I lost oil pressure at the end of a run yesterday. I pulled the distributor and then the gear/shaft. It was sheared off at the bottom that goes into the oil pump. I pulled the pump and the shaft was shattered in pieces. The pump seems to spin OK so it doesn't appear that it locked up. I still need to take it apart to look inside. The gear was a Mopar Perf. one, not the stock one. Any suggestions on what happened.

Yeah. The Mopar Performance piece failed. Take the intake off and verify that the shaft isn't in a bind between the distributor and oil pump. If all is ok, get a Milodon shaft.

If he's running a flat tappet/iron gear, are the stock ones failure prone? How are the melling shafts?

I would have expected to have junk in the pump lock it up to cause that. Sheared, shattered, twisted - how it broke may indicate a heat treat problem. Not good. I would be looking at everything.

How many runs and years of use did you have on this unit?
I have twisted more than one of the Mopar Hi Po off with debris in the pump
It didn't break for no reason Maybe what broke it went up into the motor
Figure out what went wrong before proceeding and correct it

I still have to take the pump apart. It does spin freely when I took it out. Roller lifter, belt drive, 1st run on this motor, the pump is fairly old, we took it apart before assembly and cleaned it, the gear/shaft was brand new. The binding comment may have something to do with it. The gear/shaft went in a little harder than I'm use to. What could cause the binding?

Do you have a old stock oil pump drive unit? If so have the teeth removed from it and install it into your block with that pump and use a long handle screw driver to rotate the pump counter clockwise to check for binding
Is this a internal pick up oil system oil system or external pickup system? If you are you using the stock pump with the stock cover it shouldn't matter how it spins in the block compared to out of the motor, but if you don't check it both ways you won't know if it does have a problem installed in the block or not
I built a bracket race motor several years ago with a new cast iron 4.500 bore World block and a Milidon dual line external oil system that worked fine on the engine stand when priming and checking, worked fine for 30 minutes on the engine dyno and then twisted the new Milidon shaft off in the pump rotor Luckily it was running under 2500 RPM warming up after lunch so no damage was done to it That dang block had a .003 machining ridge on the oil pump mounting boss that ended binding that cast aluminum Milidon oil pump body enough to bind and twist off that shaft when warmed up the second time
Good luck on your deal, let us know what you had to do to fix it

Not good. I would be looking at everything.

X2

Yeah, only time I have seen them break.

Ditto,I did that one time only!

Thanks for the help guys. It's an external PU. with a milodon pump. The pickup has a front and back PU. The block is a 400 cast block, 512, that I had replaced the same. Pretty much everything was replaced, except the pump. I will take apart the pump later, but as I said, it seem to spin freely. I'll drop the pan as well to check.

Again, thanks for the help.

On a side note, with the quality/fitment issue resolved, install the pump with the bolts lightly snugged then drop in the intergear then torque the pump bolts the rest of the way for a dead on hex alignment. EDIT with the pump out confirm the intergear turns free, one of mine had interference on the intergear cross pin to the bushing, it was driven down a bit too far.

Is your Milidon pump the cast aluminum or the billet aluminum one? Both of them now use three O rings on them to seal between the block and pump, are you using a gasket also? If so, don't
How much torque are you using on the four 3/8 inch pump retaining bolts?
The shaft broke for a valid reason, figuring out what caused it is the hard part, huh Dang Murphy anyways
Good luck, let us know what you find, that will help others in the future

Something small and hard has made it's way into that pump.
A needle roller from a rocker was the cause of my last fail, I now have a -12 filter before (external feed line) the pump and don't use needle roller type rockers.

Now clue why but I snapped a oem shaft off a 440 in my 4x4 just by hitting a deep pothole, simply replaced the shaft and never happened again....never figured out why it happened.

I took the pump apart, a couple scratches, nothing major. Nothing in the filter, nothing in the pan, all clean. I did not use a gasket. The pump is an older cast one. I have a Titan on another motor, I'll use that one. There were no marks at all on the brass gear, very clean. Could it of been from 1) Just a junk part, bad metal? 2) Could the alignment problem with the shaft (too long by mistake, or the shaft just wrong)?