302 cubes for Suburbia

[1project2many]

I've picked up a 99 Suburban with a bad engine to replace our 95 Blazer. It would be easy to replace the crank, rod, and bearings and put it back on the road with the original 350 but I've had this purple 302 sitting in my barn since '04 waiting to be installed in something. The 302 was originally built for the S10 and had a ZZ4 cam but for Suburbia I need a lower rpm torque peak. After many, many late hours I believe I've accurately modeled enough components to put something together. Here's the configuration:

L31 four bolt main block, L99 crank and 5.97" rods, H631CP pistons at .030" = 306 ci
L31 heads, stock valves and ports, guides machined for over .525" lift and upgraded LT1 springs
9.0:1 compression
14097395 HT383 cam
1.6 rockers
.040" quench
Single roller timing chain
small harmonic balancer
shorty OBX headers
Mercruiser dual plane ceramic coated EFI manifold

Still working on...
Torque converter choices
Exhaust configuration

The simulation shows one of the roundest torque curves I've ever seen.

[JeepsAndGuns]

Ok, this has nothing to do with the post, and its just out of curiosity because I have seen it on another screen shot of yours.
Seamonkeys?

[1project2many]

Seamonkey. No "s". Internet browser. I used Netscape for years. Netscape code was eventually released to open source and formed the basis of Mozilla. Mozilla was distributed as a standalone browser for a while but was eventually dropped in favor of Firefox. Firefox changed the look and feel of Mozilla considerably so a group of developers decided to continue along a path closer to traditional Netscape / Mozilla with Seamonkey. I have both browsers on this machine and although they use much of the same code, Firefox feels foreign to me.

[EagleMark]

edit...

Just me but sounds like a lot of work and expense for a daily driver.. what about smog there? You should rebuild the engine in the Surburbia and send me that intake... :innocent2:

[JeepsAndGuns]

Seamonkey. No "s". Internet browser. I used Netscape for years. Netscape code was eventually released to open source and formed the basis of Mozilla. Mozilla was distributed as a standalone browser for a while but was eventually dropped in favor of Firefox. Firefox changed the look and feel of Mozilla considerably so a group of developers decided to continue along a path closer to traditional Netscape / Mozilla with Seamonkey. I have both browsers on this machine and although they use much of the same code, Firefox feels foreign to me.

Wow, interesting. Never heard of seamonkey web browser.
Back to your thread, sory about the hijack.

[1project2many]

Suburban's not going to be daily driver. It's the luxo-liner when we take the kids for long trips and it's the tow vehicle that's finally large enough to haul the stuff I put on the car trailer. I'd have to build a turbo four and still keep it below 55 to afford it as a daily.

The 302 is already built. I'm just changing the cam (and shortening the balancer, and adding the crank sensor, but no big deal there). Smog is easy here. Plug state computer into OBDII port. If computer sees enough readiness monitors and doesn't see codes, then all is good. I don't believe I'll have any problems with that. LS engines use a divorced EGR so I can follow that path here. I have to connect the purge line somewhere but that's not likely to be an issue, either.

Besides, using the 302 in Suburbia frees up a set of Vortec heads. I'll swap in a set of 2.02/1.60 stainless valves I have here from some faulty Bowtie heads, throw on a set of big springs, bolt them onto the old school roundy round car block with a big Lingenfelter retrofit roller cam that's hanging around and put the Chevelle back on the road with the other marine intake I've got and the six speed that's been collecting dust since '03.

Also, if you watch Ebay there are Vortec style Marine intakes that show up from time to time. Prices are a bit steep for me but they're still cheaper than some of the aftermarket L31 intakes.
http://www.ebay.com/itm/310473716029?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

[EagleMark]

So what engine was in the Subrban? Or more importantly what PCM? Didn't 99 come with Vortec and LS engines (still badged Vortec)?

That is a strange tourque curve, really opens up gear choice, what's in it and where will it be running RPM wise?

[1project2many]

This has an L31 5.7 right now. Pickups changed body style in '99 but Suburban waited another year. Rear gear is 3.42. Here's the highway speed vs engine speed chart with the current tires.

Vehicle RPM RPM
Speed Drive Overdrive
55 2040 1420
60 2225 1549
65 2410 1687
70 2596 1807
75 2781 1936

When these tires wear out I'll probably switch from 245/75 16 to 225/75 16 which is what we run on most of our fleet vehicles. They're 29" tires vs 31" so the highway rpm will increase a small amount.

Torque curve comes from ability to run successive models with changes like header primary length, intake runner length, collector length, etc so I was able to look at what products were available and do my best to model the same parts in software. Every comparison I ran showed no matter what cam, the short stroke / long rod engine liked short intake and exhaust lengths for maximum torque between 1500 and 4500 rpm. Long headers fell very short after about 2k but came back strong starting about 4500 and mid length had a weak area from 3k to 5k. Stock L31 and other long runner intakes boosted torque to about 2500 but really died after that. For max power the dual plane intake doesn't have enough plenum volume but for the truck it's sufficient.

[EagleMark]

Looks like plenty of torque for driving.

Have you played with this PCM yet? Lack of parameters is unimpressive to say the least. I think it was given up on as a 5600 RPM limit has not been broken. 0411 PCM swap is popular.

[1project2many]

Almost all of our one ton GM vans use black box pcm's. I'm ok with the system's limitations. I believe main reason for giving up is Jet DST seems to be losing popularity war and HPTuners doesn't do much with black box. For many trucks the black box is more than sufficient but on forums they seem to think you need all the bells and whistles just to start and drive.

