[SEL] OT - expansion of metals in oil pumps

jbcast at charter.net jbcast at charter.net
Mon Mar 28 19:30:42 PST 2005



> 
> 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.
> 
Most pumps are designed with extra capacity, oil is flowing through the bypass above idle. The earlier Buick carbureted 3.8L had an undersize oil pump. An aftermarket kit had longer gears and a spacer plate to increase volume.
J.B. Castagnos




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