which is between the 5 holes and the hole hat has a arrow shaped cut out in the hole. Is the small hole #1 TDC, and how would this wheel be mounted in relationship to the 1:30 position (#1 TDC) of the keyway in the LT1 crankshaft, which seems to be a indicator or reference point of some sort. Is this #1 TDC? Once the wheel orientation is correctly made, would the sensor be mounted at the 7:30 position, or some other position (as from what I can tell from a few LS pics - the sensor seems to be mounted on the side of the LS block and its not clear to me if that is also at the 7:30 position (directly opposite the keyway / 1:30 position).

The same question of orientation applies for the L21 wheel, but that one looks like its easier to figure out as it has a key way. Would it be as simple as lining the L21 wheel to the LT1 keyway position, and also using the 7:30 position for the sensor mounting? I've not been able to find anythng that shows me how/where teh crank sensor is mounted on the L21 timing cover.

There's a lot of info around and I've learned a lot in the last week, but the one issue where there doesn't seem to be a lot of clear info is this crank/reluctor and sensor mounting relationships. Once this is figured out correctly, I'm pretty much ready to finalize the design of the mounting modifications.

Thanks in advance for any help.

[lionelhutz]

I suggest you come up with an adjustable bracket to mount the sensor and then put the engine at #1 TDC and install the wheel to match the location of the bracket.

[pather]

I suggest you come up with an adjustable bracket to mount the sensor and then put the engine at #1 TDC and install the wheel to match the location of the bracket.


Thanks for the quick feedback, but I’m still not clear on what the relationship between #1TDC, the position of the reluctor wheel, and the where the sensor is mounting in relationship to this.

May be best to try and walk me thru this.

First, make an adjustable mount for the sensor. By adjustable, I’m guessing this means the mount allows for a few degrees of adjustment?

Once the sensor location is set/made, AND the engine is at #1 TDC, what is the reference point on the reluctor wheel that should be pointed at the sensor?

I was able to find a pic of the LS wheel where someone has marked #1TDC. Is the pic accurate, and is that reference point to align with the sensor (while the engine is at #1TDC)?
9693

With the BB wheel (pic below), it has a key way, so am I correct to understand that the keyway is #1TDC and the reluctor should align at that reference point to the sensor? In the pic, the keyway is at the 1:30 position (which I'm guessing is at #1TDC), and I'm guessing the sensor is mounted at the 7:30 position (as most GM timing covers seen to mount the sensor at that position)?

9694


In Dave's post #34 above, he made a reluctor and mounted the sensor at approx. the 3:30 - 4:00 position, but I couldn't tell how the wheel was positioned/oriented at #1TDC and the sensor mounting position.

[dave w]

I used a 4x crank trigger, and the L31 distributor. I'm thinking I aligned the crank position on the trailing edge of the crank trigger (its been a couple years ago since I prototyped this setup) . I set the crank sensor 50% off / 50% on the trigger wheel. I attached a couple video's of the prototype running an engine.

http://i239.photobucket.com/albums/ff290/buildabot2002/0411%20SBC/th_0411SBCCrankPosition.mp4 (http://i239.photobucket.com/albums/ff290/buildabot2002/0411%20SBC/0411SBCCrankPosition.mp4)

http://i239.photobucket.com/albums/ff290/buildabot2002/0411%20SBC/th_0411SBC-1.mp4 (http://i239.photobucket.com/albums/ff290/buildabot2002/0411%20SBC/0411SBC-1.mp4)

dave w

[lionelhutz]

The keyway is irrelevant. Put the engine to TDC #1 and then install the wheel and sensor so the sensor is aligned to the #1 TDC spot on the wheel. It doesn't matter where the sensor is as long as the wheel is rotated to match.

Yes, it appears that is the correct #1 TDC on the wheel.

On another note, you'll have to figure out how to pin or key the hub onto the LT1 engine if you're going to mount this wheel to it.

