1936 C9 Airflow Intake Valve Sticking

[1937 Buick 66C]

Good Day all,

 

When I went to start my 1936 C9 Airflow earlier this week (it had been sitting for a couple of months), it is exhibiting symptoms of a sticking intake valve.  When cold it cranks unevenly, as if there is little or no compression in one or more cylinders.  Once started, it backfires through the intake manifold and has an audible valve clatter.  After running for a few minutes, the clatter abruptly stops and the engine smooths out and runs very well.  For several years prior to my acquisition this car was used very rarely, and was probably never driven for any length of time 

 

I am guessing that one or more of the intake valves is sticking when cold.  I would appreciate the collective wisdom of the forum on these symptoms:

• Is this a common problem with these engines.  Is there a "quick fix" that is likely to dissolve whatever debris might be hanging up the valve?
• I do intend to drive this car on a fairly regular basis.  How concerned should I be about it since it does free up and works well as soon as then engine begins to heat.

[hchris]

Your diagnosis is sound, most side valve engines that have extended periods of sitting are prone to sticking valves, dont like the mention of clattering though.

 

Have you considered removing the side plate covers to acces the valves and having a look?  If you have someone motor it over you will probably see a valve thats hanging up.

 

As to the fix, you could try a good soak with Marvel oil or similar, worst case would be off with the head and remove the valve, possibly decoke the guide, if its bent then you have awhole more heap of work.

 

Probably a good place to start would be wet and dry compression checks.

[1937 Buick 66C]

hchris:  Thanks for the quick reply.  The clattering quits as soon as the valve frees up and begins working properly, then the engine sounds and runs great. 

 

Where do you suggest application of Marvel Mystery Oil;  Is running some into the intake manifold what you are suggesting, or squirting it on the valve with the side cover removed?

 

Another related question:  This car has not been run much in the better part of a decade.  I intended to drive it much more regularly now that it is in my possession.  Is this type of problem less likely to happen with regular use?

[c49er]

Change the oil ... add some MMO and start driving it regularly ... the valves should not stick anymore.

[hchris]

12 minutes ago, c49er said:

Change the oil ... add some MMO and start driving it regularly ... the valves should not stick anymore.

 

What he said.

 

Alternatively you could start by dribbling some into the intake at idle, expect lots of exhaust smoke initially. Being over cautious I would take the side plates off anyway just to see if there is anything untoward, your choice. 

[Grimy]

Agreed.  For the next year at least, add 4 oz MMO per 10 gallons of fuel just before you put the nozzle in the tank; that will mix it up.  After a year-long dose at every fillup, you can go to every second fillup.

 

I use MMO in all my L-head and T-head engines.  Every spring, I'd have one valve hanging in my (then) two Pierce Series 80s (L-head sixes), and once I began adding MMO regularly, I never had that problem again.