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My new 1940 acquisition: Flat 8 Number 2 cylinder is seeing spark but has wet plug. Valve or piston assy seal obviously. All other cylinder combustion looks good. What to do next? Valve adjust or pull head? Burnt valve potential? lap valve required? no gas in oil accumulation. no blue smoke. Car has 50K mile and most likely engine not rebuilt.
How do I go about this efficiently and effectively?

Low compression or no compression in #2? Remove the valve covers, run or turn over the engine on the starter and make sure that all the valves are moving up and down - it's possible one valve has frozen in an open position though if so you'd probably be hearing some ojection from the lifter. Also check for a broken spring. Next thing to do is to check the valve tappet adjustment and make sure both lifters have some (any) clearance; if either one has no clearance, adjust the tappet clearance (might as well do them all) and retest the compression. If you still have none or low, then you'll have to pull the cylinder head to find the cause. It wouldn't be at all uncommon for an engine of that era to require a valve job at 50,000 miles though typically when that's needed all cylinders will have some compression, not one with zero (you didn't give us any actual compression values - if you don't have them, then do a compression test). Whether a simple lapping of the seats, or machine refacing of the valves and seats and possible replacement of one or more valves and perhaps guides depends entirely on what you find when you diassemble.

Here's a primer on valve work that might be good reading for you:http://www.packardclub.org/forum/viewtopic.php?f=14&t=862

Thanks for the advice. Could I possibly have a little rust in the exhaust valve guide causing sticky valve? (repaeated caution in the service manual) the problem increased when I took it out of storage and yes the car went through a number of short start stops in the cold when it was first delivered to me. How would I free this up? Low compression. not zero. I gotta find a better gage. You can hear a small exhaust periodic pop just less of a non- perfect idle. Will continue to post as I go through this.

Could I possibly have a little rust in the exhaust valve guide causing sticky valve?

Absolutely, especially if the car has come out of a long hibernation. This is especially the case with exhaust valves as they run dry in the guide, whereas generally the intake valve will have had a slight film of oil on the stem and in the guide. But if the valve is stuck wide open, you'd most probably have zero compression or near to it and if it was stuck partway open the lifter would be pushing the bottom of the stem every cam revolution. It's possible the valve is lifting and closing but some rust is preventing it from closing the last couple of thousands of an inch and in that case they often free up with continued running of the motor. Worst case to free is up is to remove the cylinder head and valve, clean the stem and guide and reassemble. Yet most folks who have experienced a stuck valve seem to be successful getting them freed up with just patience, liberal amounts of Seafoam or PB blaster from above and below and applying whatever force you exert on the stem and perhaps thru the spark plug hole.

Other good possibilities for low compression could be a bent valve (often resulting from milling the head excessively) or a burned valve which would always be an exhaust valve. Of course there are other possibilities due to the piston and rings, for example a broken compression ring. Noticeable blue smoke from the tail pipe?

G'day 40120sdncnv,
A to PackardInfo, and I invite you to include your '41 120 in the Packard Owner's Registry.

ok. #1 cyl 92 psi. #2 88 psi #3 93 psi. Then the inlaws pulled in the driveway and that is far as I got. lifters toward front of engine are complaining so I think I have sticky valve(s). All plugs look great except for #2 - all wet and carboned up.
Will be traveling so I think I will soak with PB blaster or Marvel Mystery while I'm gone. Then I will decide how to get under her and reach up and adjust the valves (while running or cold? possible? What is recommended). Drove it quite a bit today. Seems like lifters are worse maybe because of carboning in valve - not sure. Also I have a rapid tic toc by the fan in the front like the water pump or timing chain circuit. This car is just starting to loosen up and showing her personality. oil circuits need some help maybe. Any further advice is welcomed.
Maybe I should do a full valve job and get it done right? 90 psi is borderline no? Drives nice - has power - no blue smoke. Heck - its an old wonderful car.

ok. done. a partial story anyway. Thank you all for Packard help.

done. registered. The valve story will continue until solved.

oh - one more question. My car has the original in series oil filter to lifter circuit. Is it advisable to put the oil filter parallel kit on?. Do I really want to drill and tap a hole in the block? Existing circuit contribution to noisy lifters? Oil pressure shows good. oil pressure picked up after lifter circuit or?

for including your '40 One-Twenty Convertible Sedan in the Registry. And good luck with your engine issues.