Oil Pump Specs

I took that oil pump for my 8N apart this afternoon.
Gears look good, cover has rub marks from the gears but no deep gouges.

Shop manual lists all the specs for the bushings and shafts but
doesn't list a spec for longitudinal play in the driving shaft once
assembled. Nothing about gear to cover clearance either.
Is there such a spec?

There is an old timer down the road
from me. Has his own tractor and
hay implement shop now. He used to
work at the Ford tractor dealer when
I was a kid. So this fellas has some
vintage on him. I was picking his
brain about this oil pump deal a few
years ago. He told me .001 to.002.
.003 max. He said use plasti-gauge
just like a rod or main bearing. So,
I figure he knows what he is talking
about. This clearance will only
affect wetter it self primes or not.
Nothing to do with pressure. But I
am sure you knew that.

I was speaking about gear to cover clearance.

Yep use plastigage and may leave the gasket out. Mine still running with good oil pressure from 1965.

Cowdog/Roger, thank you both.
I'd take it back apart and plastigauge it, but then I'd have
to clean off all that RTV I used to seal it... JUST KIDDING!!
I have .005 longitudinal play with the gasket installed.
Easy enough to pull the cover and gasket back off and check.
Sounds like it's pretty darn close though. Good to know.

(quoted from post at 21:07:33 10/15/17) Cowdog/Roger, thank you both.
I'd take it back apart and plastigauge it, but then I'd have
to clean off all that RTV I used to seal it... JUST KIDDING!!
I have .005 longitudinal play with the gasket installed.
Easy enough to pull the cover and gasket back off and check.
Sounds like it's pretty darn close though. Good to know.

Click to expand...

When I install the new drive gear I press it on such that there is no measurable end play and the gear spins with no signs of drag. End clearance of .001/.003 between gear and cover would be ideal. In my experience good gears are dead flush with the surface of a good housing and the gasket is what produces the clearance. In a gear pump end clearance is a a primary source of "slip" and if excessive will most definitely affect pressure and volume. Ideal tip clearance is about the same.

Per the industrial engine shop manual running clearance on the shaft should be .001/.0015. New shafts consistently measure .0005/.001 under the 9/16 nominal size and I use a standard (.000/.0005 over) reamer. That usually comes out pretty tight.

TOH

(quoted from post at 21:37:08 10/15/17)

(quoted from post at 21:07:33 10/15/17) Cowdog/Roger, thank you both.
I'd take it back apart and plastigauge it, but then I'd have
to clean off all that RTV I used to seal it... JUST KIDDING!!
I have .005 longitudinal play with the gasket installed.
Easy enough to pull the cover and gasket back off and check.
Sounds like it's pretty darn close though. Good to know.

Click to expand...

When I install the new drive gear I press it on such that there is no measurable end play and the gear spins with no signs of drag. End clearance of .001/.003 between gear and cover would be ideal. In my experience good gears are dead flush with the surface of a good housing and the gasket is what produces the clearance. In a gear pump end clearance is a a primary source of "slip" and if excessive will most definitely affect pressure and volume. Ideal tip clearance is about the same.

Per the industrial engine shop manual running clearance on the shaft should be .001/.0015. New shafts consistently measure .0005/.001 under the 9/16 nominal size and I use a standard (.000/.0005 over) reamer. That usually comes out pretty tight.

TOH

Click to expand...

Thanks TOH. Another thought came to me. How much longitudinal movement should there be without the cover on, drive gears both in place?

(quoted from post at 21:51:39 10/15/17)

(quoted from post at 21:37:08 10/15/17)

(quoted from post at 21:07:33 10/15/17) Cowdog/Roger, thank you both.
I'd take it back apart and plastigauge it, but then I'd have
to clean off all that RTV I used to seal it... JUST KIDDING!!
I have .005 longitudinal play with the gasket installed.
Easy enough to pull the cover and gasket back off and check.
Sounds like it's pretty darn close though. Good to know.

Click to expand...

When I install the new drive gear I press it on such that there is no measurable end play and the gear spins with no signs of drag. End clearance of .001/.003 between gear and cover would be ideal. In my experience good gears are dead flush with the surface of a good housing and the gasket is what produces the clearance. In a gear pump end clearance is a a primary source of "slip" and if excessive will most definitely affect pressure and volume. Ideal tip clearance is about the same.

Per the industrial engine shop manual running clearance on the shaft should be .001/.0015. New shafts consistently measure .0005/.001 under the 9/16 nominal size and I use a standard (.000/.0005 over) reamer. That usually comes out pretty tight.

TOH

Click to expand...

Thanks TOH. Another thought came to me. How much longitudinal movement should there be without the cover on, drive gears both in place?

Click to expand...

I interpret "longitudinal" to mean end play and I assemble them by pressing the gear on enough there is no end play. If you mean backlash the call out on the factory prints was .003/.006. I assume that specification was meant to be clearance normal to the tooth as measured with a feeler gauge.

