Packard V8s Can Be Finicky, & One Thing Often Leads To Another

Posted by Joe Hall On 2014/1/4 21:25:19

At about 200 miles on a recent heads' swap on the 56J motor a light tick began, at 2000-2500 RPM, under light load, most likely on #1 cylinder. After another 250 miles it was only getting worse, so I tore it down again.

I recalled stuffing about 6' of 1/4" rope through the spark plug hole in #1, to lock the motor in order to loosen the crank dampener bolt. So I hypothesized a broken piston or wrist pin lock ring. The motor has .030" OS pistons, so in preparation I bought an NOS .030" BonaLite piston from MM.

Upon tear down, the piston & lock ring look OK, but a light scar (barely catches the fingernail)is in the cylinder wall, that lines up with the lower edge of the wrist pin. With piston & pin intact, I cannot determine the source of that scar, but know it was not there when I swapped the heads. I now can only guess the rod may be bent, and causing the pin to shift back and forth slightly with each revolution. At any rate, I went ahead and swapped that piston & rod out.

When removing the piston, I found the rod bearing worn into the brass. I checked the others, and #1 thru #6 were the same, with only #7 & 8 still OK. The mains are all still OK, which seems odd, since every other Packard V8 I've torn down, the rods & 3 middle mains wore out together. (This motor has a little over 90,000 miles on last rebuild.)

With #1 piston removed, the pin free-floated back & forth in the piston and rod. In replacing the the other pistons' rod bearings, I discovered the pins all flopped back and forth.

The pistons have at least 150,000 miles on them, and were initially installed during a rebuild in the late 1960s. I re-used them for the last rebuild. They are not BonaLites, but look near identical to them. Other than the pin holes, they are still very serviceable, i.e. ring grooves OK. If I could find a set of .003" OS pins, I'd probably re-use them for the next short block build.

I have enough 352 stuff to assemble 2 good motors, but prefer to keep the original motor in this car if practical.

Either way, looks like I need to plan on a short block in the next 10,000-20,000 miles. Meanwhile will not plan on any long trips.