[John R]

Originally Posted by Bored&Stroked

Actually, you were not wrong - it is all about the application and usage of the engine. Relieving a Ford Flathead does nothing of value before about 4000 - 4500 RPM . . . actually it hurts low end power as it reduced compression (with everything else the same). Also, relieving is just one small piece of the overall puzzle - you have the ports to worry about (they take serious amounts of work), you have the cam to worry about, you have the valves, the chambers in the heads, etc.. As Pete noted - when all the things are specifically designed to work together (for racing) - then relieving is part of the "combo" that was typically used.

Also, typically these naturally aspirated engines were fuel injected - which surely adds horsepower over the typical Stromberg setup. And truth be told, the classical Hilborn flathead injector is too small for max HP. Guys like Don Ferguson Sr. cast their own injectors way back in the 80's - with big port/butterfly sizes more like a SBC injector (to get the flow they needed).

Then, one can start talking about oil-control, dry-sumps, crank scrapers, vacuum pumps, low-tension rings, straight-cut cam gears, etc.. A lot can go into one of these engines - and it is not for those "on the cheap".

Dale, Thanks for a very balanced and informative discussion of the topic!.
John