1) Aircraft engine leakdown tests are typically done with 80psi. Look
in the engine logbook for private plane and you'll see that
compression/leakdown readings are expressed as a fraction of 80. Maybe
an engine you intend to operate in denser air should be leakdown tested
at a higher pressure, but I'm only guessing when I say that.
2) Good question. I suppose as long as you know all the valves are
completely closed, you're just varying where the rings are in the
(possibly tapered) cylinder. Maybe halfway up the compression stroke,
assuming the cams aren't too agressive?
3) Like compression readings, having all the cylinders read close to
each other is sometimes considered more important than an absolute
number. If I had to choose between an engine with 70, 79, 79, 79 for
the 4 readings versus 76 for all four, I'd pick the second one.
keithka@microsoft.com
seeking bargain vintage project (pref. open wheel) or Crossle CF
>----------
>From: ps4330@okc01.rb.jccbi.gov[SMTP:ps4330@okc01.rb.jccbi.gov]
>Sent: Wednesday, January 08, 1997 1:33 PM
>To: shop-talk@autox.team.net
>Subject: Leak-down test
>
>Questions about doing a leak-down test:
>
>1. How much pressure should I use?
>
>2. What position should the piston be in (tdc on the firing stroke )?
>
>3. What constitutes a "good" reading? How do I interpret the results?
>
>thanks,
>
>Peter Schauss
>ps4330@okc01.rb.jccbi.gov
>schauss@worldnet.att.net
>1963 Austin-Healey 3000 Mk II
>1980 MGB
>
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