400 SB Rear Main Cap - Team Camaro Tech
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post #1 of 4 (permalink) Old Mar 27th, 04, 07:31 AM Thread Starter
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I have a 400 short block, disassembled. I was looking at the main caps and the rear main seems to fit different.

The others need the pressure of the bolt to seat them into their notch. However, the rear drops right in. I did a crude check for side-to-side movement (without bolting it down) with a dial indicator and it is about 1/1000 inch.

Is this ok? Or, should it be basically press-fit like the others.

Hopefully I explained this so you understand my question.

Thanks!

1968, M20 PDB 12posi-3.73 400SB (KB125 5.7"r AFR195 CS286H 750cfm-mech-annular_boost 10.2CR AirGap 6AL)
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post #2 of 4 (permalink) Old Mar 27th, 04, 09:34 AM
 
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If your 400 block has been line honed/bored you will require felpro rear main seal #2909. That maybe the clearance issue you have with the main cap.
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post #3 of 4 (permalink) Old Mar 27th, 04, 11:11 AM
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Bill
 
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Location: Waldorf Md. USA
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Rogue,
Align honing has absolutely nothing to do with the problem you are having. If anything, when a block is align honed, if any of the caps are found to be loose, we usually tighten them up a bit by "peening" the block at the parting surface. If your cap really only has .001" play, it will should not be a problem, but you should have it checked before you go any further. If you have a good dial bore gauge, you can bolt the cap on and measure the bore where the main bearing fits. If it is within specs and round, it "should" be ok. If not, the block should be align honed, at which time your machinist can "tighten" the cap up. The most usual causes of caps becoming loose are probably detonation or a real bad out of balance condition. Either will make the caps try to move and eventually they will a bit.
If you do get the block align bored or honed, make sure to remember what Rascal said ... you have to use a special rear main sel.
If you are rebuilding the engine, your machine shop should be able to check it for you.
Hope this helps.

Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner


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post #4 of 4 (permalink) Old Mar 28th, 04, 07:07 PM Thread Starter
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Thanks for the helpful answers!

1968, M20 PDB 12posi-3.73 400SB (KB125 5.7"r AFR195 CS286H 750cfm-mech-annular_boost 10.2CR AirGap 6AL)
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