Oil pump rebuild

NickZ · Jul 15, 2021

gortnipper said:
Look at swooshdave's video and you can see the pump apart. This is kommando's, but he used an xring.

Does anyone know the specs for the X-ring Kommando used?

gortnipper · Jul 15, 2021

"Does anyone know the specs for the X-ring Kommando used?"

@kommando

kommando · Jul 16, 2021

gortnipper said:
"Does anyone know the specs for the X-ring Kommando used?"

@kommando

The X ring is size 012 in buna shore 70, you need an 1/2" end mill. The X ring is .070" cross section, its compressed by both the shaft and OD of the slot so the extra 0.020" depth of the 0.090" slot takes the side expansion of the X ring.

Example of sizes

Standard Size Charts for Quad-Ring® Seals and X-Ring Seals

www.allorings.com

batrider · Jul 17, 2021

Be careful when lapping. The difference between loose and tight can be just a few swipes on the sandpaper. If you go too far, you're screwed.

kommando · Jul 17, 2021

batrider said:
Be careful when lapping. The difference between loose and tight can be just a few swipes on the sandpaper. If you go too far, you're screwed.

You are not screwed, your next step is to thin the gears, the difficult one is integral to the driven shaft but not insurmountable. Checking often does stop you going too far. I like it a bit tight, I them mount it a lathe and feed it with oil while running it at low revs, this frees the pump off enough.

batrider · Jul 17, 2021

Thin the gears, maybe with a milling machine? Right...
Check often is right, especially when you get close.

kommando · Jul 17, 2021

batrider said:
Thin the gears, maybe with a milling machine? Right...

Emery cloth works but as its harder material it will take longer to remove the same thickness than off the body and end plates, in a fully equipped workshop it would be done on a surface grinder with magnetic table taking tenth's of a thou off each pass. Milling machine tooling would not be up to the task.

chaztuna · Jul 17, 2021

kommando said:
The X ring is size 012 in buna shore 70, you need an 1/2" end mill. The X ring is .070" cross section, its compressed by both the shaft and OD of the slot so the extra 0.020" depth of the 0.090" slot takes the side expansion of the X ring.

snipped

kommando,
If I understand you correctly, you are stating that the 1/2" end mill is used to create a counterbore 0.090" deep. Am I correct?

kommando · Jul 17, 2021

chaztuna said:
If I understand you correctly, you are stating that the 1/2" end mill is used to create a counterbore 0.090" deep. Am I correct?

Yes, same as AMR, I just use the X ring equivalent to the O ring they use.

mdt-son · Jul 18, 2021

Installing an O- or X-ring will give the shafts - especially the driven shaft - less support. The pump is a poor design to start with, and by this mod it gets even poorer. Have you considered that the angular pendulum motion of the driven shaft may increase? It's counteracted by small hydrostatic forces at the feed side, but is this sufficient? How well are the bearing seats of both shafts lubricated? Why are the sealing rings not installed at the scavenge side of the housing instead? I am curious to see a close examination of a pump with the AMR modification and some mileage on it.

-Knut

chaztuna · Jul 18, 2021

mdt-son said:
Installing an O- or X-ring will give the shafts - especially the driven shaft - less support. The pump is a poor design to start with, and by this mod it gets even poorer. Have you considered that the angular pendulum motion of the driven shaft may increase? It's counteracted by small hydrostatic forces at the feed side, but is this sufficient? How well are the bearing seats of both shafts lubricated? Why are the sealing rings not installed at the scavenge side of the housing instead? I am curious to see a close examination of a pump with the AMR modification and some mileage on it.

-Knut

Knut brings up an excellent point. Perhaps part of the issue for those who have wet sumping issues is excessive clearance and/or a rough surface on the bearing surface for the shaft in the oil pump housing. Another possible fix if you have excessive clearance would be to machine the pump body, then fit and ream a bushing to tighten up the shaft to body clearance?

Oil pump rebuild

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