The first thing to do is measure the crankshaft journal for diameter, taper, and out-of-round. If it's OK on all the rod journals, move on to checking the oil clearance. I prefer to use a piece of shim stock between the rod cap and the crankshaft, about half the size of a postage stamp. Insert a piece of .002" shim, torque the rod bolts, and try to rock the crankshaft a few degrees by grabbing the flywheel and pulling it back and forth. Don't force it to move, just give it a good grunt. If the crank turns freely, substitute a piece of .003" shim, etc., until you get a firm drag or a lockup. When the turning effort increases noticeably, you've found the clearance. Repeat for all six rods.
Om the oldtime reconditioned rods, we would coat the crank or the rod with Prussian Blue, and snug the rod against the crank. Turning the crank would reveal tight spots, evidenced by a bright scrape mark in the Babbit. A bearing scraper or a sharp pocketknife was used to scrape away bearing material until the rod exactly matched the shape of the crankshaft, evidenced by a smooth smear of bluing without bright marks, then shims were added to establish the proper oil clearance. Fitting babbit rods is fun!
Jerry
