Hello, well I am trying to rebuild my b18 after blowing 2 craigslist motors. I have 4 blocks (2 the mains and rods are shot)... anyways when I took apart the first 2 bottom ends I never matched the main caps with the blocks... so now I have a bunch of main caps... Can I pick the ones that look the best condition and mix and match them? I was thinking I could use a bore gauge to measure the mains after they are tourqed down with no crank to make sure I am round... Is this okay or am I better off looking for a new block?

 

Swapping main caps from the original ones REQUIRES a fresh line hone of the main journal bores. Usually, the color of the block's internal surfaces is a good indicator of which caps go with which block... however, if you still feel like you are "guessing" on which go where... pony up the dough for the machine work or find a virgin block... WITH MAIN CAPS.

 

this. 100% this