Pulled the HEI out of the 454 today getting ready to put in the TBI. The shaft, just above the machined areas at the end (bottom) of the shaft is broken. Not cracked, completely broken. Any thoughts?

I went over and looked at the distributor and the new manifold - it floats in the hole, like the distributor needs some kind of spacer or something to fit correctly. This doesn't seem right...

Sounds like it needs a shim or two. Moroso makes a shim pack, plastic shims, for this problem. It can happen when you machine the deck or heads or both.

I always check the distributor fit to see if it floats above the intake. It puts a severe load on the pump shaft if you try to tighten the hold down to prevent the distributor from moving.

 

What I mean by "float" is the distributor seems to be too small for the hole in the intake - I can move it quite a bit while it is "seated" in there, and tightening the hold-down only forces it off to the side. As far as I know this block hasn't been machined, but you never know with chain store rebuilds (they don't even know). I'll be playing with the shims when I install the manifold, but it also seems like I need something to simulate a smaller opening in the intake as well.

 

I'd be looking inside the oil pump--and inside the oil filter--for debris. If you broke a 1/2" steel shaft, I'm thinking it took some force. And that force probably came from an oil pump locked up with debris between the gears.

Yeah, most aftermarket manifolds have oversize distributor holes. I don't know if that's a problem or not. Probably not.

 

I'd be looking inside the oil pump--and inside the oil filter--for debris. If you broke a 1/2" steel shaft, I'm thinking it took some force.

It's an aftermarket with aluminum shaft, but point taken...

 

Did you break the SHAFT or the HOUSING?

The shaft has the gear at the bottom, spins with the camshaft, and drives the oil pump. It is .480 for most GM distributors, and .500 for some aftermarket stuff. Plenty hefty either way. Nobody is going to build this shaft out of aluminum--or I want the name of the company so I can avoid them like plague, and taunt them mercilessly.

The housing is aluminum. (very early points-style units, or 'Vette tach drive distributors might be cast iron, but all HEIs are aluminum.) It just drops into the hole. If that broke, you've got problems I don't understand.

 

My bad - the housing broke (the part that doesn't spin). That's what has me questioning the alignment of the distributor in the hole. If the bottom is seated correctly but the top (at the manifold) is pushed off-center, I can see this putting enough angle on the housing to cause it to break...just guessing here...

 

In my younger days, I figured out that you can move an intake around quite a bit when installing it. To the point where the distributor just won't quite drop in the hole, and the top will hit the intake. If it's tight when dropping it in, that's probably what did it. I always drop in the distributor and adjust the intake to where the distributor is nice and happy before tightening the intake bolts.

 

Actually I dropped the distributor into the new intake (new to me, it's supposed to be the intake that the dist. came from) and it is quite loose in the hole. It's not even on the engine, so the bottom just dangles in the air...

 

Well, based on what I think I know it must be designed this way, because the flare on the distributor is way smaller than the hole in the intake, maybe because the intake floats around. I guess I need to make sure that my hold-down doesn't cause the dist. to move sideways in the hole...