Honing vs Line boring

Jeff Rand

Well-Known Member
Sep 17, 2001
Had some problems with my recent rebuild on my stage 1. The #3 main bearing on the cap side showed copper after only a few hundred miles of use. The crank checked out ok but the main clearances on the block ranged from .0004" to .0008 out of spec.. (This block was already machined when I purchased it and the mains line honed)It was explained by my machinist that honing should not be used on the mains because it is difficult to control. He showed me that several of the caps had what looked like a cup appearence ( could see this effect where the assembled caps meet the block, it did not have a straight demarcation line) He prefered line boring which does not give the nice cross hatched pattern but can hold a tolerance across the mains of .0001". Also when he sets up for line boring, he positions the cutting tool to remove the majority of material from the caps.
Any thoughts or experiences?
He's right on with what my machinist has told me. Although it cost me more,
and I have to wait longer(My machinist likes to get 3 or 4 blocks lined up to
line bore before he does it. Alot more setup he tells me, hence the higher price
and the wait). It is the way to go in my opinion,FWIW. The gurus may see it
differently?? HTH.
Main caps

I doubt the fact the mains were "honed" vs bored had anything to do w/ the fact the caps don't fit the block. This fit is determined when the caps are cut prior to align hone/boring. Some shops use a cap grinder, others use a mill. [ruggles used a mill. Said it was more accurate.];)
The fact only 1 brg, think you said #3, shows the "copper", indicates it had improper clearance to begin with.
Next, I think most all the performance shops use the SUNNEN line hone and not a boring tool. Quicker to setup, less time consuming to complete.

If all the caps show this parting line problem, they were all cut wrong OR the "big bad detonator" has been there!!!:mad:
Is there any signs of fretting on either of the parting faces???

Back to sleep;) ;)