Compression pressures

[Stuart Giles]

You can do a useful test to get an idea of where the compression is being lost. After doing the compression test in the usual way with the throttle fully open, shoot a squirt of engine oil down each plug hole onto the bore walls; the cold oil provides a temporary seal. So, if the compressions are markedly better on the second try, it's highly likely that the problem is piston ring/bore related rather than valve seepage.