[Healeys] Compression test

Richard Ewald richard.ewald at gmail.com
Thu Dec 13 10:55:00 MST 2007

I have always considered a compression test to be crude at best at
pinpointing problems.  The readings given tend to make me also look at
piston to wall clearance on the motor.  Off the top of my head, I don't
recall ever seeing readings where cold compression was higher than warm
No knowing the compression ratio of the engine it is hard to say just how
low these readings are from expected.
My gut feeling is that there is a piston to wall clearance problem or some
seriously worn cylinder bores.  If I were my engine I would tear it down and
measure the bores both length wise and crosswise at the top and bottom to
check for ovality and taper.  I suspect that you will find they are oval.  I
know MGB engines wear that way, I suspect that an A engine would also.

On 12/13/07, Warthodson at aol.com <Warthodson at aol.com> wrote:
> I would think that the increase due to oil would point to rings rather
> than
> valves. A leak down test should help pinpoint the cause of low
> compression. If
> it is an intake valve you will hear a faint hissing sound when you listen
> into
> a carburetor. If it is an exhaust valve you will hear it in the exhaust
> pipe.
> Gary Hodson
> In a message dated 12/12/2007 2:26:48 PM Central Standard Time,
> Awgertoo at aol.com writes:
> It seems that cylinder #3 is low by about 10-15% across the  board.   But
> does the fact that the oil squirt raised all readings up  proportionally
> point
> toward a bad exhaust valve?  Would a leakdown test be  any more
> significant?
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