Thanks for the softball question.....

Ground Rules: This is a rule of thumb question and will get a rule of thumb answer.

The number is actually a little bit more than 2 hp / cubic inch, but it applies to head flow. The size of the engine determines what rpm this peak power will need. So let's pretend the number is 2.000.

With a 200cfm head on a 400 cubic inch v8, suppose peak power was at 400hp at 4000 rpm. Put that same set of heads on a 300 cubic inch v8 and peak power becomes 400hp at 5333rpm.

Back in the day, I spent Christmas vacation in the ME Library at my University. They had a complete set of Journals of the SAE. What a treasure chest. I read papers by men like Fred Duesenberg with power curves of the same engine with a two valve head and with his four valve head. I read papers on the development of the Dynaflow, which was basically the beginning of torque converters. And from the '50s I read papers from the pioneers of the hot rod industry. The paper that changed my thinking was on flathead Fords. The author had built an engine in three different displacements and posted dyno curves for each configuration. The max power for each size engine was exactly the same. The curves were just arranged from largest engine to smallest engine, along the rpm scale. Displacement only shifted the power curve right or left, it didn't change the amount.

R.