Quote:
Originally Posted by dantm
Thanks guys, the leakdown we were measuring was in excess of 70% on two (out of 12) cylinders.
I'm thinking with the tolerances we just measured a gap of 0.007" in a 3.2" diameter piston is just too large (gap should be 0.001" per inch of diameter so about 0.003" max tolerance between piston and cylinder). I wonder if due to that the rings were just not seated right and we got the numbers we did?
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a piston/cylinder gap being over a couple thou will not give a 70% leak down.
a burnt valve or broken ring or huge ring gap will give a 70% leak down
make sure you are doing the test correctly, testing on TDC on the exaust stroke will give bad readings if there is some overlap with the valves (valves will be slightly open)
I test heads by installing the valves and plugs and filling the chamber with water or gasoline and looking for leaks in the ports