Packard Forum Index » Post-War (1946-54)

Pgh Ultramatic wrote:
My best guess is that it's piston slap from a cracked piston skirt that was not distinguishable above the previous valve noise.

The fact that it occurs once per piston stroke means that it can't conceivably be in the valve train, unlikely also since the valve train was just redone.

It could also be a rod bearing knock but it's unlikely to "just have one" be problematic compared to a cracked piston.

Damaged pistons are not unheard of in high mileage engines, not just from overall fatigue, but also from detonation ultimately caused either by carbon buildup altering the compression ratio, or the timing/mixture drifting out of specific from lack of regular maintenance. Likewise if the engine was parked for a long time, some goofy things can happen with the piston or two with exhaust valves left open; the cylinders may flash rust over time, causing broken piston rings and/or excessive wear when the engine is restarted. Excessive carbon buildup can help to damage rings as well when restarting a dormant engine.

Pgh Ultramatic wrote:
One would assume it would change under those circumstances, but he already said that the noise takes 20 or 30 sec. to appear. Cold oil is much more viscous than warm so it makes sense it would quiet the sound.

Kunzea can you get 2 more recordings?
- wire off plug
- plug out

Each with the engine running long enough that the sound would be expected to appear.

kunzea wrote:
The following is to the best of my recollection.

Post-reassembly: Wouldn't start. No accelerator pump stream. Carb input clogged by mud dauber.
Cleaned input.

Warm adjusted valves while running. Sounded relatively quiet.

Temp ran high when adjusting valves: Temp went close to max. Infrared showed about 190 at sensor.

Better temp before driving but went close to max on short (< 1 mile) trip.

Change to lower temp (160) thermostat. Had installed new thermostat and new housing.

Re-torqued head.

Car shut off on short trip. Thought it was out of gas since no accelerator pump stream. Did start.

Fuel pump stream weak. Replaced filter. Could not blow into carb inlet barb. Removed and opened carb. Bowl was full. Turned out to be clog at accelerator pump check ball.

Sometime around here I rebuilt the carb. Auto choke wouldn't self adjust correctly. Realized I had old gasket on wrong side of metal plate. Auto choke still wouldn't self adjust correctly. Thinking this affected temp and valve noises. Retrieved new, round gasket ring from kit and replaced old, different gasket in auto choke. Auto choke working now. Plugs have little to no soot.

One day in here it wouldn't start. No spark. Replaced points and it ran.

Exhaust leak in engine compartment. Ran using Seafoam and good bit of smoke. Purchased open-end, offset crowfoot wrench set for 2/7 and 4/5 manifold nuts. Re-torqued manifolds and exhaust pipe.

Posted video.

Checked 5 exhaust lifter. So much excess clearance that it would perceivably tap when cold and not running when I vigorously moved lifter with my fingers. Adjusted.

Most recent: Ran using Seafoam and still has good bit of smoke in engine compartment.

Next: I will remove valve covers and use smoke machine with exhaust valves open.

Other: Using 20W-50 diesel. Removed spark plug leads which didn't affect sounds except slower.