Re: [Amc-list] Fwd: Davis Martin's Oil Pump Kit (was: 401 Oil Mods from 03-15-2008)

[Tom Jennings <tomj@xxxxxxx>]

On Fri, 2 May 2008, Greg Taylor wrote:

Thanks Greg!

This is the important part:


> Davis Martin <martin-davis@xxxxxxxxxxxxx> wrote:

> OK, on to poor oil pressure.
> The problem with the stock setup is there is a Powdered Iron
> gear living in an aluminum housing. The 2 have very different
> expansion coefficient's. So when you set your nice tight pump
> clearances on the bench they do not hold up. When the engine
> heats to operating temp, the gear does not expand as much as the
> housing, and you have a looser pump then optimum. This is why
> most see warm engine pressures in 18 PSI or lower.

> The fix.

> Bill figured this out 20 years ago when we were loosing
> bearings. He found an alloy with the same expansion coefficient
> as the timing cover. We have gears made from this alloy which is
> harder on the RC scale then the factory gears. Once we swapped
> to this set up our amc oil problems were no longer.

Very clever!

So warm-engine-oil-pressure-drop is not dominated by the oil
thinning as it gets warm? I always assumed it was that! I don't
own an AMC V8, and all my sixes have cast iron pumps --but no oil
pressure guages. I assume there's some temp-related-oil-thinning
pressure drop?

It does seem to be the weak part of the AMC 8, that aluminum
timing cover.

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