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December 3 2017 at 10:04 AM

Blair Patrick  (Login CaptCobrajet)

Response to Blair, can you tell me the approximate peak hp of these three engines?

For the sake of round numbers....670-650-610....TW, 2x4, RPM, respectively. All were 11:1, with BBM heads with my hand porting. All three pairs of heads were prepped identically. Both dual carb intakes started taking "nibbles" against the RPM intake as they went through the range. What those peak numbers don't tell you is that below 4000 rpm, the dual plane 2x4 killed the TW, and the ED RPM killed both. I have since tried the RPM with the bigger cam, and it didn't show me much difference. I think, as a larger displacement engine becomes "cylinder head limited", a big cam only removes torque and won't do much for peak power, especially if it is a long stroker. The more data I collect on different engines with the same heads, it is evident that the bore/stroke relationship has more effect on things than just having more or less inches. How you arrive at those " inches" makes a difference. Combo is everything.

Back before the stroker world came along, we could see the difference in rpm ranges between 3.78 and 3.98 strokes in the Stock and Super Stock stuff. When head cross-section is close, the 3.98 always makes more torque a few hundred rpm sooner, and the 3.78 always makes it's peak power 2-300 after the 3.98. I once built a 3.78 stroke engine that made a little over 900 ho at 8000 rpm, and then did an identical top-end on a 4.400 stroke that made the same power, but at 6600 rpm. Needless to say, the big engine had a boat load more torque. I may be rambling now, so I'll shut up. Not sure how I got off track talking about stroke....oh yeah......point being.....combo is everything.
Blair Patrick

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