im in the process of rebuilding my 96 z and the other day when i talked to my machine shop i was told i couldnt turn or polish my crank in the one peice main block cause they wont hold oil pressure long they said i would need to go knew ive never herd of such bs but im new to the lt1 so fig id get some input i am gona put nitrous to the car also?? if anyone can help me out thanks!!!!

 

Sounds like BS to me.

 

well, what there talking about is the tension on the rear main seal. if you make the rear main journal .010 smaller diam,, it'll put less press on the lip seal. thats his point. you can do it, but he thinks it'll be a leaker. and I agree somewhat. dont think they make undersized seals.

I KNOW people have turned there LT1 cranks though.

 

I just rebuilt my 96 6-ish months ago...

I had 150K on it and all I wanted to do was to slap on a pair of 1-7/8 Hooker LT I picked up cheap... Popped three bolts on the driver’s side head and everyone said that I should use that opportunity to rebuild her.

When I opened that LT-1 up, it was the first time in my 48 years that I had actually looked inside a I/C engine; to say I was scared ****-less is an understatement.

Now I tell you that so you'll know I'm not representing myself as a Guru... just a guy that studied every facet of our common motor for an agonizing 4 months and worked my butt off to do as meticulous a job as possible, in rebuilding her. Here's what I found with regard to your question:

I suppose the question becomes how much polishing you wanted and why?

If you've major wear, I'd be hesitant to try and polish it; this for the same reason noted by another member, above; the tolerance of the journal/bearing... I don't know jack about these things, but it serves reason to me that one would have a distinct threshold on the journal size, required to reliably survive the stress of just being a crank... and that if one 'polishes' down below that threshold; that it isn't even a close call... who wants to gamble on that nightmare? Beyond that, assuming for the sake of argument that it is reasonable to polish to a point, that the thickness of the replacement bearing would need to be thicker... which may or may not be a viable notion; just a point of reason.

If I had had any serious wear in or on my internals, this would have immediately begun the longer, but enviable journey towards the 383 or 396 stroker... but barring that, I'd have bought a new crank.

 

well there's no worry with the undersize bearings, say -.010" or -.020". just would be skeptical of the rear main seal. its just a piece of rubber thats bent over sorta to drag on the crank to keep the oil in. if you make that sealing surface smaller, it'll lose some tension on the sealing lip and could leak.

 

There is no kind of "seal saver" kinda deal for a rear main with a one piece seal? I dont see where there would enough wear to make this an issue. Even if you did polish it. .003 or .004 aint gonna hurt it. Which is all polishing will take off.

How deep could the groove be from a rubber seal?

If memory serves, on a one piece rear main crank you dont turn the part the seal goes on....it hangs out the back of the block. Does not have a main bearing surface. Its only for the rear main seal and the flywheel bolts.

 

I don't see why they would turn it. I was looking at mine today as it sits on the engine stand. Fastboy, I agree, all that surface appears to do is let the seal ride on it.
OP, if you want some pics I can post tomorrow when I pull the seal off to replace it.

 

Actually they do make a sleeve if the area is grooved bad enough to dictate usage. But when they turn the crank they normally dont mess with that. USually they touch it with the polisher and leave it alone. but if it is grooved real bad then it may be an issue. since i cant see your crank. I cant say for certain

 

it is BS. You have a PM.

 

If the seal area has a groove in it from A LOT of miles, then you use a seal with an offset lip so it rides on an area with no groove. They also do make a seal saver, but it had better be put on exactly right or it will leak like crazy because it will be crooked.

 

I've never heard of polishing the Flange, I've always had my Journals polished, even when I built my LT1..

 

find a new machineshop.
Kory