From my understanding the early Merlin engines had 43 degrees of valve overlap. This the period of the rotation of the camshaft at the end of the exhaust stroke and at the beginning of the induction stroke when both the inlet and outlet valves of the combustion chamber are open. It allows the cylnder to fill as completely full of fuel air mix as possible before the combustion cycle continues.
This allows the engine to produce more power at high RPM. Unfortunately the flip side of the equation is that she idles like a dog and run rough at low speeds.
Later Merlins like the 70 series, had overlaps increased to about 70 degrees. They will really run rough at low revs.
Last edited by Skoshi Tiger; 05-09-2012 at 11:25 AM.
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05-09-2012, 11:02 AM
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