PCV system in 1941 and 1942 Buicks

[1922bigsix]

Buick introduced a positive crankcase ventilation system (PCV) in 1941 that had a tube running from the top of valve cover to the air intake for the carburetors. This was also used on the 1942 models but by the time they came out Buick recommended that the PCV system be converted back to the pre 1941 system that required removing the tube from the top of the valve cover to the carburetor air intake. The shop manual describes how to do this and states that the new system caused "coking" of the carburetors. What exactly was meant by the term coking?

[Robert Engle]

The steel industry would take Anthracite coal and put it in large  ovens and cook the volatiles out of the coal leaving carbon to be added to iron to produce steel.   The process was called coking.

 

Bob Engle

[2carb40]

In this context "coking" refers to the engine vacuum pulling the oil vapors from the engine into the intake airstream causing "fouling" by having the still "wet" oil vapors deposited on the spark plug bottom and hardening like carbon did when lead was still in fuel. Advice, of course, is worth what U paid for it! So, good idea to verify independently ANYTHING I write about!

[neil morse]

My understanding is that to complete the "conversion" back to the pre-1941 system a draft tube had to be added to the engine to vent the crankcase in the conventional way for the time.  However, based on my experience with my '41 I think the concern over "coking" was exaggerated.  My car has the original PCV system with no draft tube and it runs like a top.  I have also seen photos of a lot of '41's that are running with the original system.

[2carb40]

If your engines rings did not seat properly or are worn, there would be much more chance that oil vapors would make the transition. Im guessing short trips w/frequent stops and starts might also increase problems.

[Matt Harwood]

There were a number of factors in play at the time. Buick also changed to 10mm spark plugs for 1941, so when they fouled the PCV system was blamed and maybe not the rather poor quality of wartime fuels and oils. I think the "carburetor coking" was a theory, not a fact, and many dealers were instructed to drill out the 10mm plugs to a larger, more conventional size suggests they were fighting that problem on several fronts. Who knows what kind of gas they were trying to run through the cars during those years, what kind of extreme carburetor tunes they were trying? I think in today's world of limited use, proper tuning, and cleaner fuels, it's a non-issue. I drive my Limited A LOT and have clean plugs and no carburetor issues with the full PCV system in place and inhaling directly from the valve cover, as designed. And as Greg says, if your internals are healthy, there shouldn't be much oil for it to inhale.

[neil morse]

Yes, the engine on my car was converted to 14mm plugs, as I'm sure yours was also, Matt.

[Eddie-O]

I also have the original PCV tube system in my 41 and have never had any trouble with coking in the carbs since I've owned it. I have driven stop and go and highway driving and she runs like a top.I think if your engine is in good condition with no worn out rings, seals, etc. there would be no need for the change. I think that this is an overblown issue on good running cars. Good Luck

Ed