Oil Pump shaft broke

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daddio4048

daddio4048

Daddios72
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My car hasn't been cranked up in about 3 months so I decided to go crank it up & get to operating temp. Cranked the car up to let it warm up & noticed no oil pressure.
After testing sending unit, pulled distributor & pump shaft & found the tip broke off. Glad I wasn't driving it when this happened! I'm running a Melling M72HV pump. My oil pump shaft is stock. I've built a 340 before in the 80's with the same pump & stock gear & I ran the car hard & never had a problem. I'm taking the oil pan off & removing the oil pump & checking it out.Do you guys think I should just replace the pump & be on the safe side or is it just to much pressure on a stock pump shaft using a high volume pump.I'm ordering a new Mopar performance oil pump shaft & bigger pickup tube since I'll already have the oil pan off.I plan on taking one rod cap off & checking to make sure it didn't run dry. Thoughts?
 
No… I would jut take the current one apart and inspect / clean it .
Might want to blueprint it while its apart. Ie… clean up flashing, enlarge exit passage , polish rotors, check clearance on cover.
 
I guess it does happen....Although I would never have believed it. I was advised to buy the HD intermediate shaft for my 340, so I reluctantly did. I took an old shaft, put it a vise and cranked on it 'til it broke.......And it It took a lot of torque before it failed.
 
Could be something in the pump. I once bought a 78/9 Ford LTD II, 351W that was "dead" because the NYLON TIMING SPROCKET had deteriorated, and a piece(s) of the nylon had jammed the pump, BREAKING the cam gear. In other words it broke the cam itself. Scored up the crank. I bought a "rering" kit, had the crank turned, bought a reground cam and new pump, threw it together and drove it for about 4 years.

DO NOT USE OEM nylon timing sprockets.

This car was infamously dubbed the "Skud missle" which means "according to me," a "low flying, poorly guided missile"

This is the day I hauled it to the junk yard. Did not get much for it.

img062.jpg
 
67Dart273 said:
Could be something in the pump. I once bought a 78/9 Ford LTD II, 351W that was "dead" because the NYLON TIMING SPROCKET had deteriorated, and a piece(s) of the nylon had jammed the pump, BREAKING the cam gear. In other words it broke the cam itself. Scored up the crank. I bought a "rering" kit, had the crank turned, bought a reground cam and new pump, threw it together and drove it for about 4 years.

DO NOT USE OEM nylon timing sprockets.

This car was infamously dubbed the "Skud missle" which means "according to me," a "low flying, poorly guided missile"

This is the day I hauled it to the junk yard. Did not get much for it.

View attachment 1716023630
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That's where I'm at, sounds like debris got in there. Unless there is a serious mis-alignment issue where the pump is off-axis or not square fatiguing the shaft.
 
Well, after looking at the shaft; it looks like there was a bad spot in it. It was used when I installed it & there is no telling what kind of abuse it endured. The hex shaft piece that broke off had a lot of play going into the pump compared to the prime shaft I used to prime the motor. Ordered new Mopar performance shaft designed for high volume pumps
 
Ive pulled plenty of hex drives that were well worn to the point that the hex corners were very shiny 1/2 way across the flats and I even found one that was physically twisted a few degrees. I dont know what causes this but the designer that made the oil pump drive off 2 90 degree gears via the camshaft and a chain really had to think that one through!
 
Do you have the part #?
Are you going to check pump?
Thanks
daddio4048 said:
Well, after looking at the shaft; it looks like there was a bad spot in it. It was used when I installed it & there is no telling what kind of abuse it endured. The hex shaft piece that broke off had a lot of play going into the pump compared to the prime shaft I used to prime the motor. Ordered new Mopar performance shaft designed for high volume pumps
Click to expand...
 
If you don't use a hardened intermediate shaft with an HV pump you certainly can break the stock shaft. Why do you think they make hardened intermediate shafts?
 
Bewy said:
Why do you need a HV pump?
Click to expand...

Because it’s a Chrysler that has idiotic oil timing. You can’t get enough oil to the rockers soon enough without one, especially if you are running full groove main bearings and any half assed performance oriented Chrysler should have them.

I’ve been running HV oil pumps since 1980. Never failed a pump drive. And I only started using HD drives when I started shifting at 8k plus.

My street/strip junk still runs a standard pump drive.
 
There's more than one thread on here with with the stock shaft twisting off with a HV pump .
 
Hey, @CFD244, how far north in Ontario? My daughter lives just North of Toronto. We have been up there many times. We have been as far north as about Huntsville. Are you further north than that?
 
Are you sure it wasn't already broken from the last time it ran?
My oil pickup was packed with umbrella seals but I dought that would cause the shaft to break.
Weakest link, if you make it bullet proof what will break instead?
 
Replaced oil pump shaft with Chrome Molly Performance one. Found not metal shavings in oil filter.Oil pump was fine. Test pumped in bucket of oil with no issues. Put everything back together & she runs fine. Dodged a huge bullet because if I had been driving it I probably be rebuilding motor !
 
Every time I replace the oil pump no matter if it's a stock pump or not I always replace the oil pump drive, I consider it cheap insurance. If it's a hv or hp pump then I automatically get the HD oil pump drive.
 
This happened to me March 2022. Shaft broke off in the oil pump. Found the oil pump sized up. Took the pump apart no debris at all. Found the specs for the pump and checked with feeler gages. one spot was too tight. Got a hv pump, harden shaft, and also replaced the bushing for the shaft. Found the bushing was worn and that’s what was wobbling the shaft and put pressure on the pump (so I’m guessing). Got the special tool to seat it in, put everything new in it. Primed it, started it and also noticed my timing wasn’t jumping anymore.
 
I broke an intermediate shaft with a Ford 390 one time after putting a high volume oil pump in it and using the stock intermediate.
When I started building Mopar stuff as a teenager I did my homework and I talked to people so I have never suffered this personally with my Mopars ..because I have always run the hardened intermediate shaft w/the pinned gear... because all the old timers, and all the books I read before I started.. said ...you will either A. Twist the tip off... or B. spin the gear.
It's good to prepare
 
Back in the 80's I had two MP HD oil pump drives fail.... Put the stock part back in after the second one & never had another problem....
 
Crack cocaine was also prevalent in the 80's.
If we really have people here saying to use stock un pinned un hardened drives with HV pumps... then cool stories are now fact.
 
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