Reply to "Those damn little Elves switched my Windsor out for a Cleveland!"

Hi Steve,

Run a compression test first, all plugs removed, carb set wide open, cranking with the starter. Look for uniformity among the readings, if they all check within 10% go on to the leak down test.

Assuming the leakdown tester is set correctly & in good working order, assuming each cylinder tested is set at TDC on the compression stroke, an average number is 5%, 2% is excellent, anything worse than 10% is taken as a sign of trouble. However, uniformity plays a factor here as well.

If all test good at TDC, test each cylinder at a few settings past TDC by rotating the crank a bit, a cylinder may have a problem in a cylinder wall somewhere in the middle of the stroke.

To detect small leaks it is sometimes necessary to reduce the pressure setting of the tester, less pressure flows less air through the tester's orifice, and leaks will create a greater pressure drop, makng the tester more sensitive to small leaks.

The compression & leak down tests together tell the whole story.

Did your dyno guys have an O2 sensor in the tailpipe, checking for a lean carb mixture?

George