leak-down test

kieran12

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anybody know the time to wait in this test -

The information I have regarding leak down for automotive engines indicates the following:

3% to 5% - good racing engine
5% to 7% - good street engine
10% - weak
20% - shot

BUT - how long to wait ?? thanx
 
From racing, nothing to do with aircraft, We check to see how good a job we did building the motor with the leak down and use that as our base line. After each race we do it again and form trends. We run it on the dyno at different leak downs and see how much it matters. In my experiance when it starts changing rapidly it is time to adress the problems. Valves, as they begin to leak, don't cool as well and get worse. Rings, as they began to leak burn the oil coating the top of the cylinder and the condition deterioates rapidly. So in my opinion if you do a leak down every time you change your oil, you will be able to spot a downward trend. In racing we always found it less expensive to rebuild sooner rather than later.

In the higher levels of racing we would ring and valve it every race (300) miles and pull it down to the crank every other race. When running nitro even if nothing went wrong the engine would last about 35 miles wide open. Usualy we didn't make that TBO. Thank you, Vance
 
thanx to all

thanx to all

now i understand -

i just want to check out a soob i have -

i see a few dual gauge type on ebay - thanx again
 
That is good info. I think I will go buy a guage myself.
 
Static VS Dynamic Leak Down

Static VS Dynamic Leak Down

Checking the leak rate of an engine sitting on the work bench is one thing. It is usually the best readings you will get.

From the trenches here, I have had good subs check out on cranking compression, leak down and then when you run them it is a different story.

under load and under stress is the worst readings. (if you could monitor them, dynamic ) The only way you can tell is to have a digital rpm gauge and note readings at certain temp and atmospheric pressures. If you find the engine will not turn up then you REALLY know something is going south, way before you see it on either gauge set.

Jonathan
 
Speaking of pressure.

How do most people vent the crank case and valve covers on carbed EJ-22s?
 
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