[pather]

The keyway is irrelevant. Put the engine to TDC #1 and then install the wheel and sensor so the sensor is aligned to the #1 TDC spot on the wheel. It doesn't matter where the sensor is as long as the wheel is rotated to match.

Yes, it appears that is the correct #1 TDC on the wheel.

On another note, you'll have to figure out how to pin or key the hub onto the LT1 engine if you're going to mount this wheel to it.

I think I understand this now.

I’m still undecided about which wheel to go with yet, and will decide after a little more thought into the external mounting of the reluctor, but in either case (from what I gather now) is to start with the engine at TDC#1.

My earlier assumption, given that the crankshaft keyway (usually at 1:30, at least that what I’ve seen on my most of the TDC#1 pics), that isn’t necessarily where TDC#1 is on the reluctor. TDC#1 on the reluctor is actually at the 7:30 position, which is where GM/Chev mounts the sensor on their timing covers. The keyway is opposite TDC#1 on the reluctor, and the keyway only acts to hold the reluctor in place. Is this correct?

Given I’m mounting an external reluctor, I can clock the TDC#1 point on the reluctor, to align with the sensor at whatever mounting location I chose? Is this correct?

So, on the LS reluctor, TDC#1 is as pointed out in the pic so just align the sensor and this point.

If using the L21 BB reluctor, I didn’t see a reference point for TDC#1, but given the above “assumption” of the keyway positioning at TDC#1, TDC#1 would be opposite the keyway on the reluctor, and as long as TDC#1 is aligned with the sensor, I can clock the reluctor and sensor together the same as the LS reluctor.

Gawd, I hope I’ve got this right now. If I do, this is actually pretty simple, but in my research the last few days, I couldn’t find anything on any forums etc. where there was a direct answer to this question (at least not where someone new to this could clearly understand or count on).

As for PIN'ing or keying the crank hub to mount the reluctor, I've not figured that out 100% yet. Still a design in progress, and any ides or suggestions are very welcomed.

[pather]

Hey Guys, am still looking for someone that’s able to definitively confirm the crank reluctor and sensor orientation.

So far, either I’m just unlucky or don’t know what/where to look, but there’s a lot of banter on other sites re the crank reluctor and sensor positioning, but I haven't found a post with a pic where someone comes out and says exactly where/how to position this. They say they figured it out, but then there's no pics to follow?

I was hoping for help to confirm that (once the engine is at TDC#1) that the crank sensor should be pointed at the reluctor TDC#1, and the reluctor TDC#1 is as in the pics. Given this is a custom mount, the orientation on the crank shouldn't much matter, as long as the orientation between the reluctor and sensor are matched at the reluctor TDC#1?

2 of the pics are just the reluctor with someone’s pic indicating TDC#1,

97169717
and a few of the pics of a sensor and reluctor show the sensor positioned as in the following pic.

9718
Can anyone confirm if the sensor and reluctor are suppose to be positioned like this when the engine is a TDC#1?

Appreciate any help...

[pather]

Also, this is for a 94 LT1 and I'll be modifying the intake for a Vortec Dist for the 1x cam signal. Positioning that is just having the orientation of where the rotor would point, at TDC#1?

[lionelhutz]

The document I linked gives the pattern. Confirm the reluctor #1 position yourself using GM (Holden) documentation.

[pather]

The document I linked gives the pattern. Confirm the reluctor #1 position yourself using GM (Holden) documentation.

Thanks I'll have a more in depth read of this and see if I can understand what should be done. Thanks again.

[pather]

:doh:

You are correct, the crankshaft rotates 2x turns to the camshaft 1x turn. The L31 Vortec distributor mounted cam position sensor is 175.5 degrees, not a full 180 degrees.

I thought there was a place that modified LT1 intakes to accept a distributor? Maybe use a fabricated / engineered 24x crank sensor mounted to the harmonic balancer, then install a L31 Vortec distributor in a modified LT1 intake manifold?

dave w

I starting to gather the parts for the 24x conversion and will likely be using a L31 Vortec Distributor and modifying the Lt1 intake.

