78 gmc with 454 & turbo 400 breaking starter nosecones

Shims/clearance...

The front (rear of starter, but facing the front of the truck) starter mount missing?

yeah - the shims - wich are thin pieces of metal that go between the starter and where the starter mounts to the block - they come in different thicknesses - it is a trail and error kind of thing as to how close or near it needs to be.

Good luck.

-W

p.s. some sites to check out:

It is a lot of things, but trial and error is not one. There is a procedure to measure gear tooth clearance, compute the shims needed, and then you get it right. Guessing gets you broken starters, stripped flywheels/flexplates, and other nasty things.

starter

I agree, the starter nose it to close to flywheel. You need to shim it about 20 to 30 thousands to begin with.

stripped

Not really, you can tell by listening to it if it is too tight and if it was much over .030 interferance fit the starte would likely grind when engaging. This was fairly common on some GM engine in late 60?s thriugh mid 70?s or so. I have never seen one shimed more than .030 and usually around .015 to.020 at most.

Maybe you can tell by listening. Maybe I can tell by listening. But that doesn't mean the poster can tell, and judging from the post I'd say not.