[Steve C.]

For interest, and related to the intake runner volume ? And the RPM involved.

The larger stroke engine will be sensitive to under-flowing heads. To illustrate, grab a bicycle tire pump some time, and first try to operate it as quickly as you can. Then, slow down the pumping action. You will notice that it is far easier to move the pump handle slowly. Your engine is no different- slow down the piston, and the engine has less work to do. Again, this situation is aggravated by high RPM conditions. The important thing to remember is that no matter how fast or slow the piston goes, the engine moves exactly the same amount of gasses during the same number of crank degrees. This situation could be improved by using the longest rods possible, which would increase the rod ratio and somewhat alleviate the angularity problem.
by Phil Parsons


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