Pinning Intermediate Shaft?

[Cranky]

So, is the argument - since you don't know the interference fit, you must pin it?

How about this - Have you seen any intermediate gear slip on a shaft? If so, which one and under what conditions?

Not sure I've ever heard of it happening. I always thought the hex at the bottom was the weak point - even on unpinned units. Who knows?

I've seen lots of broken shafts at the bottom and none at the top.....gofer it! And I've run lots of 'doctored' engines in my time....ie, thick oils and 3 cans of STP added on top of that!

 

[Daves69]

.........It's hardened........

If you're concerned about slippage, maybe you could mark it somehow for visual reference should an issue occur.

 

[gzig5]

I was advised by my builder, who's pretty well respected, to not bother with pinning the Melling unit I received. I'm pretty well setup with a milling machine and lathe ect., but if the shaft is decently hard up on the gear end you will need a carbide reamer once the hole is drilled. For a solid pin the hole should be reamed for proper surface finish and fit. To do it right and actually make the part better, it's more complicated than pushing an 1/8" drill through and hammering an oversized pin in place. Using poor technique, you can actually introduce stress in the shaft that could result in a fracture down the line. Cross drilling a shaft with a hole approximately half it's diameter doesn't do anything to increase the torsional strength of the shaft. I don't remember if we went with a HV pump or standard, but we were getting 70-80psi during the dyno and break-in runs. That is mostly attributed to good bearing clearances and the bushed lifters eliminating a bunch of oil leaks in the the valley. I probably would have preferred to have a pinned shaft, but like most, I've never heard of a gear spinning off, so I'll roll the dice.

 

[Ironmike]

Have you seen a quality unpinned unit slip?

Nope. But for me, it's peace of mind. I "overdo" everything a bit. Helps me sleep and my engines run long and hard.