Packard Forum Index » V-8 (1955-56)

My '55 Caribbean has been running great up until the last several weeks. When starting the car when it is cold it has a severe erratic miss. It misses when started and runs very rough for 2 to 3 minutes and smooths out and goes away. If restarted while it is still warm, it runs nice. It feels like it might be getting to mush gas, but there is no black smoke coming out of the exhaust pipes.

Not wanting to tear into the carburetors and rebuild them, I checked the ignition areas first by replacing the coil, rotor, and points. The cap looked good and appears to be fairly new. I checked the timing and it was fine.
Any ideas of where the problem could besides rebuilding the carbs?

Sounds like you may just need an automatic choke adjustment. Choke function would also be affected by the manifold heat riser valve so I'd check that as well.

X2 on it being in the choke adjustment. Try less choke and higher fast idle.

That's why 2 x 4-bbls had a short, troublesome life on production cars. They are difficult to keep synchronized, use way too much fuel and only make more power in the higher RPM ranges where few luxury cars went.

jack vines

I had a guy drop by who use to own a carburetor shop to get his opinion. He doesn't think it is the carbs. He suggested that maybe it is a sticky valve. After he left, I noticed a puddle of water (maybe 2 tablespoons) I'm wondering if it could be a blown head gasket.underneath the driver's side tail pipe.

That is just condensation. Find something else to worry about.

Fully agree with Jack--am frankly amazed that so many folks have their shorts in a wad to get two four barrels mounted on their Packard. The most consistent source of headaches in the old car business are carburetors and fuel systems. Its like wishing for an extra mother-in-law.

Well, an extra mother in law is strictly a NO NO!!

With the air cleaner off and while the engine runs rough for the first several minutes, the front carburetor made an unusual air flow noise when it would run poorly.

I performed a cold engine compression check (throttle wide open) and found values ranging from 110 to 123 psi. I drained a quart of oil from the engine and replaced it with a quart of Marvel Mystery Oil. When I started the engine, it ran rough like before and settled down after 3 or so minutes. I let the engine run for about 15 to 20 minutes to get warm.

After allowing the engine to sit for 4 hours to cool, I started it up and it ran fine. I ran it long enough to get good and warm. I repeated the process about 4 hours later that day. The next morning after sitting over night, I restarted the engine and it ran fine with no rough idle. I have since tried it now three different mornings without any idle issues.

I'm guessing that the problem must have been a slightly sticky valve or maybe an issue with a hydraulic lifter.