Re: [Amc-list] The '65 American 330 cranks - now to figure why it won't start

[Tom Jennings <tomj@xxxxxxx>]

On Thu, 21 Feb 2008, jerijan baldwin wrote:

I think your advice is excellent.

> While your plugs are out...DO A COMPRESSION TEST.  Extremely important.

Yeah, good advice. I think you're dead on, but here's a few
other thoughts that apply ONLY! to an old (umm, antique, we're
talking about reviving antique motors ...!) motor.

I wouldn't freak out at initial cylinder variations of even 20%
or maybe more on a just-un-frozen motor. Yeah, it is bad, but
then, so's letting a motor get stuck in the first place! (Not
to blame the person reviving it -- the harm as done innocently
in the far past.) Any life you get out of an abandoned,
once-stuck motor is a FREEBIE and a BLESSING (and not to be
fully trusted :-).


> Why?  A sleeping engine may choose not to make compression adequate to start
> the car.  (the rings seize onto the pistons allowing for blow by.  The
> valves fail to close completely.  Rings may be broken (from the 'freeup'
> process).  So do the compression test.  It'll save lots of troubles later
> on.

Amen. If you get 130, 120, 110, 100, 55, 120  -- oopsie, gots us
a problem! No sense bothering with new plugs on this motor! But
if there's enough compression to run (that 55 was a 100
instead...) rings could un-stick and all come up OK -- or
break! -- in that first hour of operation.

Also, as motors get old, compression variation increases. The
motor I built in 1989, nearly 200K on the rebuild, is now 110
- 130, well out of spec (was near 150) (from memory, too lazy
to get my notebook), but simply wear over 20 years, I measured
compression every 2 - 3 years. It's coming out for re-ring etc
next month.

But to find a "mystery" motor like that, getting it running is
still worthwhile, since you get SOME life out of it and get
to eval the rest of the car and driveline. But it will need
yanking soon enough!!

> including one detonated piston (a hole on the edge) and all four with broken
> rings FLOPPING about in a widened ring grove.  Unsalvageable Engine without

Yeah, holes do tend to lower compression...!

> (One bright side: sometimes 'tired' engines will continue to awaken slowly.
> My '67 did just that.  30,171 miles and a constant skip (probably a valve).
> Inside of a few hundred miles all compression is fine now (thank you God))

That's what happened on this American's 195.6OHV. OK I had to do
a valve job, but it runs like a watch. (A watch that drips oil.)

That reminds me, I should do another compression check this
month and compare against the last one!

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