The Stovebolt Site Forums The Shop Area Engine Shop Carb Boiling Over

yes, the carb.

The gas gets hot, and percolates, then boils the bowl over, and gas overflows and runs out of the lower linkage all over the hot manifold.

I got rid of the Rochester B, and replaced it with a rebuilt Carter YF, and added the spacer/insulator, too.

It doesn't do it all the time, but enough times to bug me.

What possible remedies have been tried?


Suggestions please?

Stuck heat riser.....

Is the heat riser that counter weight thingey on the manifold?

Thanks, that might be the problem. I will look in the manual to see if it contains specs to check it out.

It could be excessive fuel pump pressure.

Is your bowl vent working?

obviously to good.

bowl vent? I'm not sure the Carter YF has one. But the leaking comes out below the bowl where some linkage goes up in there, suggesting that the bowl overflows inside the carb I guess.

Every carburetor I have even seen or rebuilt (which has been hundreds) have got an atmospheric vent for the float bowl, if it did not, the gas could not be drawn out through any of the jets by vacuum.
However, external flooding on these carbs is common. Over choking, excessive fuel pressure, defective float/float valve & seat and in some cases to small diameter of fuel line from the pump to the carb can cause this issue. Question first is? Is it really boiling (from temperature) or being forced out by a pressure issue? Fuel pump pressure and volume test at the carb inlet would be a good test to start with.

how would I go about checking fuel pressure at the inlet? do I need gauges?

but it runs fine most of the time,, it just gets upset sometimes, and it is acting like a heating issue.

I will follow through this weekend with checking the operation of the heat riser spring valve, too

scotricker

You say the carb was rebuilt.
I read in another forum that some aftermarket carter rebuilt kits contain replacement parts designed for ford.

heres a copy and paste of the passage
The issue with the aftermarket rebuilding kits is quite simple. The carburetors made for Chevrolet were made in the 1950’s and early 1960’s. Most of the YF production was for Foorrdd engines, especially the 300 CID 6 cylinder which require more fuel. MOST (not all) of the current aftermarket repair kits contain a fuel valve designed for the Foorrdd engine which has an orifice of 0.101 inches. The fuel valve as used in ALL of the YF carbs for Chevrolet had an orifice size of 0.081 inches. If you do the math, the valve for the Foorrdd has an orifice size which is seventy percent larger! Using this valve in the Chevrolet carburetor will cause at best an over rich condition at idle, and at worst flooding and fuel leakage.

Just something else to look at

Good Luck

Possibly a small piece of dirt getting into the needle and seat? Have you cleaned the inside of the gas tank or checked it?