[EagleMark]

EFI Live and TunerCat/RoadRunner OBDII both handle them. Actually TunerCat has more usable paremeters.

I don't need a swap but have hit a 16 MPG highway wall, so I'm swapping to 0411 for the Lean Cruise.

[1project2many]

I've got an 0411 at the shop if I want to swap out. It's funny that you mention 16mpg... that's what our S10 Blazer got with the 4.3 and 3.42 gears. I told my wife "If we're going to get 16mpg we should at least have enough room to breathe."

The code for the black box has been partially disassembled and made public. I believe fast355 from thirdgen posted a copy. It may not be the best one to work with but I don't know of any others that are this far along. It's kind of like the 7747 was in the beginning.

[EagleMark]

I've got a couple 0411 to use but thanks for the offer. Or did you need on?

Shouldn't an S10 get better then that? I got a Suburban that gets' 15 around town?

There's a Vortec Hack here somewhere from Dimented247 is the only one I have seen. But others have done it too and still gave up because they can't beat the 5600 RPM limit? With the engine having injector issues and no aftermarket intake it ended up a dead horse.

I think it will be fine for you except the last bit of HP in your simulation looks to be a few hunder RPM short. Since your not building a race car, but a tow rig? Who Cares?

[1project2many]

I'm just saying that I've got the parts for a pcm swap if I need it.

Blazers are 16-18mpg. These are 4200-5300 lb vehicles that sit fairly high being powered by a 4.3 so they generally don't do that well. This last one was our 4th starting with an 86 or 87 TBI. Best mileage I was from 4.10 gears swapped into a 91 4.3 TBI which would net 20 or so on long trips. Maybe the last ones before the Trailblazer got better but I don't think so.

I'm sure the hack you're talking about is the same one I have. I've only ever seen one. Funny how people gave up on the Vortec intake and pcm but still work with TBI. Stock L31 setup can make over 400hp before larger injectors are needed. Seems like plenty of power for many trucks. It's good for torque so a 383 or 400 with low end cam that can pull stumps would be a great choice. TPI was the same way and people are still playing around with that one. I think the surprise of finding the rpm limit was big news. If you accept the limit and build accordingly then you won't be disappointed.

[1project2many]

So the build is moving along but not without hiccups. First was timing chain. I built the engine not expecting to use a crank sensor then had to switch over. Took several tries before I got the heavy "truck" roller chain. Then the dang key issue. LT1's use a non-keyed balancer hub so the woodruff key is notched so it won't engage the balancer hub. I forgot I had that key in place and couldn't for the life of me determine why I couldn't get the crank reluctor wheel to engage the key. Then the timing cover issue. Turns out this isn't the L31 block I'd though it was. The timing chain area is missing extra material for the modern plastic cover to seal against. So I just finished making an adapter to sandwich in between cover and block. Next is to get the coolant straightened out with bypass holes if needed.

<sigh>

[EagleMark]

I'm sure the hack you're talking about is the same one I have. I've only ever seen one. Funny how people gave up on the Vortec intake and pcm but still work with TBI. Stock L31 setup can make over 400hp before larger injectors are needed. Seems like plenty of power for many trucks. It's good for torque so a 383 or 400 with low end cam that can pull stumps would be a great choice. TPI was the same way and people are still playing around with that one. I think the surprise of finding the rpm limit was big news. If you accept the limit and build accordingly then you won't be disappointed.Oh I agree! They will do what a truck needs.

But still can't shake the 16 MPG highway with the Vortec but can hit 18+ with a TBI? I've only read that a 0411 swap with lean cruise will do 21... we'll see soon.

[1project2many]

Well... after another week of crazy late nights and a marathon session at the shop yesterday I got to hear the 302 run. For about 10 seconds. Turns out I've got something wrong inside the engine. I've built quite a few engines over the years and except for the first one I ever tried to build back when I cashed my paychecks at the liquor store I've never had a major problem. But this thing's turning pushrods into modern art in just two or three crank revolutions. My guess right now is that either the pistons were installed on the rods incorrectly and I didn't catch it, or they were installed correctly but I flipped the rods 180 degrees. Either scenario would put the valve reliefs on the wrong half of the piston. Very frustrating. I just ordered a cheapie reman crankshaft for the 5.7 that came out and I'll be putting in more late nights putting that back together and back into the 'burb so we can use it for Christmas. Then I'll dig back into that 302 and see what the $%^ I messed up.

[EagleMark]

Well that sucks! Especailly when you know better. I went through a bunch of pushrods with a big cam on my first motor build in high school. Didn't know anything about releifs back then...

[dave w]

Well, I have a similar not good engine rebuild experience to share. See pics below.:mad1: SBC 406, 6.0" rods.

dave w

[JeepsAndGuns]

Dang dave, what happened to that thing?

[1project2many]

Thanks for sharing. 406 parts aren't cheap especially with those long rods.

What's the pink stuff?? Obviously something hard enough to do damage. Piece of a bolt or screw that got sucked in?? Is that groove too deep to run?

[dave w]

The engine was fresh from the machine shop, which also assembled the engine. It appears to me, something foreign was in the ring compressor when the piston was installed into the engine. I'm requesting the machine shop sleeve the damage cylinder, at their expense.The machine shop insists the cylinder only needs a hone. Drama, Drama, Drama, I can't say I want to do business with a machine shop that is reluctant to fix the problem the way I think the problem should be fixed.

