36 Pontiac Oil Pump rebuild

[Randiego]

Hey all,

I am in the process of a ground up restoration on my 36 Business Coupe.  I am in process with finishing another car before I can get to the Pontiac in earnest.  However, knowing how costs escalate with time, I am doing the drive train and the rest of the car can wait till I can get to it.  I have my engine at the machine shop.  It has been fun finding some items, i.e. over sized  crank and rod bearings.  Pistons were not a problem.  Egge in LA made me new ones.  But finding over sized bearings before we machined the crank (20 over on the mains and 10 under on the rod journals) was a big hunt, but we got them and so on to the next item.          The oil pump.

 

No new oil pumps for 36 are available from the sources that we contacted.  Maybe there are some parts houses or individuals who may have one, but for the month that I looked, I was not successful in my hunt.  Every body has the "rebuild kit" but for my year, but it  is wrong and I will tell  you why.  In the kit, you get two new gears, the shaft and three gaskets.  First of all, the shaft is too short and there is no key way machined in it for the wood ruff key.  And there is no hole drilled into the shaft to accept the pin for the drive gear.  Have you ever tried to drill hardened steel?  Not for the meek. SO after spending $70+ on the rebuild kit, I was not about to go down to the machinist and have a new shaft made, drilled and a key way cut.  That would have cost more than a new pump (if you could find one).  So improvisation was in order.  

 

 For those of us who do not work for a rebuild or restoration shop, and we like to get our hands dirty, this is a pretty  straight forward job (if your oil pump is not too far gone).   I have attached pictures to show the steps that I took to get my oil pump back to "like new" stats. The pictures are large files and I am limited to how many I can attach so there will be several postings showing the progress of the rebuild.

 

This first picture shows the components (with out the oil pump body)  laid out.  Two pump gears, drive shaft with the drive gear on one end and the gear cover plate.  Notice the cover plate is nice and shiny.  When I first took the pump apart, there were groves approximately 10 to 12 thousandths deep.  Not too bad but definitely needing servicing.  How I serviced the cover plate was to take 250 carborundum (or oxide or you choice of good abrasive paper), and lay it on a flat surface.  My work bench has an area that has a steel surface just for this purpose.  I laid the paper flat on the bench and took the cover plate and proceeded to "lap" the plate in circular motion constantly checking to see the progress.  When it was totally smooth and the telltale grooves disappeared, I was done with that step.  Be sure to wash the cover and clean it of any and all grit.  Grit will make short order of an newly rebuilt engine let alone the pump. 

 

The second picture shows the pump body with the wear groves in one of the recesses.  This side of the pump houses the drive shaft with the keyed gear on the pump end.  Notice the second stub in the pump.  This shaft sticks up, not allowing me to lap the surface of the pump. why that is of note here is that if you are to lap the 1 1/2" recess where the gear sits at the bottom, you have to lap the surface to ensure that there is no clearance or you will not have good oil pressure as oil will escape at the end of the gear.   I am sure that if you wanted to get it completely smooth, you can take a torch, heat the body and extract the pin.  Then you can use a 1 1/2" washer with applicable sand paper and shaft attached to "spin" the washer to remove the grooves.  In my case, the wear was minute on the inside of the pump and since I have the cover plate smooth, the loss of pressure will be negligible.   

 

The third picture shows the shaft in the housing with the key way visible.  This is the tricky part.  When you do the re assembly, you have to be sure to have the key way in the gear and the key way in the shaft (with the wood ruff key in place) perfectly aligned.  I did not heat the gear but used copious amounts of assembly lube when I was pressing the gear back on the shaft, going slowly and checking the alignment.  I was fortunate that it was perfectly aligned and the gear pressed on without a hitch.

 

The fourth picture shows the wood ruff key in place. 

 

The fifth picture shows me pressing the gear onto the shaft in my hydraulic press.  When the gear becomes flush with the shaft, you need a drift to continue the pressing.  In my case (next picture), my trusty 1/2" drive Craftsman socket came to the rescue.  It did not take a lot of pressure and no harm was done to the socket.  If you have a piece of suitable pipe in the right dimensions, you can use that.  (My socket is squared and true, hence me using the socket).  Be sure to oil the shaft to enhance the press.

 

This is all that the forum has digital size for so I will sign off for now.  I will continue in the next post.

 

Randy 

 

 

 

 

 

[Randiego]

I am trying to upload more pictures and complete the story however, the Forum does not allow more than 19.53 megabytes per entry.  How do I get more pics attached to this to complete the rebuild procedure?