Leakdown / compression test

[AFB]

(Disclaimer - forgive my ignorance, motors and anything electrical is like learning Chinese for me)

Hey guys, I have 170K motor that is still running strong but I'd like to think I could dive into rebuilding... or just order a turnkey from Rick I have looked at several informative videos on how to do theses test. My question: Leak down - does it matter which cylinder I test as long as it's at TDC? I've learned that 10% loss of pressure is acceptable... true? (Im cautiously optimistic, I know my motor is tired). Compression what kind of numbers should I be seeing, whats an acceptable percentage difference in cylinders.

Thanks guys, I will likely yank and scrap the motor and just purchase a turn-key, but if nothing else Im going to tear down my existing motor for the experience.

Adam

 

[jrichker]

The recommended procedure is to test each cylinder at TDC. That way you get a true picture of the condition of the engine. Gettiong the piston to exactly TDC is tricky. If you go past TDC, you have to back up at least 90 degrees and go forward to TDC to get the rings seated correctly.

The 10% is a little tight, aircraft piston engines use 64PSI over 80PSI or about 19% as an acceptable leakdown . See the link in my sig to build your own leakdown tester.