Anyway the first picture shows how the piston valve reliefs should be installed.

I'm not sure what the pink stuff is, paint from the rings or maybe assembly lube?

dave w

[1project2many]

Dave... Are you saying it's part of a ring compressor?? For 4" bore engines I have a nice, adjustable tapered aluminum compressor that I use. I'll be using it tomorrow if all goes well.

Pulled heads and pan but left the block in the truck. Pistons are installed backward. Rods, however, are installed correctly. So the machine shop assembled pistons to rods incorrectly but I'm still a bonehead for assembling it this way. I built the engine between the time I injured my back and the time I had surgery and all I can figure is the pain killers I was taking had something to do with it. It's no excuse but I can't see any other way I'd let something so obvious go. So tomorrow am I arrive at work early and knock the pistons out. During the day I'll either send the rods/pistons to another shop or try my hand at disassembly / reassembly using a torch to loosen the pressed pins. Hopefully the local GM dealer will have the head gaskets I used in stock so I don't have to wait for those. Part no 10105117 .028" compressed thickness.

Now I have a 45 minute drive ahead of me to get home so I can catch a few hours sleep and be back up at 4:30 to head back to the shop.

List of things to bring in from home tomorrow:
Tapered Ring Compressor,
Coppercoat
Toaster oven for heating rods
Patience, patience, patience.

[dave w]

Dave... Are you saying it's part of a ring compressor??

I'm thinking some debris was on the ring compressor. Who knows where the debris came from, maybe the debris was in a shop towel that was used to wipe the ring compressor? Maybe the debris was on the shop table where the ring compressor was set down between pistons? I don't think the debris is from the ring compressor, most likely the ring compressor picked up the debris from somewhere just before compressing the rings?

dave w

[EagleMark]

Dave... Are you saying it's part of a ring compressor?? For 4" bore engines I have a nice, adjustable tapered aluminum compressor that I use. I'll be using it tomorrow if all goes well.

Pulled heads and pan but left the block in the truck. Pistons are installed backward. Rods, however, are installed correctly. So the machine shop assembled pistons to rods incorrectly but I'm still a bonehead for assembling it this way. I built the engine between the time I injured my back and the time I had surgery and all I can figure is the pain killers I was taking had something to do with it. It's no excuse but I can't see any other way I'd let something so obvious go. So tomorrow am I arrive at work early and knock the pistons out. During the day I'll either send the rods/pistons to another shop or try my hand at disassembly / reassembly using a torch to loosen the pressed pins. Hopefully the local GM dealer will have the head gaskets I used in stock so I don't have to wait for those. Part no 10105117 .028" compressed thickness.

Now I have a 45 minute drive ahead of me to get home so I can catch a few hours sleep and be back up at 4:30 to head back to the shop.

List of things to bring in from home tomorrow:
Tapered Ring Compressor,
Coppercoat
Toaster oven for heating rods
Patience, patience, patience.That story just sucks...:rolleye: How long has that motor been sitting waiting for a home? What a bummer...

How exactly does a machine shop press these in? They don't use heat do they? Torch on new pistons and rods scares me... Or do you not have a press?

I hate to say this but are the valves OK? Back in 1977... yup I'm old... I bent 2 sets of pushrods and didn't hurt a valve. I even pulled timing chain cover to see if I had it wrong, before I realized I built it wrong .

Man I'm sorry, that is a bummer. Like you said PATIENCE!!! Sounds like your tired to boot... patience...

[JeepsAndGuns]

How exactly does a machine shop press these in? They don't use heat do they? Torch on new pistons and rods scares me... Or do you not have a press?


All the ones I have seen, have either a gas fired or electric heater that heats the small end of the rod enough to ease the insertion of the pin. AFAIK, they still press them in as they are quite a tight fit. I can understand why they are such a tight fit too, last thing I would want is to have a pin walk out once the engine got up to temp.

[EagleMark]

I can see heating the rod before pressing it in. And even freezing the pin for ease of install. But taking them apart to reuse parts? That's touchy... I've done a lot of carrier bearings on my press and have watched it bow before the bearing starts to slide on. Doing this with a piston I want to reuse would raise my blood pressure! I'd have to make some kind of jig to hold piston. Never actually watched it done at machine shop...

[POZE]

When working in a GM dealer in the late 70s early 80s , one of the required special "J" tools was a fixture made to press out wrist pins. We did use it and had good luck but it sure isn't the best way to install wrist pins. Using the electric heaters the machine shops have is the best answer.

[1project2many]

Actually pressing pins out can be tricky. As mentioned, proper support for the piston is critical and it's not unheard of to do damage during the process. It's not a job I like to do if I don't have to.

Judicious application of heat to the small end of the rod and quick action after heat is applied works to get the pins out without a press. The trick is to apply the heat quickly but not in so small an area that damage is done. It's best if the rod is heated without discoloring but most of the time it turns some shade of blue despite best efforts. That's just the way it is.

