I have read a lot about aluminum blocks and push rod settings and how much blocks grow but don't seem to recall if lifter bores are affected. I have a World Products Hemi block with bushed lifter bores. Just wondering what the proper tolerance would be.

I set mine at .0010" to .0013" that's what my machine shop recommended.

The bushing grows less than the aluminum, so I worry more about the bushing getting loose than tolerance on the tappet. As always seems to be the case, I like wider better than tight. .0015 at the tightest, and normally .002 for me, especially with a bushing.

Darren, did your KB blocks have non-bushed lifter bores? If so, how well did they hold up with the miles/hours of a street car?

Have them both ways. I really prefer the bushed bores for oil control, but like I said earlier when the block gets hot, you're loosing some of your press fit with the bushings. I've been lucky so far and never had any move, but I have seen blocks where they did. Some shops will mill a half groove in the bushing and then once installed drill along side the bushing and put a roll pin in.

As far as wear, the bare aluminum bores get so much oil I've had no issues as yet. Ampco bushings are near indestructible.