I have a small block 400 bored .030 over witha scat rotating assembly and I had the block align bored and my main bearing to crankclearance is over three thousanths and I want to keep it at about 2 and I was wanting to know what main bearings I need, and I don't know how much was taken out during align boring.  Also when I bought my scat rotating assembly from L&R automotive the sent my sealed power plasma-moly ring kit and a extra set of oil tension rings( I think thats what they are called, the thin rings that go on bottom groove on top and bottomof spiral ring)  with my probe pistions, now I just want to make sure I am not suppose to try to squeeze all four of those rings on the bottom, meaning thin ring, spiral ring, thin ring and then thin ring again. I dont mean to sound slow but want to make sure I get this right.  Thiis is my first time going solo.

Thanks

hi, hopin' i can offer some help. if youre over.003 (dial bore gage, or plastigage?) clevite are offered in .001 undersize and oversize. one is bigger on the insidefor higher mile cranks and rebuilders poss lookin for a quick fix to tighten it up a little. the other is bigger on the outside helping with align bore issues. good luck.

Check with your piston manufacturer about that "extra" ring.  If you're using longer than stock rods your pistons may have the wwirst pin up into the oil control ring area and that "extra" ring is necessary to support the bottom oil scraper ring.  i.e. it's important and necessary- not a mistake.

Yeah that is what it was and I checked with the manufactuar and that is what I was told due to my 6 inch rod, just trying to double and triple check when you are not for sure.  

lI've done the same thing with my 350 .0030 over and align bore.  trying to install the correct bearing is tricky.   The centerline of the crank is now higher in the block, which shortens the deck height, and can cause your timing chain to be loose.  The blocks deck has also been cut down, which shortens the block height even more. Ending up with a positive piston installed height may become an issue, the piston being above the deck of the block, depending on the compression height of the piston, the rod length, and the stroke of the crank.  Be careful. 

lcamino2:
<P>lI've done the same thing with my 350 .0030 over and align bore.  trying to install the correct bearing is tricky.   The centerline of the crank is now higher in the block, which shortens the deck height, and can cause your timing chain to be loose.  The blocks deck has also been cut down, which shortens the block height even more. Ending up with a positive piston installed height may become an issue, the piston being above the deck of the block, depending on the compression height of the piston, the rod length, and the stroke of the crank.  Be careful.  </P>

At our shop when we line bore we don't take andy material out of the block and we finish with a line hone, UI line hone appox. .003 out which in a perfect world you are only moving the crank to cam center line .0015 not very much.

Now just having a block line bored is not really the correct way to true up the main line as most line boring machines can only do 2 sets of mains at a time and most blocks require 3 different set ups to finish the job as we just got one in the shop that was off on alignment and we had to line hone it to make it straight.

And a on GM cam tunnels they are no where near blue print from the factory as GM rough bores the cam tunnels and from there under size bearings are installed and the cam tunnel is bored to blue print with the cam bearings in place.

At our shop we are set up to blue print bore the cam tunnels and when we have checked them before we start we have found them up to .014 out of blue print