Not sure what impact the above comment re the 175.5 degrees (and not a full 180 degrees) mounted cam position sensor has?

[dave w]

Not sure what impact the above comment re the 175.5 degrees (and not a full 180 degrees) mounted cam position sensor has? If you are going to fabricate your own camshaft trigger wheel, then you would need to know the factory trigger wheel measures 175.5 degrees (and not a full 180 degrees).

dave w

[pather]

If you are going to fabricate your own camshaft trigger wheel, then you would need to know the factory trigger wheel measures 175.5 degrees (and not a full 180 degrees).

dave w

Appreciate the intel Dave.

At this point I'm leaning towards modifying the LT1 intake for a Vortec Dizzy (1x signal).

I came a across a damaged Edelbrock intake for a SBC for free (right price), and will use that to build a jig for placement of the distributor hole. Once the jig is built, the plan is to then cut out the distributor hole / hold down bolt section off the damaged Edelbrock, and then cut the exact same pattern off the LT1 intake, and then put the LT1 intake on the jig insert/place the Edelbrock cut section in accordingly, and weld it in.

The jig will have a 1 3/8" tube (welded) where the distributor will come up, and the donor portion of the Edelbrock will slide over the tube and be welded onto the LT1 intake.

[pather]

I used a 4x crank trigger, and the L31 distributor. I'm thinking I aligned the crank position on the trailing edge of the crank trigger (its been a couple years ago since I prototyped this setup) . I set the crank sensor 50% off / 50% on the trigger wheel. I attached a couple video's of the prototype running an engine.

http://i239.photobucket.com/albums/ff290/buildabot2002/0411%20SBC/th_0411SBCCrankPosition.mp4 (http://i239.photobucket.com/albums/ff290/buildabot2002/0411%20SBC/0411SBCCrankPosition.mp4)

http://i239.photobucket.com/albums/ff290/buildabot2002/0411%20SBC/th_0411SBC-1.mp4 (http://i239.photobucket.com/albums/ff290/buildabot2002/0411%20SBC/0411SBC-1.mp4)

dave w

I've doing some research and found some info suggesting a 4x crank with an L31 (Vortec dizzy), opposed to 8 individual coils for the Lt1 (mines a 94, with no CKP from the factory).

Anyone have much background/experience with this? Its get rid of the Optispark and allows the engine management by a 411 PCM using an 02 Express Van calibration and Vortec dizzy (which is what the Express Van comes from the factory with).

I've got a lead on a 96-97 LT1 cover and 4x crank wheel, LT1 crank sensor, and a 96-99 5.7L Vortec dizzy, all for under $130.

Dave, you're using a carb set-up, how'd or what did you use (and do) for PCM engine management. I would be retaining the LT1 injectors.

How would this compare to the 24x/8 coil pack system as far as "bang for your buck"?

[dave w]

I'm using an aftermarket intake with 8 port injectors. I'm using a TBI throttle body, without injectors, for the TPS & IAC.

I used a Vortec L31 distributor for the cam position sensor and a fabricated crank position sensor.

My newest idea is to incorporate the crank position sensor with the L31 distributor.

Attached is my dual trigger distributor concept CAD.

dave w

[pather]

What is the advantage of going with the aftermarket intake, and TBI for the TPS & IAC. The LT1 intake has injectors, TPS and IAC already, and fab'ing the hole for the Vortec dizzy doesn't look to be that overwhelming of a task?

Will there be second sensor fitting - one for the cam signal, and one for the crank signal? That would be one neat design when you get it working!!!

What tune/calibration did you use for the 411 OS?

[dave w]

I used the 0411 on an older SBC, not a LT1, so I used an aftermarket intake with 8 injectors. The TBI throttle body for TPS & IAC was a low cost budget choice.

I used the calibration from a 2002 5.7 liter Express Van.

dave w

[pather]

How was the performance improvement? Were you able to run with a stock Express tune?

