One thing I will add is when I use aluminum covers on them I use a split lock on the bolts and overly tighten them. I know I'm getting a little off topic. sorry.

It could be a shaft failure, too hardened.

Use a long hex rod to check the feel of the oil pump once it has been torqued onto the block. Sometimes the oil pump housing will distort and bind up the gears. In your case it should be fine since you had run it before, but who knows. Might have been a bit of extra resistance coupled with a weak shaft.

Kind of scary, that little hex tip is what keeps a $20,000 engine from eating itself.

It would be interesting to know what the hardness is. I bet there's a way to check it. Probably in my old Machinery handbook.

Awesome effort! Sorry, dumb question, but it looks like the hex end was too short? At least based on how that broken off part looks in that picture?

A better picture, for whatever it is worth. (Yea its broke and needs to be replaced)
I agree it is a strange looking break. More a brittle fracture than a malleable twist. But the tip should have some hardness, just not brittle.
And it was running after the break, so the ends may have touched, if the broken tip didn't fall farther into the pump recess. It doesn't look like they rubbed.

I will drain the oil pan into a clean plastic tub and look for any engine debris there.

Are you looking at the "Before/After" picture, or the picture with the measurements & specs?
I think it looks normal length.

I think you are mentioning a possible block error (like Al ) that the oil pump machined pad isn't perfectly aligned with the shaft/bushing in the block.
I have primed the engine many times in the past couple weeks with the oil pump bolted up and the drill "felt" normal turning the pump.

During mock up, did you install the oil pump drive and tighten down the distributor to check to make sure the oil pump shaft had some clearance? I have seen more than one that bottomed out into the gears.


Joe

I broke one when I changed a oil pump to a different brand the shaft was too long and I did not notice the distubuter was not seated all the way tighten it down when I started motor made noise found shaft broke because it was too long

I had one twist off on the engine after running it to warm the oil up on the dyno after 10 to 15 minutes, this was a new World iron block that had not been machined correctly on the oil pump mount pad, it had a tiny ring (.0003 to .0009 or so) that was sticking out around the oil pump drive hole but not enough to see or feel until using a straight edge across it trying to find out why it broke that shaft off while dyno testing that motor in Boise ,ID for a customer who lived and race there.
I had called my wife to have her bring me the last new one I had in stock back home in Bend and had her drive to Burns, OR (about halfway between Boise, ID and Bend)
The dyno operator found that ridge and had removed it by the time I got back and took it in to the shop the next morning
I hate Murphy

To be honest, the intermediate shaft looked too short on the computer I saw this on. Def didn't see any measurements & specs.

I do remember measuring this shaft after I bought it last year (April 2021). That is when I took the "Before" picture with the MP packaging. But I can't find a record of my measurement.
As I recall, it matched the spec length. I was checking to make sure it wasn't longer for certain other Milodon pumps.

Absolutely, looking at your oil pump the only way it could be too short is some type of manufacturing defect. Problem must be on my end, I missed where you measured and depending on what I view on, the broken piece looks short or “normal” sorry for the distraction and best of luck

That looks like bad metal to me Maybe when they forged it , it packed all the bad material in one spot
I've seen similar problems on other motor parts like a broken ring with a oval bubble in the material were it broke

I'm no metallurgist, but that break looks like bad material.

too much heat treat does that to good metal.

One time I made tapered collets for my magnetic sine vise. I made an oops on the heat treat (didn't read the instructions correctly). It broke when I dropped it to the floor - it was a really small piece.. It was rock hard with zero toughness. Brittle as all heck.

Wow Jim! The up-side, as has been said, is that it happened where it did. Sorry. This is going to be an impressive runner when it gets out though.

I drained the oil into a clean plastic tub. Then I filtered it with a cone shaped disposable paint filter. Zero debris or anything. So it is good to know no other hidden engine wear/damage.

I don't see any pump to drive hex problems. The depth of the hex hole in the oil pump is much deeper than the bronze gear oil pump drive shaft reaches. Hole depth 1.04", and the calculated insertion is only 0.863"

I will double check my measurements.

Wow, just seen this thread. Stinks you are having trouble Jim.....

I just put a new Milodon oil pump drive in mine last week so I am a bit worried now seeing this.

How much oil pressure are you running?