the machine shop that has the block says that my #2 main cap is screwed and that the original doesn't fit the register. I have got a couple other caps and he says that they won't work either. He said that I could line bore it but that it would probably cost quite a bit He says that if I can find a cap that fits the register we can line hone it. What should I do?bite the bullet
His statement to you sounds like garbage to me. IT is very unlikely that several different caps would all be over heated enough to shrink so they can't be made to fit the register. They get hot when a bearing spins or is trashed from a lack of lubrication and then they pull inward away from the register. Shops use used caps all the time to replace bad ones. If he can't I suggest to find a different shop.
Many times a blcok and caop can be saved by several different process. Some cps can be pressed in the center carefull on a press and opened up slightly and them the sides ground or milled to give a .005 interference fit on the register. If the cap has not pulled away fom the register much you can also ping the pan rails with a little chisel or center punch and bring the rails in slightly to get the register/cp interference fit. This is done in even sone of the biggest shops so it is not a home brew fix.
I will say that no matter which way you make a cap to work it will still need to be align honed. If you buy new caps it will need to be align bored.
Ed