OK, more progress- - - - -I machined some bronze bushings the right size for a press fit into the 292 connecting rods, to reduce the small end diameter to the size of the 235 wrist pins, then I pressed them in and honed them for a correct fit on the 235 pins. That Sunnen hone machine is earning its keep! Next I'll assemble the widened rod caps onto the 292 rods and recondition the big ends back to the right diameter and compensate for any distortion the TIG welding might have created. That's done by grinding a few thousandths off the rod and cap mating surfaces to reduce the size of the hole, then using the proper size mandrel and honing stone to make it round again. That procedure shortens the rod a tiny amount, but on a non-racing engine the difference isn't critical. On a round track engine, I'd go a couple of steps further- - - -measure the center-to-center distance on all the rods, find the shortest one, and recondition all the others until they were all exactly the same length. Then I'd check the deck clearance between the piston tops and the top of the block, and mill the block to get whatever deck height I wanted. I'll also use my triple-beam scale and a holding fixture to weight match both ends of each rod (with the bearing installed) to a tolerance of +/- 1/10 of a gram. (A dollar bill weighs almost exactly one gram). Ditto for the reciprocating assembly of pistons, wrist pins, rings , wrist pin thrust buttons, etc. That's done by weighing all the parts together, finding the lightest assembly, and machining the balancing boss on all the other pistons to get that 1/10 gram weight match. Since an inline six crankshaft is inherently balanced, all I'll need to do with the crank is spin it up to as fast as my lathe will turn to make sure there's no vibrations there. I can get the lathe cranked up to over 2K RPM, so getting a 100 LB. crankshaft spinning that fast sort of increases the "pucker factor" a little! It's surprising how smooth an engine with weight-matched parts will run, even without sophisticated spin balancing.
The "long stroke" engine with the NASCAR rods will get a similar procedure, with bushings being installed in the 235 pistons to accommodate the 21 MM diameter wrist pins.
Jerry
