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

[Wrambler242@xxxxxxxxxxx]

I watched mine last time I ran it and the pressure varied very little from cold too hot.
[read that way too much]....
I dearly hope I can squeeze enough feeling good time and spare time together and get the rear cover sealed up to I can at least get it out and run it to lubricate everything good!

--
Mark Price
Morgantown, WV
1969 AMC Rambler, 4.0L, EFI, T-5
2004 Grand Cherokee Laredo, 4.7L, Quadratrc II
" Chronic Pain Hurts"

 -------------- Original message ----------------------
From: 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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