Crank main bearing crush/fit question.

[69427]

It's my understanding that the main and rod bearings crush a little when the caps are torqued down. How many times is that crush fit good for? I'm just not happy with the rear main seal RTV sealing, so I'm going to re-do that. Do the bearings retain the tension if they're retorqued, or will they be a little "loose"? I just don't want to always worry about the possibility of a spun bearing.

Thanks,
Mike

 

[mrvette]

I have had caps on and off many times with new and well worn engines, never an issue, rods/mains/rear main...replaced rear main 'rope seals' never been a issue...

:sweat:

Oh, what do you mean about rear main RTV sealing?? two piece early block or a later '87+ one piece rear main seal??

or do they make a two piece crescent shape wire reinforced neoprene seal for a SBC/BBC like the old 500 caddy seal, that I used on my Poncho 455?? IF so, you need mike that seal really good, as they need fitted together under maybe 3 mills of tension on the end gaps....any more than that and it opens the seal around the crank and you got a HELL of a leak.....

don't ask how I know that....UMMM???

 

[Twin_Turbo]

The crush is a 1 shot deal, it'll crush once and not anymore.
The crush is designed into the bearing shells, with fresh ones you can actually see it. Put one in a cap, bore, rod fork or rod cap and you'll see they stick out.

The bearings aren't equally thick all way round. Near the parting section they thin down so that the bearing once crushed down't distort inward too much and reduces clearance.

The bearing will actually bite into the coarse honed pattern of the main bore (same for rod big bore) and this gives the bearing bite to keep it from spinning (increase contact area).

If you pull it apart, just don't remove the bearing shell and you have nothing to worry about. Also, the last thing you want is oil between the bearing and the block/cap.

 

[69427]

Thanks for the info, guys. I had sent an e-mail to Clevite's techline, but haven't heard back from them yet.

 

[TimAT]

Use an Anerobic sealer on the cap- I found a couple of sheets from GM- I thought I had scanned them but these pictures will have to do. Buff the cap real nice and clean, apply the sealer and bolt it on.