N62 Main Bearing Cap Fit

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   The main bearing caps on this little N62 don't seem to have any interference fit with the cylinder block. The caps are able to shift sideways on the 1/2 inch studs, because of the clearance holes in the caps.

The engine is at the machine shop and requires a line bore. The machinist doesn't feel comfortable because there seems to be no way to get the cap on off and back on in a repeatable manor.

Shouldn't there be an interference fit between the cap and the block? All other engines I've rebuilt have this. How would I install the cap and be sure it's centered? And be able to repeatably install the caps?

   Jim

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jange01 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 25 May 2014 Location: Sandown NH Points: 38	Post Options Post Reply Quote jange01 Report Post Thanks(0) Quote Reply Topic: N62 Main Bearing Cap Fit Posted: 17 Sep 2024 at 1:11pm
	The main bearing caps on this little N62 don't seem to have any interference fit with the cylinder block. The caps are able to shift sideways on the 1/2 inch studs, because of the clearance holes in the caps. The engine is at the machine shop and requires a line bore. The machinist doesn't feel comfortable because there seems to be no way to get the cap on off and back on in a repeatable manor. Shouldn't there be an interference fit between the cap and the block? All other engines I've rebuilt have this. How would I install the cap and be sure it's centered? And be able to repeatably install the caps? Jim

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PaulB Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 12 Sep 2009 Location: Rocky Ridge Md Points: 4753	Post Options Post Reply Quote PaulB Report Post Thanks(0) Quote Reply Posted: 17 Sep 2024 at 1:21pm
	As with the BE/CE engines, modern machine shops are not familiar with all of the idiosyncrasies of older design engines. There's nothing wrong with your block. When assembling your engine crankshaft with the correct bearings, snug things down, feel for any binding on the crank, tap the main caps back and froth until binding disappears, sung it a bit more, recheck for binding. Continue snugging and checking until proper main bearing torque is reached.
	If it was fun to pull in LOW gear, I could have a John Deere. Real pullers don't have speed limits. If you can't make it GO... make it SHINY

steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 81309	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 17 Sep 2024 at 1:56pm
	tell him to make a 2 inch long shaft that is .002 inch smaller than the bore.... set the shaft into the hole and snug down the bolts.. remove the shaft and bore the hole... do the final assembly with bearings as Paul said.
	Like them all, but love the "B"s.

jange01 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 25 May 2014 Location: Sandown NH Points: 38	Post Options Post Reply Quote jange01 Report Post Thanks(0) Quote Reply Posted: 17 Sep 2024 at 2:45pm
	Ok. Thanks The reason I see to need a line bore is because of clearances. Not sure what some one else may have done in years earlier. I was hired for a rebuild of the N62. I disassembled and sent the engine out for machining. The engine sat at the machine shop for months before finally being done. I brought it back to my shop for assembly, as usual. The crank was turned to .020 under, and measures correctly. The rods are .030 under, and pistons are .020 over. During assembly I determined with plasti-gauge that I had .005 -- & .006 main clearances. Rods clearances are fine. I sent the engine back to the machine shop to help figure out what was going on. The engine sat there for over 6 months with out being looked at. I finally pulled it and found another local, recommended shop. The new shop trying to measure the bore in the block, is having trouble depending where the cap tightens down. He figured probably end up shaving the caps and re- line boring. That's where we are now. I'll talk with him again On a side note, to bad about my previous shop. There were two partners, and I most;y dealt with the main man who for all intent and purposes ran the shop. Nice, smart, good ole boy, old timer. We did over 35 engines together. He retired and sold out to his partner, who while a good automotive machinist, apparently cannot schedule and may have now lost one of, if not his best, customer.