Packard Forum Index » V-8 (1955-56)

Do the 374 engines have replaceable valve seals? she smokes a bit at startup, and im wondering if this is because of oil leaking past old, worn out seals and puddling on top of the pistons.

The other day, it smoked a bit more at startup, then bellowed smoke all the way to the gas station and most of the way back. part of the way back, i accelerated very hard, which cleared up the smoke for awhile. I took it out about an hour later, with huge amounts of smoke. Several hours later, i took it to a car show, and it did not smoke even a tiny bit. I took it out the next day, and no smoke at all. That night i checked the oil, and it was near the add mark. During the runs listed above that she was smoking, it was also blowing the recently shaken loose pieces of a mouse nest out the drivers side exhuast. is this some kind of wierd coincidence? I refilled the oil 3/4 of the way to full this evening but due to rain and no wipers, i will test drive tommorow.

Any ideas engine gurus?????

I'm assuming u have only driven the car less than 200 miles.
The best thing to do is try to get about 500 or more miles on the engine (good long warm runs at 50+ mph) before u attack any of the engine.

Most likely the rings have siezed in the pistons and a good long hot run will help to loosen them over time.

Ive burned off a tank and a half cruising at 45-55 (broken speedo) mostly on the local highway Rte 1. I did "break in" the engine after its long sit with gentel back roads and subdivisions.

They are replaceable. The originals on my car were all cracked, missing or hard as rocks. Machinist did a bit of work to end of guide to fit modern type and replace.

HH56, what do you mean by 'modern' ones? are origanals availible?

There are TWO different valve seals on the V8's from the factory. There is a vulcanized (or similar process) kind of O-ring seal on the valve spring collar. And an umbrella type on the stem.

I'm sure they are but originals were rubber and modern type he used (don't remember what they were for but think GM} were a synthetic material and not prone to the cracking and drying and heat supposedly. One thing to check also is if the baffles are in place. They were added in mid production to keep excess oil from landing on the stems. If missing, could also be contributing (with combination of bad seals) to the problem. See Jan, 56 service counselor.

Thanks! I will see what happens tommorow with the test drive. are either of these seals availible, or is there a cross reference to a new type?

Try this:
Pull one valve cover off. Start the engine and look to see how much oil is getting to the stems. Probably not much or closer to NONE. Then take it for a 5 or 6 mile test run at 60 - 70 mph and report back how much oil ever leaves the trough of the head. I doubt that barely 5 or 6 drops of oil will ever hit the windshield or ANYWHERE outside of the head.

BEFORE u start the engine look at the stems to see how wet or dry they are. Look at them again after a test run.

I think u will find that they are running dry as a bone. Will probably also find about .007-.009 valve stem clearance too when u remove the springs to replace the seals.

I don't know what replacements of original are available. Would NOT use the CUP shaped Umbrel;la types.

On my 56 352 i used a MoPar WIDE SHALLOW umbrella type seal that rides on the valve stem. No seal on the collar only because they were not avilable at that time or i couldn't locate any.

Hi, Mike,

Valve stem seals are unlikely to be your big problem. A valve stem seal oil burning doesn't come and go. Smoke from a missing valve stem seal will be present a bit upon deceleration and a lot upon acceleration after a decel. Closing the throttle at speed creates a very high vacuum. Oil is sucked past the valve guides. Opening the throttle, the cylinders are coated with oil and it burns and smoke is visible. Missing seals will smoke a bit on steady high-vacuum cruise.

1. Is the smoke definitely blue? Black smoke can be a stuck choke, stuck carburetor float, ignition problems.
2. If the smoke is definitely blue, there are only two ways for oil to get into a stock Packard:
a. Valve stem seals, but this symptom doesn't get worse and better randomly.
b. Something mechanical, such as stuck/broken rings, cracked piston.
3. A few Packards from California had PCV valves installed on the. Often this was not done correctly. Often, it was not maintained. Check for any vacuum line going into the intake manifold. This includes a power brake system. Not common on Packards, but one owner of another brand was chasing an oil burning problem while his brake fluid was going out the tailpipe.
4. Head gasket. When a head gasket fails, at high temps antifreeze can be sucked into the chamber and whiter smoke insues. Check the coolant level.

thnx, jack vines