Oil pump shaft on 302
 

What's up all... I have a technical question for anyone that can help. Here is the setup:

Edelbrock Performer EFI intake
E cam
MSD Billet distributor
Melling high volume oil pump
Stock oil pump shaft (2nd shaft was FMS hardened)

OK... I got the motor rebuilt about a year before I blew the first shaft. I was driving down I-4 and I saw my oil pressure gauge drop to 0. I towed it back to my shop, and had it checked out. We couldn't find anything... we cleaned out the old oil pump hopefully to find something that got stuck. All we found was that the shaft just snapped in two...

So I put new bearings and a new high volume pump, but this time I put a Ford Motorsport hardened shaft in there. About 20 miles after that was done, I blew ANOTHER shaft at about 5000 RPM... :?

I am stumped. I have no idea what would be causing this, and my car hasn't moved in over 6 months. Any help would be greatly appreciated.

-dave

Something is outta alignment. I would try a new pump first. I bet something got messed up on the inside and it wasnt spinning true anmore

Perhaps the first one failed due to fatigue and bent the pump drive slightly. There is NO REASON why the FMS one would fail within 20 miles.

Ummm... is there a reason for the high volume pump?

My understanding of the 302 oiling system is that the pumps are fixed volume pumps. The stock pump is sized to flow oil through the oil passages and be at X psi while doing so. By putting in a higher volume pump, without having a need for more oiling (larger oil passages/ very high rpm's) all you do is increase the pressure but not necessarilly how much oil actually moves.

The end result is that you are putting a lot more strain on the pump shaft because it's trying to pump oil into a highly pressurized area. Most of the reading I have done has frowned upon high volume pumps in stock applications for this reason.

Think like a tire pump. It moves the same volume of air everytime you push the plunger down. When the tire has little pressure, it's easy to push. When the tire has high pressure, it gets really hard to push. Same kind of principle.

I have always used stock oil pumps in 302's and I have never had a problem, I have also used fms hardened pump shafts without any problems. +1 on the above.

i am with leonard on this one. you can only put so much oil through said space....oil dosent compress well.

OK... well, i guess I will get a stock melling pump. Anyone suggest the ARP shaft? I hear it may be stronger than the FMS.

I broke a stock shaft. Burnt up the turbo as a result. That sucked. No problems yet with the FMS shaft. You pump is probably binding. You don't need the high volume pump.

ive got a friend that had a shaft break without a reason as well.., ((302)),,thats sucks, said their wasnt any evidence left behind, he was looking for something stuck but could not find anything.....

Allright... thanks for all of your help... I am trying this all over again today. Here goes another $600.

Let us know how you do.