1950 8N - Oil Pump Replacement/Rebuild

[jsoluna]

Hey everyone,

I've got my hand on an 8n for the first time. Tore into it last week to find out what damage had occured when previous owner put the governor bolt in the wrong hole.

In addition to the cam and crank gears being trashed, I also noticed a lot of play in the pump shaft. When I took it to my bench and inspected, I found wear behind both gears as expected. Has anyone here put a rebuild kit in one of these severely worn pumps? According to the owner, it has 30psi of oil pressure pretty constantly before he killed it. I have read a lot on the proper procedures, and so I understand that the right thing to do is replace the housing and have it lined bored.

I'm trying to get it running before the end of summer and if I pull the engine it won't be until next year I'm sure. I know TOH had one of these worn pumps and was going to test it to see what the wear limit would be for the housings. This one looks to be just as bad as the one he was looking at.

 

[jsoluna]

 

[TheOldHokie]

(quoted from post at 06:05:20 07/29/19) Hey everyone,

I've got my hand on an 8n for the first time. Tore into it last week to find out what damage had occured when previous owner put the governor bolt in the wrong hole.

In addition to the cam and crank gears being trashed, I also noticed a lot of play in the pump shaft. When I took it to my bench and inspected, I found wear behind both gears as expected. Has anyone here put a rebuild kit in one of these severely worn pumps? According to the owner, it has 30psi of oil pressure pretty constantly before he killed it. I have read a lot on the proper procedures, and so I understand that the right thing to do is replace the housing and have it lined bored.

I'm trying to get it running before the end of summer and if I pull the engine it won't be until next year I'm sure. I know TOH had one of these worn pumps and was going to test it to see what the wear limit would be for the housings. This one looks to be just as bad as the one he was looking at.

I have looked at a lot of these and some really bad ones work just fine and some nice looking ones don't work worth a pi$$. The only reliable test is in a running engine which of course adds all sorts of other variables into the mix.

Given your situation I'd put a new bushing and gears in it and run it to see how it does. If you have done your research you know how that needs to be done. You can always do the housing replacement and line hone when/if you get around to a full overhaul. Just make sure the new gears are the proper width - "9/16" gears should measure .561/.562 and "3/4" should measure .724/.725. That is not a typo - the wider gears are actually quite a bit narrower than nominal. There are a lot of bogus rebuild kits with undersize gears on the market and price is a good but not perfect indicator of which ones are OK and which ones are not :evil:

TOH

 

[jsoluna]

Thanks for the reply! I had mic'd mine and they measured .7245 and .7240 so they are probably original along with the bushing. I did see where the 3/4 nominal gears are being made in the .7110 size and that's just nuts man.

You still offer to do the rebuilds?

 

[TheOldHokie]

(quoted from post at 11:39:56 07/29/19)
Thanks for the reply! I had mic'd mine and they measured .7245 and .7240 so they are probably original along with the bushing. I did see where the 3/4 nominal gears are being made in the .7110 size and that's just nuts man.

You still offer to do the rebuilds?

I still do the rebuilds. It costs $25 plus parts.

TOH

 

[jsoluna]

Awesome. May send mine out to you to make sure the bushing is reamed true to the housing and give it the best chance for the future. Looks like I'm not able to PM you, so if you would message me your details I'd appreciate it.

Look at the gear mesh. You can see just how much of the drive gear tooth pitch is gone. Main bearing still looked pretty good though. May be a blessing in disguise that this engine was taken out of service. I do plan on replacing the pickup tube and pump end cover assembly, by the way.

 

[jsoluna]

Further teardown:

 

[TheOldHokie]

(quoted from post at 19:19:16 07/29/19)
Awesome. May send mine out to you to make sure the bushing is reamed true to the housing and give it the best chance for the future. Looks like I'm not able to PM you, so if you would message me your details I'd appreciate it.


Look at the gear mesh. You can see just how much of the drive gear tooth pitch is gone. Main bearing still looked pretty good though. May be a blessing in disguise that this engine was taken out of service. I do plan on replacing the pickup tube and pump end cover assembly, by the way.

The forum's PM feature has been disabled for years now. My email is [email protected]

TOH