Checking rod/piston for squareness?

[ryan68bug]

Here's one to throw out there. I've got the Antique Briggs service/repair manual and was perusing the section on checking the rod and piston for squareness. Given that these tools are now obsolete, what are other folks doing in verifying this tolerance? Just curious, as I'm not sure what the odds are of an engine sustaining enough torsional twist to necessitate straightening the rod/piston alignment.

[George Andreasen]

If you have access to a lathe, try this: remove the piston and pin from the rod. Find or machine two pieces of cold rolled steel, one for the wrist pin and one for the crank end. Make them about 12" long, center drill each end in the lathe and fit them into the rod. Should be a close fit. Now lay the whole thing down on the lathe bed so the steel rods are across the ways and the rod is facing lengthways (along the bed axis). Since the bed is (or should be) pretty level and square, both pieces of steel should rest evenly on the ways. To check for square the other way, measure the distance with calipers from each center drill mark...distance should be the same on both sides. This will reveal any twist or distortion and can be corrected by muscle power in a bench vise. Be careful! Even a hefty looking rod is easy to move a few thousandths to bring it into truth.

[Kansas_Farmer]

I'd suggest the use of 1 2 3 blocks for this and not laying the test bar directly on the ways.