Gas boiling in carb

[Mark_B]

Hi All,

Hope you can help please.  When I park up my E Body around 2 mins later I can hear boiling in the carb and a strong gas smell.  This started happening around 6 weeks ago.  Do you know what is causing this please and how to fix?  Someone mentioned a phenolic spacer may help.

I did top up my green coolant with some red coolant around the same time, I understand this is not ideal and am changing the coolant today.  Do you think this is related?

Thanks for any help you can give.

[torredcuda]

What carb?

[Mark_B]

It's an Edelbrock 1406 Performer

[chargerdon]

Intake manifold?  and Engine? 

I will say this...not all that uncommon... 

Todays gas with Ethanol in it boils at a lower temp than the old leaded gas.   Often in hot weather the gas will boil out some, so that you then have to "crank" for several seconds to refill the bowls AND often that boiling will overflow the carb and go into the intake and flood the engine.   Again making you crank it for several seconds before it will start again. 

Yes a phenolic spacer if you have room will help.   Maybe put in a lower temperature thermostat...   

[Mark_B]

The engine is a 340 and the manifold is standard.  Thanks for your suggestion.

[bennydodge]

Hi All,

Hope you can help please.  When I park up my E Body around 2 mins later I can hear boiling in the carb and a strong gas smell.  This started happening around 6 weeks ago.  Do you know what is causing this please and how to fix?  Someone mentioned a phenolic spacer may help.

I did top up my green coolant with some red coolant around the same time, I understand this is not ideal and am changing the coolant today.  Do you think this is related?

Thanks for any help you can give.

Pretty typical with all-aluminum carbs. I can tell you from experience the insulator base gaskets sold by Edelbrock are helpful in solving the problem.

[Shane Kelley]

Very common problem and very difficult to avoid with a carburetor. Blocking the heat crossover with help sometimes but not eliminate the issue. I've tried everything. My engine temp runs nice and cool in the 170-180 range. Aluminum heads and intake. Problem is high under hood temps and generally heat soak on everything. Mine is not horrible like some big blocks I have dealt with but slow stop and go traffic it tries to act up. A return line to the tank is very helpful in keeping fresh cool fuel flowing through the lines. But once you park the car it's going to boil out of the carb. Electric fuel pump would help with circulating the fuel and filling the carb back up before starting. I don't like electric fuel pumps so I live with the issue. EFI is the only sure way to resolve it.

[bennydodge]

Yep, I know what you mean, anything high-compression with lots of aluminum makes a LOT of underhood heat. Running the phenolic float bowl Street Demon carb has helped noticeably.

[Mark_B]

Thanks for your help.  I'll look at getting one one those Edelbrock insulator pads.

[Chryco Psycho]

I agree with Shane , pull the intake cut a piece of the old gasket & block the heat crossover , for summer driven cars the last thing you need is exhaust heat crossing through the intake under the carb 

[Topcat]

Here's what I do when I return:

I pull the car in. Right away, open hood.
Point big high volume fan pointing down at engine on top of work bench.

Crack a Beer. 

If it's really Hot, then crack another Beer. 

Start ups on next times are vastly improved.

[Racer57]

I had issues with my 383.  Finally realized that the stainless fuel line was clipped to the frame rail near the exhaust manifold and pipes. The frame was too hot to touch, so I knew that fuel had to be really hot. I pulled line out away from frame and purchased some velco fastened fuel line insulation. Wrapped it in area around manifold and used some on line where its real close to engine. Problem solved. 

[Mark_B]

I had issues with my 383.  Finally realized that the stainless fuel line was clipped to the frame rail near the exhaust manifold and pipes. The frame was too hot to touch, so I knew that fuel had to be really hot. I pulled line out away from frame and purchased some velco fastened fuel line insulation. Wrapped it in area around manifold and used some on line where its real close to engine. Problem solved.

Thanks for this. Yes the fuel line to the carb is resting on the metal rocker breather, so this can't be helping too.

[Shane Kelley]

I've done just about everything one could think of except return line or EFI. Insulated fuel lines, Thermal barrier inside the headers and engine has no heat crossover. But on hot days it still occasionally acts up in slow traffic or after it's parked for a short period after driving it. 

[Mark_B]

I'll buy and phenolic spacer and see if it does the trick. 

Anyone know if a 1" phenolic spacer fit under the hood with the standard air cleaner and R/T hood.