Quote:
Originally Posted by otto_kretschmer
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
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Thanks -- we took out the cams so all the valves are fully seated and the TDC question is taken out of the equation.
In the next test we are making a flat plate that will seal on each cylinder and allow the pressure test in the chamber (and separately the plate can be mounted on the heads to test each pair of intake/exhaust valve).
With regards to the 70% leakage the issue was that we were seeing it on 2 out of 12 cylinders, with the others at very low numbers (sub 10%?) with engine cold and a fresh rebuild. But the heads, gasket, were not taken out of the equation. The heads had been tested separately by having them upside down and filling the heads with gas to check for any leaks.
Thoughts?
Thank you!