Oil Pump Shaft
 

Thought I would share a picture of my new oil pump driveshaft that came out of my 428. It is a Melling pump shaft. I just got the engine running the first of April. The first start went well and the engine had plenty of oil pressure and everything was quiet. I drove the car around the block for the first test ride and it went well. I decided to work on the air mixture some on my carb to dial things in better and the car was sitting there idling in my shop. I heard a loud knocking noise, and I immediately killed the engine. Oil pressure was at 0 for about 5 seconds I would estimate. I decided to pull my distributor to check things out as the noise seemed to be coming from the back of the engine. I stuck a screwdriver down the distributor hole to check the pump driveshaft and could turn it about 1/4 of a turn without it even moving the oil pump rotors. So, I pulled the oil pan to find this. I removed and disassembled the oil pump and it was spotless. I didn't see anything in the oil pan that could have went through the oil pickup screen to lock the pump. The pickup screen was spotless. The oil filter was also spotless. The pump still spun fine. The new driveshaft was very slightly taller than the original one and I did not notice that when I assembled the engine. I didn't notice the distributor not sitting flush on the block when it was installed but I am thinking that when I put the distributor hold down clamp on, it must have put the driveshaft in a bind. That or the new driveshaft was simply not heat treated well.

Good news is that the car is running again and the engine was not hurt by this.

Good deal. Now, off to Vegas.:);)

I had the tabs broke on a stock shaft, cost me a motor block was junk.

Strange the way it failed. I had a freshly rebuilt SBC with a chattering noise coming from the oil pump. The pump driveshaft was a little too long combined with a thin distributor gasket. I put in a thick distributor gasket and it fixed it. luckily mine wasn't in enough bind to seize or break anything. You got lucky there also!

One more item to check when assembling an engine!!!

Count your blessings….You were lucky.

Was that a hardened shaft like the Melling 54A?

soft metal twists and bends that shaft looks like it splintered.

USUALLY a soft shaft will twist like a candy cane

Yes, this was a Melling 54A.

I thought someone (cannot recall who right now) was making an oil pump shaft with the tangs "enclosed. / encircled" Like the picture attached (that is Butler's priming tool).

It could have been made defective with not enough depth to accept the center round pin on the pumps drive shaft, especially since you state it was longer then your old one.

Not the first time Ive seen that with a pontiac

This one perhaps? made by Nitemare Performance Products:

http://nitemareperformance.com/pumpshaft.html

It appears that they test for hardness after manufacturing specifying 28-32 Rockwell hardness. Those are the same hardness specs that were used to determine if the Pontiac OEM SD rods were within hardness specs.

I've also taken apart a couple race engines that the tangs were starting to spread, although I never saw one splinter up the center of the shaft as the OP's has.

They also make one for IA block. I like the clip that comes on the end, the one that came with my IA block didn’t come with anything, when test fitting IA one with the distributor, ever time I pul distributor up, the shaft would come up off the pump. Can you imagine what a nightmare that would’ve been, after motor in car, and down the road having to pull the distributor only to have the shaft fall down in the motor. The one from nightmare fit perfect and has that clip so that can’t happen.

Although may not be relevant, but a concern I've had when running 20/50 oils in colder climates.

Same here. I had one twist like a pretzel years ago. H-O stood behind it and sent me a new one.

The picture of the split one is exactly the same as one that failed on me the first start up of my 469 build. That was also a Melling shaft. You could see signs on mine where the crank counter weight had touched it.

Those are nice pump shafts, I bought one.
But you can twist any shaft with thick oil and cold weather. Know of one twisted, thick oil, cold weather did it. Engine lived though.

You are lucky it didn't take out the block. Mine did. A rare WS block too.

Something that is never talked about is Distributor shaft end play.