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Author Topic: FJ grey motor oil pump gears  (Read 406 times)
johnrap
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« on: July 24, 2021, 03:54:26 PM »
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Hi
Can anyone assist with a good set of oil pump gears for grey motor in a FJ.
I have a gear set from a grey motor L block but the shaft diameter seems to be
Bigger.

Any help appreciated

Thanks
John
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ardiesse
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« Reply #1 on: July 24, 2021, 05:20:57 PM »
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John,

That's strange.  All grey motor oil pump gears are the same (except . . . some were helical gears, and some were spur gears).

It is possible that this oil pump has had a red motor gearset fitted.  Red motor gears (spur, not helical) have a smaller shaft diameter.  Are the ones in the oil pump spur gears?

If you have a vernier caliper, post some measurements, and I'll try to make sense of them.

Rob
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johnrap
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« Reply #2 on: July 25, 2021, 12:59:20 PM »
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Hi Rob
The measurement of the oil pump shaft that I removed from the failed FJ engine measures 14.15.

The spare oil pump shaft I have measures 14.20
Sitting them side by side they look identical.

The main pump body of the pump removed from the damaged FJ engine has a part number 7409385

I do have another pump body it has a different part number 7400883. My spare oil pump shaft doesn’t fit this body or the damaged FJ  engine pump body.

I did notice that the pump out of the damaged engine when you look down from the top
Where the two pump gears sit at the bottom, the one out of the FJ damaged engine is
pretty flat with the casting where the two gears sit.

The spare pump body 7400883 I have that area is is raised.

Measuring from top of pump to bottom of where the gears sit
The damaged FJ engine pump part number 7409385 measures 25.51
The spare body part number 7400883 measures 25.17

This engine had a previous failure the tongue from the dizzy that drives the oil pump sheared off.
Also when I stripped the oil pump from the damaged FJ engine their was no gasket between the two half’s of the pump
as per the FJ manual.

Looking in the FJ manual the pump out of the damaged FJ  engine I am working on is as per the manual it has the same
Pressure relief valve set up as per the illustrations in the manual.

Appreciate  you help Rob.

Regards John

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ardiesse
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« Reply #3 on: July 25, 2021, 02:12:35 PM »
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John,

All grey motor oil pumps interchange as complete assemblies, but you can come unstuck playing mix'n'match.  My 1957 master parts catalog says that the oil pump was revised during the FJ, at engine number 197343.  The parts catalog doesn't list part numbers for the oil pump housing, only the complete pump.  But - the 740883 housing is definitely FX-early FJ, and will have the squarer-looking pickup and screen.  The 7409385 housing is the later version, and takes the hamburger-bun-shaped pickup screen.  The oil pump illustrated in the FJ shop manual is the early pump.

The earlier style pump takes the gasket between the body and cover, the later style pump doesn't appear to.  The gasket's optional, really.  Whether you use one depends on the difference in height of the gearset and the depth of the oil pump body.  If the gears turn freely without the gasket fitted, then you don't need the gasket.  I would not be surprised if the failed pump has worn the body where the gears run, explaining the extra 0.3 mm depth.

Drive gear shafts: Fifty microns (14.20 - 14.15) is about 0.002", which is almost within production tolerances plus a little bit of wear.  I wonder whether your spare oil pump drive gear has an oversize shaft - you'd need to get the pump body reamed out to suit, if you were going to use it.

What to do: use the pump that's in the best condition, as long as it's complete with pickup screen and pressure relief valve.  You'd also be surprised how much wear you can tolerate in the gears before it affects the oil pressure.

Rob
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« Reply #4 on: July 26, 2021, 03:06:56 PM »
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Hi Rob
Thanks for your reply’s  on this subject.

Regards
John
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ardiesse
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« Reply #5 on: July 30, 2021, 08:44:44 PM »
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John,

I've discovered some more information about oil pumps.  Go to -

https://hrc.org.au/holden/accelerator.html and open the August 1960 issue.  The oil pump was revised again during the FB.

Rob
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