Packard Forum Index » V-8 (1955-56)

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.

C'mon, Joe, those pistons have 150,000 miles on them and the rod bearings 90,000. Is that finicky or just a reasonable life span?

With the pins loose, have you checked the width of the ring grooves. Chances are they're equally worn.

Problem is, you still don't seem to have definitively determined the cause of the noise.

Keep us informed of your progress.

jack vines

Hi Jack,
As mentioned above, the ring grooves are OK, as is wear on the piston skirt, and inside the cylinders. There is barely any ring groove at the top of any of the cylinders.

Based on the one I removed, I'd have no qualms re-using these pistons, with .003" OS pins.

I kinda like seeing how long the old stuff will last. Its easier to just re-new everything, and often just as cheap dollar-wise. But I'd rather go this route when feasible, since it can be a testament to the old iron.

At any rate, 90,000 miles on the rod bearings is sub-standard in my book. Since #7 & 8 are still OK, it points to oil circulation. I ran this motor with an OEM oil pump the first 75,000 of those miles, and only swapped the Olds pump in about 15,000 miles ago. I bet if the Olds pump had been installed from mile one, those bearings woulda faired better.

As for the original tick, I'm gonna bet the rod was bent. Will know in a month or so, since I plan on buttoning the motor back up in the next few days. When the weather clears up, the car will be back on the road. No need for a seasonal shutdown here in the mild climate of Kentucky.
Thanks,
Joe

I'll have to agree with JV on 90K mile wear/life expectancy of the bearings. Especialy on rods. For any engine at that.

The real question here is as to what caused the nick in the cylinder. CJECK THE.HEADS!!! Make sure a small portion of valve guide isnt broken off.

Also note that fig. 13 oil diagram in sm is incorrect. The Rear main oils directly out of the pump at about 2" above the bottom surface of block. Itdoes NOT oil from the rite longotudinal oil gallery as the book erroneosly shows.