I agree with you also Chris, I had an engine with 40% & 25% cylinders, and when we tore it down, they were scored pretty bad. But I am tired of defending leakdown tests over compression test.

Whooo, there is a BIG difference between 28% and 40% leakdown. 28% may be ok, but 40% is BAD. If your worst leak is like the numbers you have, ie 28% worst case, your engine is ok. Unless you are racing for first place wait until your numbers hit something like 35% or more.

By the way the simple compression test of an engine with 28% leakdown and 40% leakdown are likely to be the same. So what does that prove? In fact I just tore down an engine with perfactly good compression numbers that had all broken compression rings! It did, however fail leakdown at something like 40% to 60% numbers. The compression numbers were all 150 plus or minus 5 lbs.

Hmm, 5% leakdown would be ideal. I tend to think anything past 10% is cause for concern. Again, it's only one test - and needs to be considered in conjunction with the others.

Your engine won't self-destruct if the rings are worn - it will just lose a lot of power...

-Wayne

Some of the leakdown testers come with a good, questionable, bad zone printed along with the leakage number. The typical "bad" is 60% or more, good usually extends to 35 or 40%, with the yellow questionable inbetween.

A lot depends on WHY the leakage is high. If, for example, its the valves, and only the valves, with other info to back it up, then a valve job is indicated, and not a complete overhall.

I doubt most cars would show less than 10% leakage. Typical numbers I have seen on BMWs(325, 633, 635, M6(before rebuild), DKW, Porsche(1600,2.2,3.0), VW,MG, Metropolitan, 283, 327, 409, 440, 318, 361, Sunbeam, Kaiser, Jeep, AMC, and several I have completely forgotten about, even a Falcone and DeSoto, when they were running ok ranged between 7% to 30%. There was ALWAYS huge leakdowns, ie 60% or more when there were broken rings. Almost all the ones with broken rings PASSED the compression check test.

Anyway one thing I have noticed is that a good leakdown test can be touchy, ie hard to get good numbers, unless you are very careful to do everything right. I have noticed that a motor with 5% leakdowns can have 15 to30% leakdowns if not up to operating temp, if there is a little carbon build up on the valves, or if the piston isn't in the correct position. Thats my 02 cents worth from some of the cars I have owned.

Chris,

Yes this was %age leakage, and yes 28% is a bit high, but I had a second test done and the figures were lower, as such everything is cool and the gang!

Luke

Luke,

Noticed your in London, where abouts, there seem to be a few of us posting here from the Uk.

Who did those tests by the way.

Saw your purple car pics, very nice.

Cheers,

Michel.

Michel, I've private messaged you.

Luke