352: Light Tic Under Light Load, At 2000-3000 RPM

Posted by Joe Hall On 2014/1/12 8:10:44

In recent thread about "Finicky" Packard V8s, I mentioned a noise in the 56J's motor that sounded like a wrist pin, on the driver's side. It began after I swapped heads, cam, lifters, and several rockers.
Before swapping the heads, I had checked valve spring pressure on the replacement heads, and they were all weak. So I compensated a little by spacing them to around 1.700" seated length. OEM is 1.750" and, doing the math, there should still be plenty of clearance when the valves are opened.

The heads were rebuilt 8-10 years ago by an experienced machinist, now deceased. He sleeved the valve guides, installed hardened exhaust seats, and replaced valves as needed. He had mentioned the weak springs, but I told him not to worry about them since I am not a hot-rodder. His work was always second to none.

Following the wrist pin notion I removed driver side head and oil pan, replaced #1 piston & rod (not needed), and six rod bearings (badly needed). I also checked crank end play. In retrospect. I really found nothing that "put a finger on" the source of the noise.

Today, the noise is still there, exactly as before. It does not sound like a lifter, but having ruled out the bottom end, that only leaves the valve train. It could be: a loose valve seat; valve sticking in the guide; spring bind; rocker sticking on the shaft; push rod; lifter, or cam profile. Presence under light load would seem to indicate the problem is toward the combustion chamber, i.e. loose seat, or valve sticking in guide, but I am tired of guessing. IN hind sight, I wish I'd disassembled & inspected that head when I last took it off.

At this point I am frustrated and refuse to turn another bolt till I can accurately diagnose the problem. Current plan, run it till it blows. My AAA is paid up, and I have plenty of motor parts. In over half a million miles, I have never had to have a Studebaker towed, but might be headed toward the first time.

It is most pronounced under light throttle in 1st and 2nd gear. It may be present at higher RPM and load, but other noises drown it out.