Quote:
Originally Posted by Dragncar
The part I am wondering about is where he takes the total potential HP on a 338 cfm head and uses the 91% of the exhaust flow and only comes up with 639 horsepower. (703 x 91%)
No Pontiac head I know of has a 91% intake/exhaust ratio so the typical Pontiac head is going to be worse.
But we have all seen 340 cfm Pontiac heads making far more than 640 horsepower.
Am I missing something ?
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I was thinking the same thing because the ratio between intake and exhaust flow on a Pontiac engine is not great even on a ported E-head with upgraded 1.77 exhaust valves, yet they still make pretty good power so I would say the data he provided in the video was flawed or at least exaggerated with regards to HP limitations on exhaust to intake flow percentage. Even so I didn't agree with everything presented in the video but still think some good info was presented and it was an interesting presentation on both videos. It appears most of his experience was related to LS, SBC and BBC engines. He also discussed the long debated short rod long rod subject. Smokey Yunick said to install the longest rod that can fit into the engine, what he didn't say the longer rod will give you more power. Pro Stock cars don't have an ideal rod to stroke ratio but make massive power per C.I. So I believe the real advantage to a long rod is reduced cylinder wall loading which will give some longevity to the bore and less stress on the rotating assembly. Some say cam selection is critical to a long rod vs a short rod engine because a longer rod will have he piston dwell longer at TDC than a short rod. There is a tradeoff at some point as a short rod weighs less and a long rod has less cylinder wall loading. For a bracket car a longer rod is my preference.