What harness did you use, and what modifications had to be done?

I was told that if using the LM7 (99-02-07) 5.3 Vortec harness, the #1 coil pinout is used for the single coil (you'd then delete the other 7 coil wires), but is there a ICM wire/connector/pinout that would have to be added?

Would going with a L31 (96-99) 5.7 harness, and re PIN using the LS PCM connector be the better way to go? It'd be tedious to re PIN, but the connectors are fairly inexpensive, but would this require less modification to the actual harness (and its not that hard as long as you had the right PCM pinout diagram to work with)?

[dave w]

I rewired a 1998 C1500 L31 "Black Box" harness identical to the 2002 Express Van L31 wiring schematic. The stock Express Van tune is a good starting point. I use EFI Live to to tune the '0411.

[pather]

I rewired a 1998 C1500 L31 "Black Box" harness identical to the 2002 Express Van L31 wiring schematic. The stock Express Van tune is a good starting point. I use EFI Live to to tune the '0411.

How was the LT1 performance improvement with the base Express Van tune?

[dave w]

How was the LT1 performance improvement with the base Express Van tune?

I did the conversion on a TBI 350 engine, NOT a LT1.
dave w

[pather]

Well, I've made the decision to go ahead with the Opti delete on the 94 Lt1 and am starting to pick up the necessary parts.

Will be doing the 4x (using a 96-97 4x reluctor wheel, timing cover, and CKP sensor - getting a great deal on this) and using a 96-99 Vortec dizzy for the 1x CMP signal and spark distribution.

Have a few questions (going with the 02 Express Van calibration) re what to use for O2 sensors, and what KS's to use?

Will the 94 Lt1 O2 sensors be compatible, and if not, what are my options (96-97 Lt1 O2's, L31 or LS or 01 and newer Vortec).

Can I run the 96-97 KS (as they will fit the LT1 KS thread), and do I need 2 KS's, or be ok with 1?

Can I retain the LT1 ICM and dual connector coil, or do I need a L31 ICM and coil?

Am assuming all the other 94 Lt1 sensors (IAT, MAP, MAF, TPS, ECT) will be compatible?

Advise/previous experience re this is greatly appreciated. Thanks

[Rocko350]

If your running headers and not manifolds, run 01 corvette secondar o2 sensors in the normal, primary position you need them in and repin your vehicle side harness not the sensor side of the harness to make them work. search ls1 tech for reasons why.

Switch to the l31 coil/ign module. knock sensors whould be from the 02 g3500 with 5.7 the original lt1 sensors are most likely worn out at this point and you need to flush the block properly anyway. Use liquid pipe sealer not tape if there is no preapplied sealer on the threads. use 2 sensors.

The rest of the sensors should be GTG. There will be area scalers and values to change before first fireup. We'll cross that bridge then. Idle air handling is no where near what your used to seeing on the lt1.
Fuel pressure for the injector constant is 4 bar not 3 bar like the lt1.

Lots more.

Get to work, we need pics..

Chris

[pather]

I'm running headers and will be using the 94 LT1 harness and re pinning it at the PCM connector side with the LS PCM (blue/red) connectors. Will add wires for the CKP (the 94 LT1 does not have the CKP) and changing other pigtails as necessary.

Did some research on part numbers and the 94 LT1 ICM and coil, and the numbers are different from the 96-97 Lt1, however the 96-97 Lt1 and L31 share the same ICM and coil numbers. The difference is a change from a dual connector (94 Lt1) to a single connector (96-97 Lt1 & L31). Outside of the connector, I'm not sure there's a change in the coil (given I'm re PIN'ing the 94 LT1 engine harness, I should be ok with the 94 LT1 coil, or NOT)? With the ICM, I've read where there are guys saying there's a difference between the 94 Lt1 ICM's and the 96-97 ICM, and then there are guys that say there's really no difference and they're interchangeable.