Luckily I didn't have to worry about that because I was incorrect... the pistons are oriented properly. I thought they were wrong last night (yes, I was very, very tired when I posted) but for some reason I decided to check another engine I have this morning and realized I'd made a mistake. At this point I'm kind of stumped. All I can figure is the valve springs are too stiff and the pushrods are collapsing. I've checked everything I can think of to check including the lift on the cam in case GM sent the wrong one. I don't see any collision marks on the valves or pistons. The valves aren't bent and they're sealing well. The guides have been machined for more lift than stock and there's no sign the spring retainers made contact with the seal. The pushrod holes in the head have been opened up for the 1.6 rockers and anyway the problem is there with stock rockers. The springs appear good for over .540" lift and the max this cam generates is .480", which is small. I have no way to test spring pressure so I'm out of luck there but I believe they are K-motion K-750 springs (http://www.jegs.com/i/K-Motion/571/K-750/10002/-1) which are a fair amount higher pressure than the LT4 spring (http://www.sallee-chevrolet.com/Camshafts/lt4hotcamkit.cfm) that GM uses on most crate engines. I'm going to replace the springs with stock L31 springs, install a couple more pushrods, and try it again. Not sure where to go if this doesn't work. This is a near stock, mild build and I shouldn't have issues like this.

[POZE]

I have heard of valve spring bind but sounds like you checked that.

[1project2many]

I did check for valve spring bind. And there was none. Except... there was bind.

Turns out that my machinist friend and myself both failed to notice the damper springs had to be removed. The L31 valve guide is machined so it closely fits the ID of the stock springs in order to damp oscillations. Well, the ID of these springs matched the stock L31 parts and the OD of the damper was the same as the OD of the guide. Can't put two pieces of matter in the same space at the same time. But because it was inside the primary spring I never noticed it when I was checking the primary coils for contact on the vehicle. It was very good to find this, although it would have been much better to find it before I did damage. So I'm out the cost of a set of GM performance head gaskets (about $36) and a ton of time. Engine starts and runs.

Right now I'm sitting and waiting for silicone to cure at the timing cover. The adapter I built to run the Vortec plastic cover spaced the cover forward about 1/16 inch roughly. This put a little extra pressure on the lower portion where the pan gasket sits. All the parts sealed tightly. But as the engine warmed up the cheap plastic cover decided to change shape slightly and conform to the pan which left a small gap at the pan/block/cover intersection. No problem. We've got some really good sealer here so I filled 'er up. In a few minutes I'll fire it back up, do a crank relearn, check the distributor / cam sensor position, and I'm outta here.

[EagleMark]

Well I'm glad that's over! :rockon:

[1project2many]

Drives ok so far. Mostly highway. No surprise that off the line pull isn't strong but on the highway there's plenty of go. Had to decrease cranking PW to match smaller engine displacement to help startup. Also have a slight hunting idle when warm in gear, possibly due to reduced loading from higher stall converter. Reduced spark corrections for idle speed by .9 across the board to see if this helps. Fuel economy seems reasonable by seat of the pants but I haven't done enough driving to get real numbers. And, the engine's still brand new so it will change some anyway.

[1project2many]

As I have time I play with the truck. It's not often, as my handle implies. Warm restart is a beech. I've tried looking at 305 cals for hints as to what GM did for the smaller engines but there are enough differences here that a simple comparison doesn't reveal enough answers.

I really need to get better scantool data. The free software I'm using in my laptop tries to display basic data but what I get is not enough to tune with. I don't even have IPW. I can swap to the 0411 but I get stubborn about things sometimes and I'm feeling like fighting with this one for a bit longer. So I guess the next step is to get the shop's Modis involved and see what's available in the "official" datastream. If some of the data I'm looking for is there I'm going to have to see about implementing it in the free software.

Lots to do, lots to do. And we're already a week into June!

[Hog]

Nice to see that you built the L99 based 302. With teh L31 heads/ and Ramjet 350/HT383 cam on only 302 cubes, it should make some decent power, and at a higher rpm.

How does it feel compared to the 350? Does te power peaky at all?

If you had to do it all over again, would you simply do a 305?

Interesting manifold, I wish you were close so you could try my my Merc cross ram intake on it.
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/CASTINTAKE_250_161.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/CASTINTAKE_250_161.jpg.html)


On your intake, I have to wonder if the single 75mm t-body on your 4 hole intake is playing havoc with airflow? I would find it hard not to machine that out to match the 75mm truck t-body.

Are you running the stock 1 7/8" L31 1/2 ton headpipes?

1/2 ton and 3/4 Vortec 350 headpipes side by side
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/L31exhaustfront.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/L31exhaustfront.jpg.html)

I would love to see a chassis dyno report on this beast once you get it all smoothed over.

PS I might be tempted to dump a stock L30 305 calibration in it obviously corrected for the correct IFR of your injectors. What are your flowing and at what pressure? What are you using for a fuel pressure with the vacuum refernce disconnected?

Good work.

peace
Hog

[1project2many]

Right now I'm still using the stock L31 intake. I chose to install it during the initial engine install to save time and my plans are to install the dual plane in the future.

305 calibrations are almost always a poor match for 4" bore engines. For some reason the 305 is much more detonation prone. The L30 is better than the L03 but you can still see the changes both in the spark tables and the knock retard when compared to the L31. Between the longer rods, slightly lower compression, and different cam this engine is definitely in need of it's own spark map.

As I dial in the spark map I find the engine like to launch off the line, lose some acceleration in the middle, and then pull again near top end. That's no surprise as dyno software predicted that behavior. I lose some of the advantage of the long runner intake because of the loose converter but it's still usable. Next weekend I'm going to be towing a trailer with a compact diesel tractor through a 150 mile trip so I'll have a better idea of how it feels under load. Ultimately I want it set up with the dual plane and any impressions with the stock intake are just for perspective.

I am running stock exhaust after the headers. I've looked at changing them but unlike OEM, the aftermarket stock replacement exhaust systems I've looked show no difference between 1/2 and 3/4 ton models. I have plans to get down to the exhaust shop and have a new system built front to back but that might not happen until August.

