Tom, thanks for the link. I thought these excerpts were noteworthy:
"At 5.4L,
the GT minimum power requirement of 96 HP/L significantly exceeds the 4.6L application specific output of 85 HP/L. This increased demand on engine subsystems led to significant upgrades for the GT engine. The cylinder block would have to be
strengthened, coolant flow increased, and
oil flow increased to support piston cooling."
and
"Cylinder head combustion sealing would require refinements for increased cylinder pressures. It would also require improved exhaust valve cooling and added clearance for high lift cams."
and
"the resultant stress on the piston mandates cooling."
I beg to differ with Roush on the "would have to be" point(s). I am at ~137 HP/L on a non-GT block with stock cooling and oiling systems. But then, I have a truck radiator!
Fun aside, I do not flog the motor for long periods and I'm sure Ford will have fewer long-term failures with what they and Roush have done, though. And you can probably beat the heck out of it on the road course for extended periods. Another SAE paper, 2004-01-1257, specifically talks about this subject (cooling, mostly).
Something interesting in that other SAE paper: Combustion airflow is listed at 61 lb/min. Hmm!
Chris Weisberg
Carroll Shelby Enterprises
(310) 538-2914