Anyone know for sure? Is the difference in the sensors/parts something that can be dealt with when doing the PCM re-flash (ie give the info to the programmer, and he'll know what to do)? That's the thing I'm finding - the more research/opinions I find, the more certain things are clearer, and there's also more differring opinions/experiences on other parts compatibility questions.

As for the KS, I'll go with the L31 KS. There was no correlation between the any of the LT1 KS part numbers, and the L31 KS part #.

Also re the CKP sensor, the 96-97 Lt1 and the L#1 share the same 4x reluctor wheel, but the crank sensor part # for the Lt1 CKP sensor and the L31 are different. However the L31 share the CKP sensor part # with the LS1, but the LS1 is a 24x, not a 4x. From what I've read, a 4x sensor will not work for a 24X system, and visa versa?

Re fuel injectors, am I ok to stay with the 94 Lt1's (they also share the same part # thru to the 97 Lt1) but I've not found anything re if the 411 PCM will require a different injector?

I've collected some of the parts, and still trying to clarify some of the parts I should go with. Doing this in a tight budget, so hoping to get the parts right the 1st go around.

I'll get some pics up as soon as I start the dis-assembly, but that's probably going to be a couple weeks yet. I did manage to score a damaged SBC Edelbrock Performer 2101 intake (for $0) which I'm going to use as a making a template for the Vortec dizzy hole for the LT1 intake. Once the template is ready, am going to cut out a portion of the Edelbrock rear section where the dizzy hole is, and cut out the correlating section in the LT1 intake, and weld the Edelbrock section in.

It sounds like you've experience with this, and I appreciate your feedback. btw is there anyone on this forum that would be able to flash a base tune that I could run with until have the $ to get it on a dyno?

[pather]

Well yeah if the reluctor is available through GM it's still got to be cheaper than making one. Tapping it to timing chain crank gear would be another easy cheap way. But have to make sure it clears chain and ends up it right position for crank sensor.

Looking at an Optispark distributor I have here apart the cam sensor can go right where the opti sensor is mounted up or down after a cam reluctor was made. Cam relutor could be mounted by tapping hole in existing hub. Would not necessarily have to have a distributor cap or blank cap made, would it? cam sensor can be open? Dave w and MSD use open/exposed sensors. It would use existing opti distributor just like the EFI connection piece. Although theirs is enclosed, cleaner looking aftermarket piece.

While I’m waiting to pick up the parts, I’ve had some time to go back and re-read some earlier posts on this forum and a few other forums, and some of what didn’t make a lot of sense, makes more sense now. I’m still pretty new to this but have been on a pretty good learning curve.

I’m picking up the 96-97 LT1 timing cover and 4x reluctor in a few days, and might also be able to get my hands on a used L21 24x reluctor for $10. The possibility of the L21 reluctor got me thinking about the decision of a “4x or 24x system” again, as the major reason earlier for leaning to the 4x was the part(s) were already available on the 96-97 LT1 (and putting this on a 94 Lt1 was relatively a bolt on).

I went back to the earlier post by Sandrock and Eaglemark re the L21 reluctor, and now understand what he was trying to do, but the focus on that discussion got to a point, and then dropped off.

I want to take one last look at whether a 24x may be do-able on a tight budget. I can get a set of 8 coils for under $50 (and I understand the L21 wheel must go with the L21 CKP sensor), so my budget shouldn’t take a huge hit. The only other variable is the tuning and whether there is much difference in cost between a 4x and 24 to base tune and or dyno?

The questions with the L21 reluctor are (1) the ID is 1.6” whereas the SBC/LT1 is approx. 1.25” (2) the thickness of the L21 (from what I’ve read) is thicker than the Lt1 4x reluctor and (3) is the OD of the LT1 4x and L21 4x reluctors the same?

