New distributor drive shaft won't fit pump-why?

[69chargerrt]

Ok got a question on the distributor drive shaft to oil pump- I was replacing my distributor drive shaft and I found out that my new Melling DD shaft won't fit the replacement Melling oil pump that I used when I rebuilt the engine. It's slightly too large to mate with the oil pump drive. It seems to be exactly the same size (or very close) as the original drive, it just won't slip in like the old drive did (and I'd rather not try forcing it)

Has anyone had this problem? As far as the guys at the auto parts store can tell, while there are different varieties of oil pumps (hi pressure, hi volume, stock) the one DD shaft SHOULD fit them all. So I've got another drive on order just to see if this one drive was just not machined correctly- but if this replacement has the same problem I'm not sure what to do.... 

Thanks!
David

[FLG]

Hmm...

I have a melling pump and use the mopar perf shaft with no issues 

[69chargerrt]

Hmm- I may have to switch to the MP shaft if this replacement doesn't fit.   But I've heard that MP has had their share of mfg defects, too- I take it you haven't seen any issues with yours?

[John_Kunkel]

Is the point of interference the hex end or the where the round shaft enters the block bushing?

[69chargerrt]

Is the point of interference the hex end or the where the round shaft enters the block bushing?

It's the hex end.   It just will not engage the pump no matter which way I try to insert the hex end.   At first I thought maybe the hex end was 'keyed' so it could only engage the pump in one position but the FSM makes no mention of this...

[xpbprox]

It's not keyed, make sure its lubbed up. You could try taking the pump off and try putting it in so you can see where the issue is

[471_Magnum]

Had this issue on the small block I just built. Ended up removing an reinstalling the oil pump. Dropped right in then. Pump just wasn't quite bolted up square.

[tan top]

silly question  , there has not been a lot of oil run in to the pump drive socket has there  ??   & trying to put the shaft in is causing an hydraulic lock  

[69chargerrt]

silly question  , there has not been a lot of oil run in to the pump drive socket has there  ??   & trying to put the shaft in is causing an hydraulic lock  

Well I've got both the new drive and the original pump out of the engine- so I can eliminate any misalignments right there.   And I've opened up the oil pump, cleaned it and reassembled it- it turns freely by hand so I think that eliminates hydraulic lock.

When I first encountered this problem,  I noticed that the drive shaft would not drop in all the way.   I then removed the oil pump and the shaft would drop into position just fine.   It's when I pulled the shaft out and tried to just fit the two parts together by hand is when I realized that the hex end of the drive shaft would not drop down into the oil pump.

And, my bad here but I didn't say what this was for- it's a '69 Charger with a 383 engine....

[69rtse4spd]

 Try leaving your pump bolts a little lose, install drive shaft then tighten oil pump bolts. Could the cam & drive gears not be meshing right.  .

[John_Kunkel]

It's when I pulled the shaft out and tried to just fit the two parts together by hand is when I realized that the hex end of the drive shaft would not drop down into the oil pump.

If the hex end won't fit in the pump when both parts are out of the motor, something's machined wrong.

If the old drive shaft fits the pump but the new one doesn't, the drive is machined wrong (got mic?)...if a replacement does the same it's time for a little "massaging" of the hex or a different brand.

[Richard Cranium]

This will do the trick.........

[69chargerrt]

It's when I pulled the shaft out and tried to just fit the two parts together by hand is when I realized that the hex end of the drive shaft would not drop down into the oil pump.

If the hex end won't fit in the pump when both parts are out of the motor, something's machined wrong.

If the old drive shaft fits the pump but the new one doesn't, the drive is machined wrong (got mic?)...if a replacement does the same it's time for a little "massaging" of the hex or a different brand.

Just to let everyone know- I just got the new one, and it fits the pump just fine.  Must've gotten one made on a Friday afternoon 

Thanks!