As to running a 305, no. The L31 is so common that I'd buy one used before installing the 305. I built the 302 years ago to do it, and because I thought it might be a good choice for an S10 Blazer. I've been dying to use it since and when I replaced the last Blazer with the Suburban, I found an opportunity to try it. If I were to build a long stroke, small bore engine I'd probably throw a 400 crank into a 350 block. IIRC that works out to about 338 cubes and it might make an interesting torqu engine with very good emissions.

[Hog]

Right now I'm still using the stock L31 intake. I chose to install it during the initial engine install to save time and my plans are to install the dual plane in the future.

305 calibrations are almost always a poor match for 4" bore engines. For some reason the 305 is much more detonation prone. The L30 is better than the L03 but you can still see the changes both in the spark tables and the knock retard when compared to the L31. Between the longer rods, slightly lower compression, and different cam this engine is definitely in need of it's own spark map.

As I dial in the spark map I find the engine like to launch off the line, lose some acceleration in the middle, and then pull again near top end. That's no surprise as dyno software predicted that behavior. I lose some of the advantage of the long runner intake because of the loose converter but it's still usable. Next weekend I'm going to be towing a trailer with a compact diesel tractor through a 150 mile trip so I'll have a better idea of how it feels under load. Ultimately I want it set up with the dual plane and any impressions with the stock intake are just for perspective.

I am running stock exhaust after the headers. I've looked at changing them but unlike OEM, the aftermarket stock replacement exhaust systems I've looked show no difference between 1/2 and 3/4 ton models. I have plans to get down to the exhaust shop and have a new system built front to back but that might not happen until August.

As to running a 305, no. The L31 is so common that I'd buy one used before installing the 305. I built the 302 years ago to do it, and because I thought it might be a good choice for an S10 Blazer. I've been dying to use it since and when I replaced the last Blazer with the Suburban, I found an opportunity to try it. If I were to build a long stroke, small bore engine I'd probably throw a 400 crank into a 350 block. IIRC that works out to about 338 cubes and it might make an interesting torqu engine with very good emissions.

400 crank into a 350 block is 377, 400 crank into a 305 is a 334 again depending on overbore.

I understand now why you chose a 302.

There are many after market replacements that differentiate between the 1/2 ton and 3/4 ton exhausts. Magnaflow, Walker and Catco are just 3.

Magnaflow 1/2 ton Vortec L31 350
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/350cats-1.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/350cats-1.jpg.html)

Magnaflow 3/4 L31 front and back
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/maggieheadpipes.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/maggieheadpipes.jpg.html)
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/backmaggieheadpipe.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/backmaggieheadpipe.jpg.html)

http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/walkerfrontpipe.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/walkerfrontpipe.jpg.html)
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/walkerbackpipe.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/walkerbackpipe.jpg.html)


catco front and back for 3/4 ton L31
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/catcofront.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/catcofront.jpg.html)
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/walkerbackpipe.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/walkerbackpipe.jpg.html)

On my stock longblock L31, headers/mild 87 octane tune changing only the PE fuel multiplier and exhaust dropped 1/4 miles times just under a second. Felt like I dropped a 383 under the hood. And that was with the same stock intake you are using. When I went to its match dimensionally anyways wit the Merc intake, I noticed better over 4500rpm breathing with small torque increases off idle and at low rpm.


All else equal the small bore 305 should be MORE detonation resistant than the larger 4" bore. I might be tempted to work from an L30 calibration.

Good work on your build. It muist be nice to finally see some fruits of your labours.

peace
Hog

[1project2many]

There are many after market replacements that differentiate between the 1/2 ton and 3/4 ton exhausts. Magnaflow, Walker and Catco are just 3.
I'll look again at Walker. Maybe I just missed it. Local exhaust guy is Magnaflow dealer so maybe I can get a good price on an expensive brand.


All else equal the small bore 305 should be MORE detonation resistant than the larger 4" bore. I might be tempted to work from an L30 calibration.

I've never really investigated the 305's issues so I can't tell you why it's more likely to knock. It would seem like head design is the key. The L30 represented a great chance to fix any problems inherent in the older heads yet the tuning tables indicate there are still problems.

Main spark table, knock attack, and knock retard rate comparisons are below. Yes, there's a bit more spark advance on the bottom end but at the top it's a whole different picture. Not only is timing lower on the smaller bore, but GM is really quick to remove advance if knock occurs and slow to return it. This is typical of the 305 although it's less pronounced here than older engines.

[ony]

one of the main spark tables is off in 2 aereas by 20-23 degrezz in the upper part of the table.

[Hog]

one of the main spark tables is off in 2 aereas by 20-23 degrezz in the upper part of the table.
That is the actual spark timing table, its the differnce in timing between teh 2 calibrations he is comparing. If you notice, it states COMPARE ON.

