Most L98 rebuilds here seem to go for the 383 ci displacement. I was reviewing Dick Gulstrands GS80 build and they decided for those cars to go with 372. Haven't gotten a response why back from them, but since they were putting down serious HP do you think 372 ci is for durability reasons?

 

383 is popular because it only involves a crank swap if doing a full engine rebuild using relatively cheap off the shelf items

Gulstrand used cubic $$$
Traco Engineering began with a Chevrolet HD Bow Tie block, bored to 4.125 inches. A 3.48-stroke, forged-steel GM crank; Carrillo rods; and JE pistons brought displacement to the prescribed 372 cubes.The heads underwent some 50 hours of shop work .

Dyno testing of the 372ci engine yielded 365 hp and 430 lb-ft torque

Easily make that with a basic 383 these days

Take into account building a 383 in '85 was a lot of hard work ; no off the shelf items available;
had to modify a 400 crank to fit in 350 block so 372 was probably a viable option back then
given the short stroke/ big bore combos ability to rev

 

What are your goals for your car?

 

My motor has 123K on it. I autocross so the main strain on the engine is prolonged redline in 2nd gear. I am doing my homework in the event I have to do a rebuild. Running last year I saw 3 engines blow, and 2 transmissions take a dump. I lost a clutch.

The biggest issue for me is California smog compliance. My rebuild will likely feature the stock heads port matched, with the valves unshrouded. Externally the only change I am likely to make are the runners and I am not sure if I would go SLP or Edelbrock. I have not been able to find a set of CARB compliant headers.

Perhaps I missed it, on the 383 arent the cylinder bores increased as well as the crank and rods being changed to increase displacement?

Thanks

Art

 

Only as a matter of "maintenace". A 383 is a .030" overbore on a 4" bore, combined with the 400's 3.75" stroke. A stock 350/4" bore and 3.75" stroke would give you 377 CID.

The Guldstrand motor was basically a SBC400 w/a 350 crank. I can't imagine how or why that would have been better than using yerbasic 400. More cubes = more power and tq.

 

Art, the Accel runners look stock and pass ca smog insp far as I know. Same with the base. Do some "work" on those, stroke the motor and noone will know the better. You can use a few different sized rods for the 383 most use 5.7, some 5.85 some 6 depending on piston selection.

If youre stuck with stock heads is it for a class racing thing? Youll need more than port matching to make power, stock they will choke a 383.

Putting larger valves and port work can wake them up but its less # to get a smog legal set of aftermarket heads that will blow them away.

Smog sniffer cant spot cubic inches. Cam, tuning come into play, you could do a 400+ci in engine and pass...there is also the superram if you can find one which is smog legal.
Problem is longtube headers....

 

I've been a fan of this build for a long time for someone that wants to retain much of the factory look, emmissions and reuse some of the existing motor.

If your goals are similar to the ones he laid out, it may may be a good starting point. (see nav bar on the left of his page for pg2 of the build)

Recipe for 400hp L98

A question for the engine guys, do you think it's worth going 383 if someone wants/needs to retain a factory style TPI? (Possible future plans of an intake replacement excluded) "There's no replacement for displacement" vs "The law of diminishing returns" ???

Any comments on Joe's build? Something you might do different within the parameters/budget? Results were 326/399 to the rear wheels, certainly not much by todays (non-TPI) standard but seem pretty good for what he did.

 

I'd do it. And, this is the one situation where I'd be tempted to siamese the stock base. The increase to a 383 would insure no torque loss while the siamesed base would suck air from 2 vs 1 stock runner tube.

Good point. FWIW: For Grantar's application (high rpm), the 6" rods get you more power. Plus, they take more advantage of cam overlap which makes overlap appear bigger. Had I not found a smokin' deal on Wiseco pistons, I would have picked the SRP (lightweight 4032) pistons with 6" rods. If I raced, I would have done it anyway. This option can get up 10-20 more hp.

