Jump to content

Carburetor Barely Warm but Gas Was Boiling!


Recommended Posts

I have worked in fuel systems for 30 years, but this is the first time I have ever seen anything like this:

This morning (which was cool so the A/C was not in use) we had driven my wife's 1976 Oldsmobile Cutlass Salon with 350 4-bbl about 15 miles at moderate speeds when it began stalling at idle, requiring me to re-start it with the gas pedal to the floor. When we could safely pull off the road, I opened the hood, removed the air cleaner . . . and was greeted by a QuadraJet carburetor that was boiling to beat the band but which was barely warm to the touch!  I had never seen anything like it.  I'd call it "heat soak" --- except that there was very little heat involved!

We use only 93 octane ethanol-free gas in that car (from a local chain here in western NC called Quality Plus Gashouse) and we have never had a problem with it in any vehicle. My only surmise is that either I pushed to wrong button on the gas pump or somebody put gasohol into in the wrong underground tank at the station. Still, even though gasohol boils at a lower temp than "pure" gas, this was ridiculous --- I could very comfortably "hug" the carburetor with both hands for as long as I wished!

We proceeded to the nearest Quality Plus and filled the less-than-1/4-full tank with 15 gallons of 93 octane E-free . . . and before too long all was back to normal. 

 

What the heck is going on?  Has anyone else had an experience such as this?  Or am I the only "lucky" one?

Jeff Dreibus

Nebo, NC

Link to post
Share on other sites

Gas was probably E15 and not marked at the pump. It will boil at 107 degrees if memory serves me. I like my cars 100 percent stock. To be honest, any car post 1972 I would be tempted to run a aftermarket throttle body on, with an electric fuel pump. It will eliminate a bunch of issues.......vapor lock, hot soak, hard starting in the heat, fuel mixture under all conditions will be correct. I hate to surrender to the fuel problem, but basically you car would end up being much more enjoyable and it’s basically a hidden upgrade and easily reversed. Recently I helped a neighbor do a similar conversion down here in souther Florida. It was a very low mileage car, and now it runs and starts like it should........it was a 50/50 proposition to get it running when it was over 90 degrees down here. 

Edited by edinmass (see edit history)
  • Thanks 1
Link to post
Share on other sites

Wouldn't be the first time someone put the wrong gas in a gas station underground tank.

 

Or, the boiling gas may have used up enough internal heat that the outside of the carb felt cooler, but down in the bottom of the fuel bowl and throttle bore it was still hot enough to boil that gas. 

 

I've seen carbs with frost on the outside that melted quickly once the engine was shut off and heat quickly reached the outer parts of the carb. Used to happen with a Cal Custom open element air cleaned I used on a Holley four barrel, on my 72 AMX on some damp cool  mornings going to work. The engine staved for fuel just like it would with vapor lock, but it was carb icing down in the throttle bores. About the time I'd coast off the road, get the hood and then the air cleaner open to check it, it had all melted from the heat coming up from the intake manifold's exhaust crossover hot spot.

 

Took a few tries to catch it soon enough to see the ice down in the throttle bores. Made a twin snorkel air cleaned housing and a couple of  strap-on ducts to pull heated air from around an exhaust header tube on each side to feed heated air to the air cleaner.  Then it never iced up again.

 

Paul 

Link to post
Share on other sites

Edinmass,

 

Thanks.  You may be correct about the 15 percent ethanol, although I suspect that it was a mistake on the part of the gasoline hauler since Quality Plus advertises nothing above 10 percent ethanol content.

 

I would feel like a total hypocrite if I changed the car over to F.I.; I actually restore carburetors for a living and there has to be some way to overcome this problem.  I'm going to install a 1/4" phenolic spacer beneath the Oldsmobile's carb and see if that helps . . . although I doubt that I will notice the difference so long as I don't accidentally get another tankful of ethanol-laced gasoline.

 

What you have noted may explain a trend I have been seeing lately in my work:  I am getting fewer downdraft carburetors as time goes by.  The majority of my workload is now comprised of updraft carburetors from earlier cars.  With a few exceptions, they are mounted low on the side of the engine and are exposed to far less heat unless an exhaust component runs directly beneath them --- plus there is no practical way to replace them with F.I. unless you replace the entire engine itself (sadly all too common today).

 

Jeff Dreibus

Link to post
Share on other sites

PFitz,

 

Thanks.  It may indeed have been hot at the bottom of the bowl but the the primary bores were definitely cool since it was percolating out of the bowl and condensing in the throttle bores.  This was obvious because rivulets of gasoline were dripping out from around the primary shaft.

 

I remember carburetor icing.  It used to happen to me when I was a young man living in northern Virginia; I would have to get out and drive my '65 Plymouth Satellite (273 2-bbl) to work on cold winter mornings and the carburetor would start giving me problems.  When I checked, it would look like a ball of ice!  I never did figure out a solution beyond letting it sit and melt; congrats on solving yours.

 

Jeff Dreibus

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...