[Bernie Cunningham]

Originally Posted by Bill Harris

Larry, it is interesting that you used the GM engine as an example of current high tech in as much as it is one of the lowest tech modern engine designs. It is somewhat amazing that GM is able to get such high HP to CID numbers from a production engine that still has an archaic pushrod/rocker arm design operating only 2 valves per cylinder in an in-line wedge chamber. Think of all the time and energy that has gone into pushrod engine design; hemi, semi-hemi, canted valve, splayed valve, twisted wedge, ad nausem, and then see that the most modern hi-po GM engine has the same geometry as the 1955 265. Yeah, there are all the latest tricks like electronics galore, variable valve timing, direct injection, exotic materials, optimized flow and CNC machining. But, in reality, the latest Corvette LT4 isn't terribly far from the original SBC (or SBF, or small block Chrysler, AMC etc, etc.)
Contrast that design with nearly any foreign engine from Japan, Germany or Italy, and more lately with the Ford Modular engine family and the GM stuff looks very dated in it's basic design. When do you suppose a pushrod engine last came out of any of the foreign companies? I think that even Honda lawnmowers have an overhead cam.
All that being said, it is surprising at how far GM has been able to bring that basic design and keep pace with the more "advanced" designs. There must be an economic reason to stick with the single cam inline wedge design, and it sure has to be more popular with the aftermarket crowd. I always wondered how expensive it must be to try a new cam profile on a Cobra Jet engine. It is bad enough buying one camshaft let alone four. But think of the money you save in valve springs!

Good one, Bill !