Dr. Jeckel

iTrader: (12)

Did some reading but really couldn't find good numbers. Anyone know what the difference would be between a forged 347 and forged 383, everything else being the same?
For example: My setup with TSP 5.3L stage 2.5 heads, what kinda difference could be expected?

Thanks, James.

slow trap

iTrader: (22)

i would think 40 ftlbs or more,especially in the lower part of the powerband.

Steve Bryant

iTrader: (1)

If you transferred your heads, intake manifold, throttle body, cam and headders to the 383, your torque would go up by about 7% and the torque peak would occur at about 200 RPM's lower. Your peak HP might go down a few percent and the RPM of peak would be lower. That's my two cents.

Steve

Dr. Jeckel

iTrader: (12)

So your saying that with heads and everything else that my torque would go from around 400 to only 428 ...that seems quite low compared to what I have read.

Sigforty

That sounds about right to me. You need to think that when you increase the cubes the engine requires more. The same cam in a 346 will be smaller in the 383 because the engine moves more air and needs more. The heads, headers, intake, and cam all play into the entire package. You need to optimize everything for each setup as they are two different animals.

slow trap

iTrader: (22)

i don't know about the percentage thing.that might be the case if your heads were maxed and you couldn't keep up with more cubes but almost always nobody has their setup maxed. all the extra cubes is coming from a longer stroke.usually a decent setup makes close to it's cubes in tq at 3k so if a 346 makes 346 rwtq @3000 then a proper 383 should make 383 rwtq @3k which would be 37 more ftlbs.of course as always there is variables but a decent head like the prc 2.5 should be able to feed a 383 and make such power.

Dr. Jeckel

iTrader: (12)

https://ls1tech.com/forums/showthrea...&highlight=383
Judging by this thread I should be looking at approximately 40rwtq increase, with similar horsepower. Nice call slowtrap

john563

iTrader: (17)

Im really glad that you started this thread cuz i plan on stroking mine to 383 this time next year and i have the same heads i would just need alarger cam. So guys keep em coming woul like to hear more opinions