LT1/0411 PCM/Opti Delete

[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.





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,

Attachment 9716Attachment 9717
and a few of the pics of a sensor and reluctor show the sensor positioned as in the following pic.

Attachment 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]

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.





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)?