Oil Pump Problem

My buddy has a 521 iron headed CJ motor. I did a freshen up on it last winter. It was a typical deal, new rings, bearings, gaskets, timing chain, oil pump, freshen heads, and a new forged Eagle crank to replace the cracked reground cast stroker crank. They re-installed the engine into the car, got it running and everything seemed great. The car actually ran the quickest it ever had after this rebuild, by over a tenth. After several races, they noticed that the oil pressure was acting funny. Only 40-50 psi at idle. It would build pressure when you revved it up. After a run it would fall to about 20 psi coming down the return road. Whent it cooled off it would come back to 40 or 50 psi. My buddies son is just in his scond season driving the car and hadn't been paying attention to the oil pressure, so we had no idea when the problem started.

So I get the engine back in the shop and disassembled, trying to figure out what is going on with this thing. All the bearing clearances were .003-.0035, but the bearings didn't look very good. I take the oil pump apart and this is what I found. Two of the ears broken off the bottom plate of the pump. I'm sure this was allowing pressure to bleed off instead of oiling the engine properly, and I'm guessing would have eventually broken the plate off of the pump. This is a FMS/Melling pump. I have never seen this happen before, and wanted to share so everyone could store this in their memory bank if you get some weird oiling problems.

Not sure,but they might have torqued the pump cap bolts too tight after/if they disasembled it. Just a guess of course.

That's a new one for me Never seen that condition before....wow.

Lem Evans wrote:That's a new one for me Never seen that condition before....wow.

LOL....Lem, that seems to be the story of my whole racing career

When I disassembled the pump, the bolts didn't seem overtightened. I just used a regular 7/16" box end wrench.

We've taken apart countless Melling oil pumps. One thing that has always astonished me is how loose those bolts are on the new pumps.

Tip: Always assume nothing is ready to go out of the box/always check out new componentry just as you would any used componentry. Familiarize yourself with and evaluate everything you use to build an engine.

Paul

p.s.: If you need a replacement gerotor cover for that pump, I'd be happy to send you one, just PM me your address.

Just realized I didn't offer any advice on evaluating the condition of the pump so as to determine what might have been the cause for such a failure in the first place. Like Lem (and probably everyone), I've never seen a solid iron gerotor cover break so there must have been a reason behind it...such as foreign debris getting lodged between one of the HV gerotor cover's cast-in oil cavities and the rotor vanes, for example. As far as evaluating:

• Inspect the machined side of the gerotor cover for signs of taking a hit from the inside of the pump (as described above in this post).
  
• Check the machined side of the gerotor cover for flatness (make sure it was not stessed by being bolted to the pump body)
  
• Check the pump body's machined surface (where the cover mounts) for flatness; be sure to check not only for high spots between cover mounting holes but also check that the mounting holes are not low spots on the pump body.
  
• Check that the gerotor mechanism is competely inside the pump body's gerotor cavity (with cover off) and not protruding above the pump body.
  
• Visually inspect the gerotor cover against another one to see if there is anything unusual about it dimensionally.
  

If everything checks out, then this must have been a fluke of some kind. But no-one can be sure without evaluating to some extent. If this were a 2Y 460 crank with a hurt journal, for example, we'd want to check all the mating parts just the same. Lastly, if you opt to just purchase a new pump or don't have the time to investigate the cause, send the pump here I'd be happy to look it over myself and tell you what I think.

Paul

Thanks for the info guys. The inside of the pump still looks brand new, and feels very smooth when turning it by hand. The machined surfaces still look perfect. I ran a straight edge across the surfaces and they seem to be OK, and the gerotor is flush with the cavity. I'm going to set it up and run a dial indicator across the bottom of the pump and gerotor to confirm flatness. You're right Paul, I should have inspected the pump before installation. I just spun it by hand and it felt nice and smooth. So I went ahead and bolted it onto the engine. I will be a little more careful next time around.

BigDave65 wrote:...I went ahead and bolted it onto the engine. I will be a little more careful next time around.

Don't beat yourself up, Dave! As far as I know, nobody's ever seen this before. Okay maybe the pump assembly was dropped on its head sometime during it's handling/shipping and had a hairline fracture. But in all seriousness stranger things have happened, such as 4340 crankshaft forgings breaking in low hp applilcations and entirely on their own/without any evidence of a culprit other than the crankshaft itself. As you've already noted earlier in this thread....sometimes....that's racin'.

Paul

My first thought was the oil pump shaft was too long and pushed the cover down when dizzy was installed, but then there would have been wear on the cover and gears, which there is not any. Could also be when it was assembled at factory, maybe the assembler was having a bad day and did not tightend down cover evenly??

racnrick wrote:My first thought was the oil pump shaft was too long and pushed the cover down when dizzy was installed, but then there would have been wear on the cover and gears, which there is not any. Could also be when it was assembled at factory, maybe the assembler was having a bad day and did not tightend down cover evenly??

Thats kind of what I was thinking, but the way the cover has to slide over the end of the shaft just to get it in place to bolt it down, I don't know if you could get it uneven enough to break the ears off.

I have seen that exact thing.
At that time it was caused by an overzealous person installing the distributor.
After the gear was meshing with the camshaft, the distributor was tightened against the pump shaft; when it was discovered that the distributor still wouldn't seat, they started over ... the damage had already been done.

rmcomprandy wrote:...After the gear was meshing with the camshaft, the distributor was tightened against the pump shaft....

Aaaaaah, yes. The distributor gear meshed with the cam gear but the oil pump's hex shaft has not yet been aligned with the female hex in the bottom of the distributor shaft. And instead of turning the crankshaft a few degrees (enables hex shaft to align with female hex--then distributor drops/seats into place), someone tried to force the distributor downward against its will (in your particular case)...which forces the entire drive system against the gerotor cover.

Nice, Randy. I ain't never seen that one before.

Paul

that could also be the cause of some pumps breaking at the block,in the "neck"area.IMO

rmcomprandy wrote:I have seen that exact thing.
At that time it was caused by an overzealous person installing the distributor.
After the gear was meshing with the camshaft, the distributor was tightened against the pump shaft; when it was discovered that the distributor still wouldn't seat, they started over ... the damage had already been done.

You may be on to something there Randy. That makes sense! Thanks

What about an ARP pump drive??? Sometimes they need trimming for clearance?? I had one that was tight had no endfloat