This is a subject that I only have limited experience with so I thought I'd see what I am not knowing about this stuff.

I have a box FULL of old Merc TBIV parts. I am finishing up my low budget 496's and I pulled out one of them and tried to instal. It would not seat into the oil pump shaft.

Pulled out another, wouldn't go. Some of them are really worn out, but I am trying to figure out why they won't install.

Pulled an MSD billet off the shelf and it installed like butter.

I noticed the inside of the gear is wider. Wondering wear I got a mis sized oil pump shaft from and why there are different sizes.

After looking at my merc stuff, I am ging to scrap them all and buy MSD for piece of mind, but hwat are these component problems??

I thought all this stuff was pretty compatible??

Any ideas, or anyone know what is going on??

Jeff,

The MSD's are .500" shaft dia. All Merc OEM units are either .427" or .491". Due to interchangeability it is necessary to determine which diameter you have on an individual basis with OEM's. We are currently utilizing a hardened steel gear, which is compatible with billet cores, due to the spotty supply of the multi piece billet cores.

Bob

Actualy, I pulled the shaft out. The end of it was slightly bent. Not sure how. Probably installed that way back when the engine was built as these were rebuilds. So there is nothing really wrong. Put a new shaft in it and everything is good now.

I was going to say the shaft dia has nothing to do with the gears meshing with the cam..just the gear to fit that shaft...glad you got it figured out..

I wasn't having any problems witht eh gear mesh, it was just fitting onto the oil pump shaft.

Glad it was minor. Now I just hope the pan sealed back up.