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Originally Posted by rcair3d  From what I have been told you want very little pressure, if there is a good flow the valves are not seating right or are worn. I was more or less just curious. I have had three of these motors and all had a surprising blow-by. |
That is normal. You don't want a smoke-stack out of that oil cap hole but a fair amount comes out of there. As the pistons move up and down in their bores they create positive and negative crankcase pressures which will blow-through the oil cap if it is off. You will see the crankcase gasses escape from the oil caps' hole but won't see the quick periods of lack of pressure or almost negative pressure.. Remember all piston rings in perfect condition have a gap that allows 2%-3% on the compression stroke blow-by, imagine the percent of blow-by when that pistons compressed charge is ignited and those rings take thousands of more psi then a simple 100psi from the leak-down tester...
John Smith