How much power am I leaving on the table running 243 heads vs some other heads? On a 421" motor in a jet boat. Thanks.

 

Are they ported? If not there is some to be gained with a good port job. But with a motor that size you might be better off with some good aftermarket heads like Trick Flow or Airflow Research. Their heads BREATHE. Which cam do you have? Intake manifold?

 

243 heads are what ? 260-270 cfm

LS3 heads are 315 cfm

40-50cfm = 80+ HP "capable"

Roughly 2 - 2.2 HP per cfm

 

The question gets down to peak torque and where it occurs. I need the peak torque to be pretty high in the rpm range and as high a number as possible. More important to me than peak hp since I'm not likely to spin enough rpm to hit peak hp.

 

243 are:
Combustion chamber 64.45cc
Intake port : 210cc
Exhaust Port 75cc.
At 600 lift they flow 278 cfm all things being correct.