Sandrock had looked at fab’ing a centering tool and bolting the L21 reluctor to the crank gear, but there were concerns whether the bolts might interfere with the gear operation, and it wasn’t clear if the alignment and clearance of the reluctor inside the timing cover would be ok – both due to the extra thickness of the L21 reluctor. Then there is the final issue of the orientation/placement of the sensor. I had asked the sensor placement/orientation question earlier in this thread, but being a newbie still, can’t say I 100% understand how to do that properly (yet).

The idea of trial and error and what is entailed with “re and re” to do a trial and error, was the reason for leaning to the 4x. I don’t have the equipment to do a bench test to see if the sensor orientation/placement on the reluctor is correct before installing it. If somehow I can figure that out definitively, then this is what I’m considering with the L21…

Take the Lt1 reluctor and turn it down to 1.6” OD and press the L21 reluctor onto the Lt1 reluctor base and tack weld it in place. This would be done on a lathe to ensure run out and concentricity. But before tacking it in place (as long as the thickness and OD issues were ok/resolved) I’m back at sensor orientation/placement question. The LT1 timing cover having the sensor boss at the 7:30 location, I would have to make sure the L21 reluctor was properly oriented before tack welding it in place (ie using the keyway on the 2 reluctors as a guide apparently is not 100% accurate or right).

What do you guys think, or has this been thought out before, and is not do-able?

[dave w]

Considering the steep learning curve (first time challenge with this type of conversion), I think using the 4x system would provide a more affordable and simple path to success.:thumbsup:

[lionelhutz]

How much will you have invested by the time you buy the L21 reluctor wheel and sensor and do the machining work? Also consider how much you have to spend again to get a working setup if it doesn't work. $150 gets you a working 24x wheel that simply replaces the 4X LT1 wheel.

Tuning would cost the same either way.

I have no idea if you could make the L21 wheel fit and work on the LT1 engine. If you try the machining work, you would probably want to machine out the L21 wheel to have a larger ID before trying to mate it to the center of the 4X wheel. Otherwise, you're talking about cutting the center of the 4X wheel down to 0.175" thick and I'd think that thin a piece could easily distort or break at the keyway. The orientation would require careful measurement but isn't that difficult. The TDC on cylinder #1 should correspond to one of the tooth edges on the 4X wheel. So, align the TDC #1 tooth of the 24X wheel at the same spot. A picture was already posted with the TDC #1 cylinder tooth edge on the 24x wheel. You do it all relative to the keyway slot of the 4X wheel so the new wheel tooth is in the same location as the old wheel.

As I posted before, I wouldn't do the swap unless it included CNP. Going as far as you're going, I'd just spend the extra $150 to do the 24x setup.

[pather]

How much will you have invested by the time you buy the L21 reluctor wheel and sensor and do the machining work? Also consider how much you have to spend again to get a working setup if it doesn't work. $150 gets you a working 24x wheel that simply replaces the 4X LT1 wheel.

Tuning would cost the same either way.

I have no idea if you could make the L21 wheel fit and work on the LT1 engine. If you try the machining work, you would probably want to machine out the L21 wheel to have a larger ID before trying to mate it to the center of the 4X wheel. Otherwise, you're talking about cutting the center of the 4X wheel down to 0.175" thick and I'd think that thin a piece could easily distort or break at the keyway. The orientation would require careful measurement but isn't that difficult. The TDC on cylinder #1 should correspond to one of the tooth edges on the 4X wheel. So, align the TDC #1 tooth of the 24X wheel at the same spot. A picture was already posted with the TDC #1 cylinder tooth edge on the 24x wheel. You do it all relative to the keyway slot of the 4X wheel so the new wheel tooth is in the same location as the old wheel.

As I posted before, I wouldn't do the swap unless it included CNP. Going as far as you're going, I'd just spend the extra $150 to do the 24x setup.

You're 100% right about the cost. I wouldn't be considering this if I wasn't on a tight budget, and the fact that the machining etc. is a zero cost thing for me.

