MC with really low compression

ed armstrong
Mon, 7 May 2001 14:04:08 -0700 (PDT)


I thought handcranking the pistons might be the "X"
factor in this test. Obviously I can't match the speed
or intensity of the starter.

Is there another vote out there that handcranking is a
no-no for compression tests?? That would make me feel
a whole lot better about this engine.

- ed

--- Bernard Littau <>
> > Out of curiosity, I ran a compression test on all
> > cylinders and the results blew my mind! The best I
> > could get out of one cylinder was 40 psi and the
> > others were around 30 or so. I was expecting
> readings
> > in the low-mid 100s with an engine with 144K miles
> on
> > it. I was just handcranking the pistons but I did
> many
> > times over. I was planning to do the head with new
> > valves and guides anyway, but this soundz more
> serious
> > now. I'll now more next weekend when I pull the
> head.
> Hi Ed,
> Hand crank numbers are not comparable.  The
> compression test must be run
> with a strong battery, all plugs out, and with the
> throttle body wide open.
> I think Bentley wants five or ten compression
> strokes per cylinder, too.
> The speed of the cranking has much to do with the
> compression numbers -- the
> faster you crank, the less apparent leakage.
> Best,
> Bernard Littau
> Woodinville, WA
> '88 5ktq

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