Reply to "Boring 351C"

Usually not economical to hone more than about 0.004" (0.001" or .002" is usual), because of the time & labor invested- honing is slow. It's also easy to build a taper into a deep-honed cylinder if you're doing it by hand. And more than about 0.004" removed by any means usually calls for new forged pistons (2618 alloy which expands more with heat).

So if you have a cylinder or two that has more problems than 0.004" can fix, you should have your shop bore the engine, or find a different block. And if you bore, you should first sonic-check the cylinder wall thicknesses- many shops can offset the boring machine to partially compensate for a cylinder that is thin on one side. Std gaskets will allow this slight misalignment with no problems.

If bored, you will then need new pistons and today, custom sizes are available for not much extra. You are NOT stuck with the usual std or 0.030"-over off-the-shelf pistons; either cast-hypoeutectic or forged can be made. This can be a lifesaver for scarce 351-C thin-wall blocks.

If you have more time than money and are doing the engine yourself sort of as a hobby, you can hone out more than 0.004" but it will take days to do eight cylinders. I also suggest sonic-checking the cylinder walls just for your own information, even though with hand-honing you will not be able to compensate.

You are right on mentioning the torque plate; many years ago, I wrote an article on how much a typical thin-wall 351-C changes bore measurements with and without a plate torqued on. Before honing or boring, I suggest adding a torque plate and re-checking for cylinder problems. On several cylinders in the article, the bore changed in one direction, while one cylinder changed the opposite way. The biggest change was around 0.002". So if your block was prepped WITH a torque plate and its bores are later checked without it, the block may show distortions or ovality that will disappear once the heads are torqued on.

As an added note, precision engine builders are now using torque plates on iron 351-C CYLINDER HEADS before doing a valve job. OEM cylinder heads were cast thin-wall, too....