To check how much power I loose when going to 297 instead of the 385 cc I flowed the heads of the 250 and the 385. The under pressure used for themeasurement is 18 inch of water. As can be seen on the graph the 250 is about 10 grams less than the 385 so I estimate that this will cost me 6 to 7 horsepower. Maybe this can be limited to less if I can find some grams of air in the 250 head by some reshaping of the inlet track.
Below the head of the 250 on the flowbench.
The camshaft of the 250 and 385 have an identical profile given in the drawing below.