This is a stock L30 timing table
0rpm 400rpm 800rpm 1200rpm 1600rpm 2200rpm 2600rpm 3000rpm 3400rpm 3800rpm 4200rpm--5600-6000rpm
20.0 20.0 20.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 26.0 15 kpa
20.0 20.0 20.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 26.020kpa
25.0 25.0 25.0 30.0 30.0 30.0 10.0 10.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 26.0 30kpa
25.0 25.0 30.0 35.0 35.0 35.0 10.0 10.0 30.0 30.0 30.0 29.0 27.0 27.0 27.0 27.0 35kpa
25.0 25.0 29.0 33.0 34.0 34.0 33.0 33.0 33.0 33.0 33.0 31.0 29.0 29.0 29.0 29.0
22.0 22.0 28.0 31.0 34.0 34.0 34.0 34.0 35.0 35.0 34.0 32.0 30.0 30.0 30.0 30.0
22.0 22.0 26.0 29.0 33.0 33.0 34.0 34.0 36.0 36.0 35.0 34.0 32.0 32.0 32.0 32.0
20.0 20.0 24.0 28.0 32.0 32.0 34.0 34.0 35.0 35.0 35.0 34.0 32.0 32.0 32.0 32.0
18.0 18.0 20.0 26.0 30.0 32.0 33.0 33.0 34.0 34.0 34.0 32.0 30.0 30.0 30.0 30.0
17.0 17.0 17.0 20.0 24.0 27.0 30.0 32.0 32.0 32.0 31.0 27.0 25.0 25.0 25.0 25.0
11.0 11.0 14.0 17.0 22.0 25.0 28.0 31.0 31.0 30.0 28.0 25.0 23.0 23.0 23.0 23.0
7.0 7.0 11.0 14.0 19.0 22.0 26.0 27.0 28.0 27.0 24.0 23.0 20.0 20.0 20.0 20.0
4.0 4.0 7.0 12.0 17.0 20.0 25.0 26.0 26.0 25.0 22.0 21.0 19.0 19.0 19.0 19.0
2.0 2.0 4.0 9.0 14.0 18.0 23.0 23.0 24.0 23.0 20.0 19.5 18.0 18.0 18.0 18.0
-1.0 -1.0 1.0 8.0 12.0 16.0 21.0 21.5 22.0 21.0 19.0 18.0 16.0 16.0 16.0 16.0
-3.0 -3.0 -2.0 5.0 10.0 14.0 19.0 19.5 19.5 19.0 18.0 17.0 15.0 15.0 15.0 15.0
-4.0 -4.0 -2.0 4.0 10.0 14.0 18.0 19.0 19.0 19.0 17.0 17.0 15.0 15.0 15.0 15.0 95kpa
-4.0 -4.0 -2.0 2.0 8.0 13.5 16.0 18.0 19.0 19.0 16.0 16.0 15.0 15.0 15.0 15.0 100kpa
-4.0 -4.0 -2.0 2.0 8.0 13.0 16.0 18.0 19.0 19.0 16.0 15.0 15.0 15.0 15.0 15.0 105kpa

Stock 4.3 265 L99
18.0 18.0 18.0 18.0 18.0 19.0 17.0 15.0 12.0 9.0 6.0 3.0 2.0 2.0 2.0 2.0 400 rpm
22.0 25.0 26.0 24.0 22.0 21.0 19.0 23.0 17.0 15.0 11.0 6.0 6.0 6.0 6.0 6.0 600 rpm
26.0 28.5 29.5 26.0 23.0 21.5 21.0 25.0 22.0 19.0 15.0 12.0 12.0 15.0 15.0 15.0 800
29.0 39.5 39.5 39.5 34.0 27.0 27.0 32.0 26.0 24.0 19.0 16.0 14.0 15.0 15.0 15.0 1000
31.0 33.0 32.5 36.0 34.0 33.0 30.0 34.0 30.0 27.0 20.0 19.0 14.0 15.0 15.0 15.0 1200
33.0 35.0 35.0 37.0 35.0 34.0 34.0 37.0 32.0 30.0 26.0 22.0 19.0 19.0 16.0 16.0 1400
35.0 38.0 38.0 38.0 37.0 35.5 36.0 40.0 36.0 33.0 30.0 26.0 24.0 20.0 19.0 19.0 1600
36.0 39.0 40.0 38.5 37.0 36.5 36.5 43.0 37.0 34.0 33.0 30.0 25.0 23.0 16.0 21.0 1800
37.0 40.0 39.5 36.5 34.5 33.5 37.0 43.0 40.0 36.0 34.0 32.0 29.0 25.0 24.0 23.0 2000
37.0 40.0 40.0 38.0 36.5 35.0 37.0 43.0 40.0 38.0 35.0 33.0 30.0 28.0 25.0 23.0 2200
35.0 40.0 40.0 40.0 40.0 40.0 40.0 44.0 40.0 37.0 36.0 35.0 32.0 30.0 27.0 24.0 2400
35.0 40.0 40.0 40.0 40.0 40.0 40.0 44.0 42.0 40.0 39.0 37.0 35.0 33.0 30.0 27.0 2800
35.0 40.0 40.0 40.0 40.0 40.0 40.0 45.0 43.0 42.0 40.0 37.0 36.0 35.0 32.0 30.0 3200
35.0 35.0 40.0 40.0 40.0 40.0 40.0 45.0 44.0 43.0 40.0 38.0 37.0 36.0 34.0 33.0 3600
40.0 40.0 40.0 40.0 40.0 40.0 40.0 45.0 44.0 43.0 41.0 38.0 37.0 36.0 35.0 34.0 4000
40.0 40.0 40.0 40.0 40.0 40.0 40.0 45.0 44.0 43.0 41.0 39.0 38.0 36.0 35.0 34.0 4500rpm
35.0 40.0 40.0 40.0 40.0 40.0 40.0 45.0 44.0 43.0 41.0 39.0 38.0 37.0 36.0 35.0 5000rpm
40.0 40.0 40.0 40.0 40.0 40.0 40.0 44.0 43.0 43.0 41.0 39.0 37.0 36.0 35.0 35.0 5500rpm
35.0 40.0 40.0 40.0 40.0 40.0 40.0 43.0 42.0 41.0 39.0 38.0 38.0 38.0 34.0 34.0 6000rpm
35.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 36.0 36.0 6500rpm
32.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 38.0 30.0 30.0 28.0 28.0 28.0 7000 rpm

