SPANKY LS1

iTrader: (24)

Does 10% increase in CI= 10% increase in HP/TQ? If a 346 motor produced 450rwhp, if you added 34.6 cubic inches (10%), would the motor produce 10% more HP/TQ? If so, when do "diminishing returns" occur?

Does 20% more CI= 20% more HP/TQ?
Does 30% more CI= 30% more HP/TQ?
Does 40% more CI= 40% more HP/TQ?

Old SStroker

It could if it could pump the additional air at the same efficiency. That usually means better flowing intake and exhaust system, and perhaps different cam timing. So just increasing displacement 10% with no other mods would probably result in less than 10% increase in torque and hp. With 450 on a 346 LS1 you already got 10% or 20% or more torque and hp just by significant airflow changes (H + C and the required exhaust mods).

Diminishing returns on displacement/power probably occurs when you can't get enough valve area for the required airflow because you are limited by bore diameter. In other words, the architecture of the engine is the effective limiting factor.

40% increase of displacement on a 346 would be 484. It's probably not very practical to go that big on the LS1 architecture. On the other hand, a BBC can easily get there, and with available heads it would probably produce more torque and power than a 484 LS1, and for a lot less money.

A BBC with 4.5 bore and 3.8 stroke is a 484. If you could get a 4.15 bore in an LS1, you'd need a 4.47 inch stroke to get 484. No way you are going to get 2.25 intake valves in that bore like you can in the 484 BBC. The 4.47 stroke will also limit max practical rpm to 6500 or so where the 3.8 stroke engine could go to 7700 with the same average piston speed.

My $.02