Does anyone have data that shows the difference between leakdown results with the motor cold vs. hot? I've always done it hot but heard some say the difference is negligible.
I tried to do this experiment last night before I pull my old engine using 2 different leakdown tools to also compare the tools but 2 cylinders seem to have nasty valve problems (massive leakdown) so I didn't even want to get the engine hot in order to save whatever good parts are left in this engine.
I figure this info could be useful in testing used engines or different heads while the engine is out of the car. I figure it's not much use on a brand new engine since the rings aren't set yet.
Thanks,
Keith
Leakdown Hot vs. Cold
Started by
Keith Novak
, 01-19-2011 09:02 AM
#1
Posted 01-19-2011 09:02 AM
#2
Posted 01-19-2011 12:48 PM
The reason you want it warmed up is so everything will seat as it would under operating conditions.
#3
Posted 01-19-2011 01:55 PM
The reason you want it warmed up is so everything will seat as it would under operating conditions.
Agreed, that's why I've always done it hot. This came about when I did a leakdown months ago a used engine I bought, and found much better results than the previous owner. I'm not sure whether it's because we used different tools, he did it cold and I did it hot, intake stroke vs. compression stroke, or maybe my leakdown kung-fu is just better than his. I figured I'd test a few possible theories but since then 2 cyliners have gone to hell.
If it's 1% difference cold vs. hot, that would be good enough to say this motor or head sitting in my garage isn't runnoffs strong but still not too shabby. It's a bit better than the test shows since it's cold and that doesn't require installing it and breaking it in first. If it's >10% like the difference between our measurements, it wouldn't be very meaningfull cold at all.
BTW- I think I unintentionally did this as a poll, not a normal thread?
#4
Posted 01-19-2011 03:48 PM
I did a compression test cold before I remembered I had to do it hot and the numbers hot were like 30% better hot.
Frank
TnT Racing
SCCA Ohio Valley Region
#5
Posted 01-19-2011 04:51 PM
That's what I was looking for. Thanks Frank. Sounds like a couple % difference will get lost in the bigger difference between tollerances cold vs. hot.
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