Cylinder leak down test

[daren007]

What should I use for my base psi and what should I expect for differential on a "A" and "B" engine. I expect the "A" and "B" to be the same.


Thanks.

[MikeK]

That depends on your tester. If it has a true calibrated 0.040" orifice the mfg. instructions likely call for anything in the 50-100psi range. The % difference (not the mathematical subtraction difference) between supply and measured pressure is your result. 5% excellent, 10% OK, 20% tired/ needs service.

[BRENT in 10-uh-C]

Mike pretty much has it covered. The biggest issue we have at the higher pressure is to keep the engine from rotating.


One other thing to realize is your readings is more about comparison at a later date than between each cylinder -or between an A or B engine. We use the tester to listen/look for leaks on an A engine. On modern race engines, we use them for comparison between races. Checking between every couple races allows us to see if a problem is developing such as a scored cylinder wall, head gasket, or leaking valve. In that scenario, comparing data between races sets a baseline to compare to when things do start to deteriorate.

[Jim Brierley]

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Leak-down testing is very importent on race engines. I think not so much on a low compression engine like the A. A compression test usually will tell you all you need to know, quicker and easier than a leak-down.