The rod length actually affects how fast the piston moves in certain parts of it's travel. That's why there's a difference. Shorter gets more low-end performance, longer rods provide more high-rpm power.

 

The stock head are basically about keeping the stock part numbers on it for the smog guys in California. I have a machine shop that does custom CNC that will do the job for me very reasonably. We race together, old hot rodder turned autocross. The intent was to enlarge the valves, as well as unshroud them.

I'll look more closely at the Accel, was looking at the Edelbrocks because they are CARB legal from the manufacture. SLP's because Corvette Plenum seems to do a nice job modding them, although I have found anyone that uses either his ported plenumn or runners.

 

Why limit yourself to a 383? I'm going 396. More torque and horsepower. My 396 is being built now. The only significant difference from a 383 is the need for higher quality rods. I'm using Crower Stroker Sportsman rods that require less clearancing of the block and allow use of a standard base circle cam. With a Super Ram and AFR 195 heads, I'm looking at 500 Hp and over 500 Ft lbs torque. And by the way, this will be a California emissions engine. A very streetable sleeper.

 

You don't need stock heads to pass smog. AFR heads are Calif legal and far better. So is the Super Ram. I have copies of the EOs to prove it. I passed smog with both no problem. I just happen to have a set of AFR 195s for sale if you're interested. They have less than 5,000 miles on them.

 

FYI Oliver billets will clear a std base circle cam with a 4" stroke...

 

My bad, not sure what "std base circle cam" is refering to?

 

Olivers are definitely high quality and also feature 7/16 bolts. They're just more costly.

 

Longer stroke rods can interfere with the cam. The interference occurs on the upper part of the large end of the rod. You can get smaller diameter cams that eliminate the interference but they typically need to be special ordered for a special price. It's nice to use off-the-shelf parts whenever possible.

 

The cost comment was referenced to doing a full rebuild on a 350 ( out to 355 ) where you have to bore cylinders and fit OS pistons anyway
No need to change rods with stroker engine

 

Sonny Lenoard has a 500 cu. in. small block not to mention his 940 cu. in. big block I'm sure they aren't smog legal Pipe

 

You have to understand that TRACO Engineering was primarily an oval track and road racing engine company. Their experience was with sustained high RPM endurance engine building. It was what they knew best and that is why they used the big bore short stroke combination for Gulstrand... Look at the parts list they used in that engine.... Affordable is not what comes to my mind. A GM bowtie block is a racing piece and cost about $1800 unmachined. A set of Carrillo rods will set you back over $1000 today. Shelf stocking JE pistons retail in $650 range... Some companies still use those 3 same name brand parts in top tier racing engine to this day.

Joe Sherman first figured out how to make the "affordable" common 383 we know today by modifying the 400's cast 3.75 stroke crankshaft for use in a 350 block. It's been a really popular combination ever since because of the affordability.

Even as the Hp increased to the point where stock 400 cranks wouldn't hold together and the aftermarket started mfgring 3.75 stroke cranks - the price stayed low becasue they knew they could sell a bunch of them. Price and selection of parts for the performance increase is why so many folks build a common 383 today.

With the level of quality in some well selected aftermarket parts a common 383 will easily withstand being hung out in 2nd gear for auto crossing and easily match or exceed the power outputs of those old TRACO engines.
Will

 

I vote 355. I regret going 383 for racing, it was an unnecessary cost to an already expensive build. Yes, I have brilliant performance and reliability, but I got very little HP and about 40 ft*lbs jumping from the stock 350 block to the 383 (same exact top end). Yes, 40 ftlbs is 40 ft lbs, but I had enough power without it...

I did it because "I was already in there", and it added probably $2k in engine work and parts. More is not always better.

 

I decided on 355 for mine. Partly to fit in the race class I wanted and partly for cost. The power it's making is great all the way up to 6k. With the lower initial cost I also got it back on the road very quickly. Search my threads for build info.

Corkvette made a pretty cool thread on his displacement findings awhile back:

http://forums.corvetteforum.com/c4-t...r-thought.html