Classic/Antique Car Repair: 48 Packard, Packard Vaccum Leak

Question
QUESTION: wont idle when warmed up,good vacuum pressure runs perfect when cold valve job recently no leaks around intake manifold have been told it is a valve guide that is to tight when hot it expands tried a different carb that was perfect on another car didnt make a difference have you ever heard of a valve guide that would do this if so any remedies with out taking the head off ,was told to put in some leaded gas and run it on the highway,have put in some seafoam in the gas some one said this might do it give me your thoughts,Pat

ANSWER: Hello Pat,

Old timers used to use top oil for problems like this back in the day. Try some "Marvel Mystery Oil", available at most auto parts stores.

However, to me , this still sounds like a vacuum leak. Recheck all your settings, including timing. Running smooth when cold or fast idle may not necessarily indicate there is no leak present....simply the vibrations may be canceling themselves out at this speed.

Still not working? Contact your local chapter of "Packards International" car club and ask to speak to tier engine and/or 1948 model year expert. There may be some common "fix" to this problem that is particular to this car.

Best of Luck,

Bob  

---------- FOLLOW-UP ----------

QUESTION: I said it was a 48 its a 53 flathead eight It feels like a vacuum leak to me also,but I have sprayed the manifolds with carb cleaner and didnt get any signs of a leak the vacuum pressure is about 16 lbs repaced all intake manifold gaskets ,and valve job from a Packard expert,could it be an internal vacuum leak under the carb in the manifold itself????? I also have some marvel mystery oil in it, I am an old timer

Answer
Hello Pat,

Again, it sounds like you're following the correct diagnostic procedures. I suppose that an internal crack and leak is possible but there's no way I know of to test for it without the manifold off the engine! I am not an expert Packard mechanic but I have never heard of an internal leak like this on a Packard flathead (I have a 1940 110)

As you know, the differences between a 1948 and a 1953 are relatively minor and mostly internal so I don't think there is anything here either.

I think we're back to my original recommendation of getting a marque expert involved. Additionally, there's an article in the month's Auto Restorer about thoroughly tuning up a 1948 Packard, complete with specifications and procedures. If you have any questions as to whether your base tune is spot on, read the article. Also, the author is open to reader questions so consider contacting him also.

I hate crying "Uncle" to a question but sometimes the intelligent course is to admit your own limitations (which are few from what I read!) and do something we men hate to do---ASK!

Bet of luck to the man who owns one,

Bob