sbc oil pump shaft breaking

[r3tracing]

has anyone had any sbc oil pump shafts break one ear off the top of pump and one end of the oil pump shaft. we have one motor that has done this twice with two different pumps and driveshafts.

[perfconn]

If your block has been decked or the intake manifold has been cut then you could be bottoming out the distributor.

[Dirtrunner35]

Yes I have, I had a mellin break. I use arp now.

[parrot69777]

Never have seen it break anything as long as your using a steel sleeved shaft.

[r3tracing]

steel sleeved shaft both times. moroso shaft melling pump

[fast_crew]

Does the pump still spin freely after the shaft failure? Have the pumps been disassmbled and inspected for galling or possible signs of debris went through them. This would be the most likely casue for a shaft failure.

[Egoracing]

I agree with Perfconn, if there has been decking done and even if it has not, the distributor may be to long and is binding up the shaft into the pump. Take the gasket off of the Dist. housing and set it into the pump shaft and see if the distributor is up off of the intake. If it is and you clamp it down you are binding it up. You can get spacers to adjust it if needed for the pump drive end AND the distributor housing.

[r3tracing]

the motor continues running. this problem is only found at the end of the season during inspection for next year. both pumps were disassembled and found nothing unusual with them. this motor has a mag in it not a distributor. has anyone seen a mag do this like if the shaft was bent. we have not taken the mag apart yet. last winter we just thought it might be a bad shaft and now after running all summer it is broke again just like last year. the motor never does anything wierd like oil pressure problems or abnormal bearing wear. just a broken ear on the oil pump shaft.

[sj valley dave]

It doesn't matter if it is a distributor or a magneto. You can still be binding up the shaft. Try what Terry and Ego suggested. If you drop the mag into the intake with no gasket under it, does it fall flush against the manifold or is there a gap. If there is a gap you need to get some spacers to space it up as it is binding the shaft...

[r3tracing]

wiil check that, motor is getting machine work done then we will reassemble it.

[500BOMBER]

If your breakin' 1 ear on the pump gear shaft and 1 ear on the topend of the pump drive shaft........I'm thinkin' alignment.........maybe.
Also...If the distributor was being "jammed" into the pump. The pump would be "eatin" itself up quite quick, which would end up as a pressure problem. (speaking from experience)

[fast_crew]

Possible chatter from the mag causing excessive vibration in the pump shaft. I know a MSD mag is rather hard to turn past the magnets and you can hear them chattering or almost ratcheting at an idle.

[r3tracing]

that is a very interesting idea. is there a way to check the mag or a way to help solve the problem. this is a msd mag in a sprint car.

[fast_crew]

We run a 410 sprint but with a dry sump pump driven off the front of the cam. Something I would check is the fit between mag gear and cam gear at install, you may be able to run an oversize mag gear to eliminate any slop there that would add to the chatter, there are several sizes available, .006 is usually fine though, that may help. I would also try changing pump shaft brands maybe moroso has had some issues with theres.