Oil pump intermediate shaft breaking

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One of the 2 that I snapped was a pinned Melling. I have checked for binding and there is none, brand new bushing. Still snapping
 
In addition to what has been said above, if it is snapping, make sure the pump is seated flush and the shaft is straight . If the shaft engagement to the pump is not straight, there will be excess stress applied to the shaft.

Also be sure there is the right clearance between the shaft and the bronze bushing as well as the mesh with the cam gear to avoid binding and excess heat build up for lack of clearance and oiling.

Also be sure the shaft length is correct. For example if the block and china wall has been machined, you may have to shim the distributed or shorten the distributor tang that engages the oil pump drive to be sure the engagement and mesh of the gears is correct.

See discussion in this recent thread starting at post #146.

 
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It's been argued that the pinned shafts are weaker than the pressed on and I can see some validity to it. The hole drilled through the shaft to accept the pin can certainly be a weak point.
 
It's been argued that the pinned shafts are weaker than the pressed on and I can see some validity to it. The hole drilled through the shaft to accept the pin can certainly be a weak point.
I did investigate this same thing years ago and it was said then that pinned shafts are weaker.
 
It's been argued that the pinned shafts are weaker than the pressed on and I can see some validity to it. The hole drilled through the shaft to accept the pin can certainly be a weak point.


If that’s where the failure is. Most of the failures I’ve seen the drive fractured at the neck down to the hex drive.
 
If that’s where the failure is. Most of the failures I’ve seen the drive fractured at the neck down to the hex drive.
I've seen that as well. That's why the "good" shafts don't have a hard "step" there. The goos ones look like this. Without the pin, of course. But you know that already.
INTERMEDIATE SHAFT.jpg
 
I did investigate this same thing years ago and it was said then that pinned shafts are weaker.


I should have asked RRR too (he can read this and answer too) how many of these failures have you seen at the drive gear end?

I know I’ve run as high as 125 pounds of oil pressure and never failed a drive.

I also gave a theory about bronze gear wear. IMO most of the bronze gear failures are because cam thrust is not verified and corrected.

If it’s not corrected the cam can move enough that rapid gear wear occurs.

I can’t count the number of times I’ve had to machine a cam gear to tighten up cam thrust. Almost half of the builds have the thrust too loose.
 
I should have asked RRR too (he can read this and answer too) how many of these failures have you seen at the drive gear end?

I know I’ve run as high as 125 pounds of oil pressure and never failed a drive.

I also gave a theory about bronze gear wear. IMO most of the bronze gear failures are because cam thrust is not verified and corrected.

If it’s not corrected the cam can move enough that rapid gear wear occurs.

I can’t count the number of times I’ve had to machine a cam gear to tighten up cam thrust. Almost half of the builds have the thrust too loose.
I've seen ONE break at the gear end where the pin is. It wasn't mine. It was on a big block. It had much the same shaft as the one I pictured above. That's the only one I've ever actually seen.
 
That is where both of my failures were, at the neck down where it goes to hex.


Does the drives you are using look like the one in post 12 or does it have a machined edge where it goes into the hex?

If it’s the latter that’s why it’s failing. Although I can’t think of a drive I’ve seen that was pinned and not machined with a radius going to the hex.

I was talking with a friend of mine who is older than me a bit and he said when guys were running straight 50 and 60 grade oils were spinning the gear on the shaft on cold starts when the weather dropped below 50 degrees.

Evidently that’s where the pinning came from. No one should be running oil like that today.
 
It looks exactly like the post in 12


Well damn. That’s a pretty thing. Maybe the new drives aren’t worth a crap.

Like I said earlier, I’ve run 125 psi on those drives and never failed one.

Unless some focknoid found its way into the pump and locked it up I’ve got nothing.
 
How much pressure is the pump putting out,,,,,unless it’s over a 100 pounds , you shouldn’t be able to break a shaft,,,not a good one .

Tommy
I h
Is this a fresh build, or a running engine.
You wouldn't believe the debris that'll come outta a used pickup while banging it on side of the solvent tank when cleaning .

A little background will help .
This is a fresh build, pick up is used but CLEANED through and through. New bushing, oil pump, etc.
 
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