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Re: Leak-down test

Subject: Re: Leak-down test
Date: Thu, 9 Jan 1997 10:45:50 -0500 (EST) (Peter Schauss) wrote:

>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?


>Peter Schauss

A store-bought leakdown tester one of my bosses at work has has the calibrate
line at 35PSI (It's not labeled, I measured it).
around probably 35-30 PSI was good, 15 or 20-30psi was acceptable, and <
15psi was bad.  One problem with this one is it had an orifice that was
probably calibrated for a certain size cylinder, and larger or smaller ones
whould read worse or better, respectively, than they actually were. (Note
this applies to wear, not stuck open valves or broken rings/gouged cyl walls)

I would recommend getting a baseline of what a good cylinder is (one that was
rebuilt, and then properly broken in), or else use the 20% of reading
difference that someone else mentioned.

Should have the piston @ TDC with both valves closed-make sure it's right on
TDC, or is may spin the engine over a partial revolution.

PS: The orifice in the leakdown tester I saw was in brass around .050 thick,
and around a .015" hole.

Scott M Ryan

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