[Will]

HIS - does .0015" - .002" in concentricity seem insignificant to you?

My 455 block ('70 YH 455, 2-bolt) is only .035" over and that's how much difference the torque plate makes.

Measure with torque plate in place after honing, bore is round. Remove torque plate (but mains still in place) and measure again, bore goes as much as .001" wider in one direction and .001" narrower in the other, mostly near the top of the bore.

Install head and measure again from bottom of block. bore goes back to nearly round, with only about .0005" or so out of round.

Done this twice now, I'm satisfied it's well worth the slight extra cost on a performance rebuild. After all, cylinder sealing = power.

Agree that Chevies are worse. Just tore down a low-mile 327 with blowby problems. Cylinders had 5 vertical polished "columns" in between areas were original crosshatch pattern was still visible. Polished columns were between the head bolts.

-Will