Inliners International Forums General Discussion Engines Oil Pumps

I'm tearing down a 235, block #3837004. Full oil press with alum pistons. The oil pump is held in the block with two pins that have round heads on the outside of the block. On the inside they look like they are threaded??!!>>?? I dont seem to be able to remove the oil pump from the block as it will not budge. I can remove the pick end of the pump, from the gears out but the end from the gears to the block looks to me to be in there for keeps. Any help?

Its kind of a non-serviceable part! The pump body is not removable, but the gears are replaceable. I've heard that back in the day, racers would drill the round head brads out of the pump housings off of a GMC 6 and,reinstall the pump(GMC)onto a 235/261 engine. The pumps were supposed to be higher volume on the GMC's than the Chevy's. Don't know if there is any truth to that or not....If you wanted to go to that extreme to remove it,im sure it could be done!

there is a bolt that holds the pump to the block. it has a nut on it to act as a lock nut or keeper. You have to look for it but you will find it. Loosen the keeper, then the bolt and the pump pulls out the bottom of the block

A close look at Figure 4 in the Chevrolet Shop Manual will reveal the "set screw' and nut that holds the oil pump in the block that Tom described. It is below the camshaft. The detailed instructions for removal and installation of the pump will be found about ten pages further on in the Shop Manual.

Let me know if this does not help.

I found the bolt and the jam nut and got that out, however like I said the body is in there to stay. CNC-Dude apparently has it right that it is a non serviceable part. Gona have the block and parts tanked and just thot maybe that part would come out also. But I guess not.

Most unusual - I've taken apart many 235s and 261s, even one that that had sat for over forty years, and have never had a pump body that did not come out fairly easily. It was certainly intended to be serviceable. However, it could be serviced still in the block, as CNC-Dude mentions. One of my 261s has a GMC oil pump. Based on the gear size, the GMC pump should pump about 10% more oil than a Chevy pump. Tom Langdon says that there is no real need for the extra pressure or volume, however. I'm using it just because of the link to the glory days of the Chevy six.

It might be different now, but years ago(20), only replacement gears were available for the pump.As there was no complete oil pump unit available to replace as a whole. Similar to a V8 Buick that has its oil pump built into the timing cover, and only gears to freshen the assembly. It was always my belief that the pump housing itself was permanently braded to the block, as was described earlier by the two round head attaching rivets or brads. Since I was familiar with other engines that had a non-serviceable pump, I never really questioned the removal of it. Other than having to drill the round head brads out, and replace them with bolts to reattach it to the block. Its been a while since I have really payed any attention to one. I've got a complete 216 to look at more closely.

Yes those two round heads are threaded on the inside. If you drill thru the center and use a reverse thread driver for removing stripped thread bolts they will come out. I've done this. Just don't snap off the head! Use low torque. I replaced mine with stainless allen head socket bolts.

3837004 is a 55-57 235.

Melling makes new pumps for our old inlines, and they can be bought from any good parts house, but you may find it cheaper through Patricks...

As for mounting, to remove the pump, you just remove the setscrew and unscrew the oil tube and give it a pull. If that won't do it, use a hammer and punch through where the dizzy goes. The part that the setscrew is mounted to, and is held onto the block by headless bolts THAT YOU AREN'T SUPPOSED TO REMOVE, isn't part of the oil pump. It isn't supposed to be removed because it is machined WITH the block, not separately. By removing it, you run the risk of screwing up the alignment between the oil pump and dizzy, with the possiblity of breaking the dizzy shaft, or trashing the gears.

I appreciate all the chatter. If I understand correctly the tube from the block to the gears will unscrew from the block part. All parts of this engine are in good enough shape to reuse. ie bearing etc. (However, I do plan to replace them) So I'm thinking I will leave that part in and reuse the gears and put it all back together. Or is that a cardinal sin in these parts?

If the clearances are good and the gears aren't pitted or scored, I don't know why you "can't" reuse the oil pump. In rebuilds past though I have replaced the pump in everything I've 'built' just on GP (but they were cheap at the time).

Didn't know that. After some new block machining it was reinstalled and all is well.

Good. Don't do it again...

Here is what I would do: remove the set screw and the lock bolt as Hoyt showed in the manual assembly. I would gently tap the complete oil pump out of the block so everything can be thoroughly cleaned. I would NOT drill out the studs from the outside of the block and take the chance of wrecking something. if you are patient and have all the lines off the pump and the lock bolt/jam nut off, it will come off. Its an easy process - just lube the thing and wiggle - it will come out.

Hey Nex, I am with you about the rebuilds. The next one I do for myself I am going to take my pump apart and take it to my buddy who is a precision machinist and ask him if they are serviceable. if so, I'm going to put new gaskets, spting etc inside and use it.

Heck, Smokey (and others) talked about blueprinting the pump. The big thing he suggested was to check the end clearance and machine (and lap) the housing till it had the correct (tighter) end clearance. He also suggested to lap the cover and put everything back without a gasket (yes check all the other clearences, he didn't say not to, he just put the emphasis on that as it was usually on the large side and was something you could do something about).

Admittedly he was using a SBC as an example at the time, though (should be the same principle regardless).