Stock L31 350
20.0 23.0 23.0 25.0 26.0 27.0 28.0 29.0 29.0 29.0 29.0 29.0 29.0 29.0 29.0 29.0 15
20.0 23.0 23.0 25.0 27.0 28.0 29.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 20kpa
20.0 23.0 23.0 26.0 27.0 29.0 30.0 32.0 32.0 32.0 32.0 32.0 32.0 32.0 32.0 32.0 25kpa
20.0 23.0 23.0 26.0 28.0 30.0 32.0 34.0 34.0 34.0 34.0 34.0 34.0 34.0 34.0 34.0
20.0 23.0 23.0 27.0 29.0 32.0 34.0 36.0 35.0 35.0 35.0 34.0 34.0 34.0 34.0 34.0
20.0 23.0 23.0 28.0 32.0 34.0 36.0 36.0 36.0 36.0 35.0 34.0 34.0 34.0 34.0 34.0
20.0 21.0 23.0 28.0 32.0 34.0 35.0 36.0 36.0 36.0 35.0 34.0 34.0 34.0 34.0 34.0
18.0 18.0 21.0 28.0 32.0 33.0 34.0 35.0 36.0 36.0 35.0 34.0 34.0 34.0 34.0 34.0
14.0 14.0 19.0 26.0 30.0 32.0 33.5 34.5 35.0 35.0 34.0 33.0 33.0 33.0 33.0 33.0
12.0 12.0 16.0 24.0 28.0 31.0 33.0 34.0 34.0 34.0 33.0 32.0 32.0 32.0 32.0 32.0
11.0 11.0 14.0 21.0 26.0 29.0 31.0 32.5 33.0 33.0 33.0 32.0 31.0 31.0 31.0 31.0
9.0 9.0 11.0 18.0 23.0 27.0 29.0 31.0 32.0 32.0 32.0 31.0 30.0 30.0 30.0 30.0
7.0 7.0 9.0 15.0 20.0 25.0 28.0 30.0 31.5 31.5 30.0 29.5 28.0 28.0 28.0 28.0
5.0 5.0 7.0 13.0 17.0 23.0 27.0 29.0 29.0 29.0 28.0 28.0 26.0 26.0 26.0 26.0
2.0 2.0 5.0 11.0 15.5 21.5 25.0 27.0 27.0 26.0 25.0 25.0 24.5 24.5 24.5 24.5
0.0 0.0 2.0 8.0 14.0 20.0 23.0 25.0 25.0 24.0 23.0 23.0 23.0 23.0 23.0 23.0
-1.0 -1.0 0.0 6.5 12.0 18.0 22.0 24.0 24.0 23.0 22.0 22.0 22.0 22.0 22.0 22.0
-2.0 -2.0 -1.0 5.0 11.0 16.0 20.0 22.0 22.0 21.0 20.0 20.0 20.0 20.0 20.0 20.0 100kpa
-2.0 -2.0 -1.0 4.0 10.0 15.0 19.0 21.0 21.0 20.0 19.0 19.0 19.0 19.0 19.0 19.0 105kpa

[ony]

at 25-30 kpa -2400-2800 it shows a lot different than the rest of the table, could make for knocks in them cells.

[1project2many]

at 25-30 kpa -2400-2800 it shows a lot different than the rest of the table, could make for knocks in them cells.

It's not so uncommon to see GM throw a bunch of advance at an engine after a certain MAP and RPM. But the telltale is that spark advance begins to drop rapidly as rpm increases. For the L30 GM pulls 4-5 degrees along a given MAP range as RPM increases while the L31 sees only a degree or two at most.

What's even more interesting for comparison is the L99 table. Same bore as L30 but with shorter stroke, longer rod, and reverse flow cooling there's an additional 10 degrees advance at WOT.

The 305 just seems to have issues with advance.

[Fast355]

It's not so uncommon to see GM throw a bunch of advance at an engine after a certain MAP and RPM. But the telltale is that spark advance begins to drop rapidly as rpm increases. For the L30 GM pulls 4-5 degrees along a given MAP range as RPM increases while the L31 sees only a degree or two at most.

What's even more interesting for comparison is the L99 table. Same bore as L30 but with shorter stroke, longer rod, and reverse flow cooling there's an additional 10 degrees advance at WOT.

The 305 just seems to have issues with advance.

Not sure where you are getting all that WRONG SA info on a 305. Keep in mind the L99 was in a car that is lighter and more aerodynamic than the trucks and vans the L30 was put into. The mechanical engine fan alone tends to make the engines more SA sensitive in hot weather as it puts a heavy load on the engine in hot weather. The L99 also has longer rods and a better rod/stroke ratio that makes it less sensitive to detonation under heavy load.

The 305 is not spark advance sensitive, just does not need as much advance as a 350 with its smaller bore the flame front travels more quickly across its smaller area. If anything the 305 is more detonation resistive than the 350. I ran 10.8:1 compression and 230 psi static compression with the old iron 601' casting 305 heads on 93 octane pump gas with a carb and ran 34* total advance doing it.