I've got the parts (timing cover, 4x reluctor, 24 reluctor, vortec dizzy, L21 CKP sensor, LT1 CKP sensor,) for just under $125. Am expecting to get a used the 8 coil pack for $60 - $70. Would re-PIN the Lt1 harness with LS PCM connectors. Have somebody welding the Lt1 intake for the Vortec Dizzy for $40, so all in, I'm hoping to be done (before tuning) for about $325 for parts, gaskets, etc.

Was thinking about opening up the L21 reluctor for the very reason you mentioned. Once I get the parts, then it just waiting for my buddy to have time on the lathe.

I just figured given I would have to open up the 94 Lt1 for the 4x reluctor install, I would give this 24x reluctor idea another shot. Be a shame to go in that deep, and then decide the 24x is the way to go.

It might be a few weeks, but I'll update etc. when I get into this (waiting for my buddy's schedule is the unknown). Thanks for the input re the reluctor/sensor orientation. That was my last "what to do about that" question before changing back to the 24x system.

[pather]

I’ve almost all the parts for the 24x conversion now. Besides finding time to work on this, I’ve a question re the positioning of a LS2 CMP sensor before starting the teardown.

Am designing my own 1x CMP signal using a LS2 Cam Gear concept (details of unit etc to come). My question is where/how to position the CMP Sensor (part # 12591720) in relation to the raised portion of the Cam Gear trigger.

Have attached a pic with 2 drawings. The green section is the raised trigger on the Cam Gear, and the pink circle is the CMP sensor. Drawing “A” has the trigger leading edge at edge of the CMP sensor at TDC 1, and Drawing “B” has the leading edge at the center of the CMP sensor at TDC1.

Which is the correct positioning?

10199

[pather]

Just checking in to let you guys know that the plan is still going ahead with the 24x conversion. Between work, and life in general, its been hard to find the time. Have assembled most of the parts (just a few connectors/pigtails, and the coil pack left), and waiting until I've the budget for the tuning software before starting into the conversion.

Will update...

[black_bear10]

Doing the same retrofit. Has anyone figured out the BBC 24x reluctor wheel phasing to the SBC?

[pather]

Doing the same retrofit. Has anyone figured out the BBC 24x reluctor wheel phasing to the SBC?

I've completed the fabrication and machining for a DIY CMP, and a L21 24x reluctor. As soon as I have time to install (hopefully between now and Xmas), I'll report back.

[black_bear10]

I've completed the fabrication and machining for a DIY CMP, and a L21 24x reluctor. As soon as I have time to install (hopefully between now and Xmas), I'll report back.


Please keep me posted!

[sherlock9c1]

I have read of attempts to make a new reluctor wheel for the Opti that had both the 1X and 24X signals in it. Basically, it's done by duplicating the 24X pattern twice around the wheel since the cam turns 1/2 revolution for each crank revolution. Then, I think just a level conversion to the PCM would be required. The rumour is that EFI Connection attempted this and it just didn't work right.

I've also read of attempts to use the Opti signals and convert them to the 1X and 24X signal patterns the '411 PCM needs.

But, I have never found any cases of running, driving, fully working success when attempting any of these.
Bringing this back from the dead, as I was pondering. Making a CAD drawing of a revised optispark trigger wheel with the 24x or 58x crank and cam patterns is quite possible, and the optical sensor is an active component much as the LS CMP and CKPs are; anyone seen more info on WHY these output signals were not playing nice with the 0411 PCM?

[bk2life]

………… Few years from now you could probably buy an LS engine car or truck for $2-3000...
I buy several from the local u-pullit lot complete without wiring and no ac compressor, $375 with a warranty. There are even days where you can get 15% off !

[sherlock9c1]

Update - I did speak with the owner of Torqhead and he had real good reasons for not continuing to use the optispark in any form, though he didn't think what I proposed was beyond possible. EFI connection did not provide any information but given the quality of his products, I'm sure he chose not do use the trigger wheel for a valid reason.

I did get my first project car back on its feet yesterday; time to work on the next one, then I have time to play with this more.16341