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

Owen,
You can possibly test the valves by shutting off when it's missing, bring the #1 and #2 to TDC and putting air pressure to them, it should hold pressure, and listen for air escaping past the valve.

John

John, thanks for the idea, that's a good thought. I have an air chuck adapter already made up from an old spark plug shell and may do that next, but first I think I'm just going to pull the front valve tappet cover and watch things for a bit.

Compression test and air blowing bach thru the cylinder may not give evidence of sticking valve even if done rather quickly. The 2.0 F engine i mentioned above showed good compression even when warm. Intermittent erradic vacuum on road test only when missing.

The problem is that hte valve sticks ever so slightly open but when given enuf time of a few minutes the spring will draw it closed enuf for good compression reading.

Similar problem on a Tecumseh 3 hp engine. When the engine suddenly stopped and i was close enuf to the engine i could here a 'clink' noise that i did not consider thermal expansion nor contraction noise. It was the exh valve snapping back closed after the engine had stopped for about 10 minutes.

Similar problem on a m/c engine and similar diagnosis.

The F 2.0 engine fought for over 6 months off and on while driving it until i had exhausted all other non-valve related possibilities.

The only way i knew for sure it was a valve was to remove valve cover and spring and to work the valve by hand.

This sticking valve problem is something i have only ran into over the last 6 to 8 years or so. Never had it during the 70's thru 90's.

Some kind of crud is building up on either the stem very near the head of the valve or in the guide very near the head of the valve.

Thanks guys for all the support and ideas. It's beginning to look more and more like a sticky valve, due no doubt to very infrequent use and then only very short trips at low speeds, perhaps coupled with some old gasoline. As of today after a good long drive, the owner reports that the length of the episodes where it runs well are increasing.

Quote:
Dave, Do you have the air chuck made up from a 10MM plug? I was thinking of making one also. Did you weld the chuck onto the plug or would solder work better?

Dave, somewhat fortunately my old Custom 8 has one of those relatively uncommon 356 heads that Packard cast in 1951 with 14mm plugs. I don't think these were made in large numbers. My chuck is brazed to an old sparkplug shell. I wonder if a solder joint would be strong enough - though on household copper plumbing (where the solder film in quite thin!) it easily takes the 100+ psi water pressure.

Maybe consider running some 2 stroke engine oil poured into the gas tank. Many swear by it for the flat head m/c engines. I've never tried it. Probably should tho.

I think the sticking valve idea is most likely. However, another slim possibility is a vacuum leak. I had one in my shop that had a leak in the vacuum antenna. Disconnect it from the wiper motor T and plug it. A long shot I know but . . .
Let us know what you find.

Yes, early on I was suspicious of a vacuum leak and we blocked off the only two vacuum-driven units, the Electromatic and the windshield wipers. The antenna is a rotary roof unit. We even eliminated the vacuum source to the booster pump.

But thanks for thinking about it and posting. If it were my car, I'd be barreling down the New Jersey Turnpike at the speed limit+ right about now.

Dave