[1project2many]

Not sure where you are getting all that WRONG SA info on a 305.
The table I've posted is a comparison of stock tables taken directly from GM calibrations. Why do you say it's wrong?


The 305 is not spark advance sensitive, just does not need as much advance as a 350 with its smaller bore the flame front travels more quickly across its smaller area.
Based on experience and backed by what I've seen come out of GM engineering, I disagree fully with your statement. I've been working on 305 equipped vehicles since the '70s. Stock 305's have always had a greater tendency for spark knock. In the '80s, the only GM truck to receive knock control without a fully computerized ignition system was 305 equipped. That wasn't just an experiment to see if it would work. I know what happens when you disable or remove that system. Look through cals matching year for year, 350 to 305, you'll see consistent indications in the form of more aggressive knock retard, less aggressive restore rates, and timing tables that favor less advance on top end. It is not because the 305 needs less advance to create peak pressure at the same time as the 350. Based on the number of degrees difference, the amount of time involved is too great.


Keep in mind the L99 was in a car that is lighter and more aerodynamic than the trucks and vans the L30 was put into. The mechanical engine fan alone tends to make the engines more SA sensitive in hot weather as it puts a heavy load on the engine in hot weather. The L99 also has longer rods and a better rod/stroke ratio that makes it less sensitive to detonation under heavy load.
I am fully aware of the stock configuration of the L99. Which is why I said the stock spark tables make an interesting comparison. And while I agree that a mechanical fan puts more load on an engine, I think it would be naive to say this factor is more important in the L99 timing tables than reverse flow cooling. Cooler heads inhibit combustion rates and the reverse flow engines run substantially cooler heads than standard flow engines.


If anything the 305 is more detonation resistive than the 350. I ran 10.8:1 compression and 230 psi static compression with the old iron 601' casting 305 heads on 93 octane pump gas with a carb and ran 34* total advance doing it.

I have experience tuning. Personally I built and ran a 10.8:1 350 on 87 octane fuel with a manual transmission and a tunnel ram style marine intake on iron heads. That engine was in the 400 horse range. I own a Pontiac Turbo Sunbird 2.0 running 17 psi boost on the stock turbo and fuel system and it hasn't launched the headgasket. That's a tough feat to accomplish with that engine even with upgraded parts. Mine's tuned for 89 octane and I've got a *lot* of time into the cal. I ran a 2.2L engine with 9.4:1 and nearly 8 lbs boost. The engine is stock with the addition of a very small turbo and no intercooling. It was a huge challenge to tune between the wide range of intake temps and the way too large TBI injectors in the PFI intake but the point was to prove it could be done. It made fair power, and the engine didn't blow up as many had predicted. And to make it fun I kept it on 87 octane. I pulled the engine, still running, when I sent the car to the junkyard for rust and saved it for future use. I also have a 302 powered '57 Chevy pickup with Crossfire injection. First installed in '92, I used a 305 ecm from an '83 Firebird. I moved on to a 7747 in '99, and now use a 7427. I have retuned it with each ecm change and have plenty of hours working with the spark tables in that engine as well. For perspective, that engine uses 601 castings and 1.84" valves.

Are you emotionally invested in defending the 305? I'm not discussing (or dissing) it's worth as a potential powerplant. Hog suggested using stock 305 spark tables as a starting point for my 302. I do not believe those tables are the best starting point and I've indicated why.

[1project2many]

Well, the truck made the trip successfully. I'm guessing I was pulling about 4k lbs between the tractor, trailer, and a bunch of "stuff" I pulled out of an old garage. I know that's not a large load but it's probably typical of what I'll be hauling. Overall I'm satisfied that this truck will work out although if I was crossing the Rockies or maybe even towing on the high plains the current combination probably wouldn't make me happy.

There were a couple of larger hills on this trip and at least twice I spent a significant time at WOT on the way home. Dyno software predicted the engine would feel flat around 2500 with the stock intake and boy, does it. At 65 mph I'm right in the middle of that flat spot. The combination of 3.42 gears with the current intake keeps the trans busy which means I've got more work to do nailing the shift tables. I'm going to see if there's a tow/haul or economy switch that will fit right into the dash to make use of dual shift patterns. 3.73 gears would be nice but I'm not likely to go that far. I was towing the entire trip of 335 miles which meant no OD. Empty trailer one way, loaded trailer the other, lots of hills in the middle so I was surprised to see 12 mpg when I calculated the fuel economy. Not that it's engine related, but I'm going to be replacing the gear oil with full synthetic. The diff gets warm when towing and the airflow around the truck carries the smell of hot gear oil right into the passenger area.

So subsequent work will be:
install large trans cooler (didn't have time to install during engine adventures)
service differential with synthetic fluid
Tow / haul button
Adjust shift tables for faster TCC unlock and quicker downshifts, and to hold downshift longer
hot restart parameters still need adjustment
-->Fix A/C!!!<---

[EagleMark]

-->Fix A/C!!!<--- Yup! :thumbsup:

[Hog]

Glad you made your trip, I really wish I could take a 302 for a spin just compare the powerband.Thats weird about the 505 being less detonation resistant. All else equal, a smaller bore should exibit more detonation resistance. Every chart I have ever seen says that higher coolant temp, larger bore, lower fuel octane will be less detonation resistant than lower coolant temps, smaller bores and higher octane gasolines. I have no experience of my own that compares the 2 bore sizes. I am interested in doing a short stroke engine, the L99 crank is interesting. Take care.