TOH

(quoted from post at 23:05:41 10/15/17)

(quoted from post at 21:51:39 10/15/17)

(quoted from post at 21:37:08 10/15/17)

(quoted from post at 21:07:33 10/15/17) Cowdog/Roger, thank you both.
I'd take it back apart and plastigauge it, but then I'd have
to clean off all that RTV I used to seal it... JUST KIDDING!!
I have .005 longitudinal play with the gasket installed.
Easy enough to pull the cover and gasket back off and check.
Sounds like it's pretty darn close though. Good to know.

Click to expand...

When I install the new drive gear I press it on such that there is no measurable end play and the gear spins with no signs of drag. End clearance of .001/.003 between gear and cover would be ideal. In my experience good gears are dead flush with the surface of a good housing and the gasket is what produces the clearance. In a gear pump end clearance is a a primary source of "slip" and if excessive will most definitely affect pressure and volume. Ideal tip clearance is about the same.

Per the industrial engine shop manual running clearance on the shaft should be .001/.0015. New shafts consistently measure .0005/.001 under the 9/16 nominal size and I use a standard (.000/.0005 over) reamer. That usually comes out pretty tight.

TOH

Click to expand...

Thanks TOH. Another thought came to me. How much longitudinal movement should there be without the cover on, drive gears both in place?

Click to expand...

I interpret "longitudinal" to mean end play and I assemble them by pressing the gear on enough there is no end play. If you mean backlash the call out on the factory prints was .003/.006. I assume that specification was meant to be clearance normal to the tooth as measured with a feeler gauge.

TOH

Click to expand...

Longitudinal meaning in the direction of the length of the shaft.
I have the internal pump drive gear installed and the external
drive gear installed on the opposite end of the same shaft.
I'm wondering how much the shaft should move in and out lengthwise.
No tooth mesh or backlash involved in this measurement as it
is more end play as you termed it. Not rotational at all.
Same measurement I was making with the cover installed as well.
The reason for concern were the rub marks on the cover.
Seems like there should have been a small clearance there.
As others have said, .001 to .003. Not rubbing. No?

(quoted from post at 23:22:23 10/15/17)

(quoted from post at 23:05:41 10/15/17)

(quoted from post at 21:51:39 10/15/17)

(quoted from post at 21:37:08 10/15/17)

(quoted from post at 21:07:33 10/15/17) Cowdog/Roger, thank you both.
I'd take it back apart and plastigauge it, but then I'd have
to clean off all that RTV I used to seal it... JUST KIDDING!!
I have .005 longitudinal play with the gasket installed.
Easy enough to pull the cover and gasket back off and check.
Sounds like it's pretty darn close though. Good to know.

Click to expand...

When I install the new drive gear I press it on such that there is no measurable end play and the gear spins with no signs of drag. End clearance of .001/.003 between gear and cover would be ideal. In my experience good gears are dead flush with the surface of a good housing and the gasket is what produces the clearance. In a gear pump end clearance is a a primary source of "slip" and if excessive will most definitely affect pressure and volume. Ideal tip clearance is about the same.

Per the industrial engine shop manual running clearance on the shaft should be .001/.0015. New shafts consistently measure .0005/.001 under the 9/16 nominal size and I use a standard (.000/.0005 over) reamer. That usually comes out pretty tight.

TOH

Click to expand...

Thanks TOH. Another thought came to me. How much longitudinal movement should there be without the cover on, drive gears both in place?

Click to expand...

I interpret "longitudinal" to mean end play and I assemble them by pressing the gear on enough there is no end play. If you mean backlash the call out on the factory prints was .003/.006. I assume that specification was meant to be clearance normal to the tooth as measured with a feeler gauge.

TOH

Click to expand...

Longitudinal meaning in the direction of the length of the shaft.
I have the internal pump drive gear installed and the external
drive gear installed on the opposite end of the same shaft.
I'm wondering how much the shaft should move in and out lengthwise.
No tooth mesh or backlash involved in this measurement as it
is more end play as you termed it. Not rotational at all.
Same measurement I was making with the cover installed as well.
The reason for concern were the rub marks on the cover.
Seems like there should have been a small clearance there.
As others have said, .001 to .003. Not rubbing. No?

Click to expand...

Remove any scoring on the cover by lapping or grinding on a flat surface. That mainly comes from a worn shaft bushing that allows the drive gear to wobble and the edges of the teeth dig into the cover.

The movement you are describing is shaft end play and I take all of that out. I put it in a press with big gear on the bottom and press the smaller gear on testing end play/rotational freedom by moving the body on the shaft as I pump the press. You can get it dead on the numbers that way - virtually no end play and the shaft still rotates freely. If you overshoot slightly and get it too tight just use a punch to tap the shaft back out an RCH. That is machinist jargon for a very small amount ;-) If the gear rubs on the sidewall after it is press on you botched the bushing - try again with a new bushing.

After you have that part right drop the driven gear in and check for binding between the pump gears. If there is interference you didn't get the bushing reamed concentric to the bore in the body and the center distance between the gears is off. Try again with a new bushing.

Measure end clearance with a feeler gauge and machinist straight edge laid across the face of the housing. Add the thickness of the gasket to get nominal oil clearance. The smaller the clearance the better but that depends largely on gear and housing dimensions/wear.

TOH