[SEL] OT - expansion of metals in oil pumps

[Listerdiesel]

On Mon, 28 Mar 2005 18:46:44 -0600, Bill Dickerson
<bill at antique-engines.com> wrote:
> 
> For the engineers - rob, etc.
> 
> Engine oil pump - automotive gear type. Gears are steel (or some sort of
> steel product) housing is aluminum - timing chain cover with pump body in
> the timing cover.
> The gear to housing end clearance is supposed to be VERY close to get the
> pump to put out good pressure.
> A lot of folks say this is a weak design - that the aluminum will expand
> more and open clearances between the gears and the housing.
> They claim the fix is to use aluminum gears in the alum housing so they
> expand at the same rate, meaning a more accurate and tight pump, longer
> life, higher pressure, etc.
> 
> Thoughts?
> 
> Bill

Ali will hold metal parts in the gear teeth surface, causing
accelerated wear, while hardened steel gears won't. It's a wear thing
more than anything else, and as has already been pointed out, you pump
much more oil than you actually need so there is an allowance for wear
and tear.

I'd guess that if you had something very exotic like Titanium which
work hardens then it might be a starter, but I'd stay with steel gears
myself.

Peter
-- 
Peter A Forbes
Email: listerdiesel at gmail.com
Web: www.oldengine.org/members/diesel