So if I had an 89 IROC with an LB9 and had a good longblock L98 to swap in, is there anything different between the two other than the cubic inches? Does everything bolt up? Manifold, motor mounts, transmission, serpentine, etc?

If I had a choice between various L98 longblocks, which are the best ones for horsepower? The Vette ones?

 

I believe they would be the same externally. 305 heads are different than 350 but accessories should still be same

later year L98’s are said to get flat top pistons which give more compression but got slightly smaller cam in duration. My L98 had a slight dish piston

 

Thanks. That helps. I was going to swap the cam anyway with the GM 94666492. Is there a way to tell which L98 it is from casting numbers?

Thinking this one:

https://www.ebay.com/itm/202016148002?ul_noapp=true

 

I prefer this one.


https://www.ebay.com/itm/GM-Chevrole...t/253708804971

 

Tootie, the one you linked is a flat tappet engine, swapping to a roller cam would be expensive.

 

Ah. Ok. So I want to look for a roller. I might scour a few machine shops around here to see what they have. I'm trying to avoid getting into compression ratios and all that stuff- go with a used long block with a higher compression ratio, good flowing heads, and a roller?

I'm thinking since I'm really after cheap horsepower engines out of specific cars are probably my best bet like later C4 vette motors? or even an L31?

 

TPI itself is IDENTICAL IN EVERY WAY between the LB9 and L98. Same TB, same plenum, same runners, same base, same fuel rails, same same same same.

Things that are different are, 85-86 F body and all Vettes, use the old style intake bolt angle. 87-up F body use the later angle where the center 2 bolts on each side are more nearly vertical. Vettes use an external EGR plumbing setup because the heads don't have the center exhaust passage.

Other than that, different size injectors (19 lb/hr vs 22, measured according to the Rochester method which is different from most others); knock sensor; ESC module in some years.

And, there are a few year model differences, not related to 305 vs 350; MAF vs S/D, and presence/absence of the cold start injector, for example.

 

Thanks. That sums it up. Easy swap to pick up a few cubic inches.

So if I picked up a later Vette roller I would need to source and external EGR setup from it as well. Which means different exhaust manifold(s) and perhaps a different intake manifold/EGR valve. Would this mean that the stock Y-pipe would no longer match up to the Vette exhaust manifold with the external EGR?

 

Vette manifolds won’t work . They are center dump.

 

Welcome to the 3rd Gen world of custom. Alot of choices, but you're in the right place!

 

If you come across a early 90s Cadillac, Roadmaster, even a few Caprices have a roller L05 350 engine. They have crappy heads but sometimes you get these engines cheap. You can find heads for it on E-bay cheap also.

 

If you get a vette L98 just use your 305 tpi manifold and delete egr. Oval the holes for intake bolts as needed. Else if you need egr then you will need vette system which takes egr off the header/exhaust manifold and not the heads

or throw your 305 heads on and keep the 305 tpi but then that defeats the advantage of the vette L98, the aluminum heads which saves 50 lbs

 

Can't really "just delete" the EGR in CA.

Bolting a base w the valve on it to heads that don't have the passage, might fly however. As long as it's not one of those valves with the temp sensor which a code will set if it doesn't get exh heat, and they don't notice the heads, and the NOx emissions (the ones EGR holds down) pass, … no guarantees of any of that though.

 

Man, the more I read the more I think that if going to bother with cheap-n-easy swapping in a 350, I should be able to use an L31/Vortec with only the EGR and intake (Scoogy Dikeys? whatevs) to fuss with. The rest bolts right up and apparently the heads flow much better. I will want it to pass smog. but visual is not an issue so I can rig up a functioning TPI EGR I think. Hmmmm. Aaaargggghh.... wrestle wrestle toss turn wake up screaming at the ceiling at 2AM. Wife pissed.