Rebuilding Oil Pump [WAS: Swapping 345 oil pan]

[jlandry@domain.elided (John A. Landry)]

When he stopped taking his medication, strange voices in "Eppinger.Michael"
<Eppinger.Michael@domain.elided>'s head said:

>From what I understand, the scout II oil pumps are not available new or
>rebuilt, but you can get a rebuild kit for them  (Mollins?  ~$30).

I ordered an oil pump rebuild kit from Northern Auto Parts Warehouse
(www.naparts.com) for just $31.00.  It was manufactured by Federal-Mogul.
I'm 99% sure the same kit is used to rebuild all oil pumps used on IH V8
gasoline engines.  The only difference being which gasket you choose from
the kit during reassembly (tossing the others out).  The kit includes new
pumps gears with pump shaft, o-rings, gaskets, pressure relief spring, and
a few other sundry parts.

The rebuild is really simple and the IH shop manual covers the procedures
and specs in detail.  I just did a Scout II pump and found everything
within tolerance except the play between the side of the new pump gears and
the pump body.  To check this you hold the pump gear away from the pump
wall and check clearance with a feeler gauge.  There's nothing that can be
done to correct this except to replace the pump body.  Wear in the pump
shaft hole is what causes the excess play.  However, with everything else
being well within spec, I don't think the excess play is significant.  John
Stricker has mentioned that worn out rocker to rocker arm and engine
bearing clearances are a much bigger factor in determining how much oil
pressure you're going to have.  I agree... the oil pumps get blamed way too
often as the cause for low pressure.

As has been pointed out by many good mechanics here on the Digest over the
years, one variable that can and must be controlled is the pump gear end
play.  Upon reassembly, the end play is adjusted as needed by adding or
subtracting mylar gaskets from the cover plate.  In the kit, they give you
two .003" thick mylar gaskets to take care of this.  I wound up using 1
gasket and have the tolerance on the tight side but within spec.

The most difficult part of the rebuild job is taping out the old pump shaft
from the collar staked on the shaft.  I simply let the shaft slide down so
the collar was up against the pump body and taped in out with a large
punch.  The new collar must be carefully located on the new shaft and
stacked in place using a suitable punch or blunt chisel.  Easier done than
described.

Not including a soak overnight in carb dip to clean the pump components,
the whole job takes less than an hour if you go through all the trouble to
check all the dimensions and pump gear backlash (like I did).  If you're
installing the rebuild kit, there's probably not much point in checking the
gear backlash, etc., unless you want peace of mind or the pump is *really*
worn out and sloppy.  The backlash tolerance is huge and mine came out on
the tight side.  Wasn't even worth the bother to set up the dial indicator
really.

>Pretty
>easy job to rebuild, I think John L posted to the digest, the rebuild
>technique. It was really good, and I wish I kept a copy of it.

I don't think this was me as I just did my first one last weekend.  Was it
Owen Minor???  In any case, the IH shop manual has a very good step by step
procedure.

Have fun,

John L.
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