I have twin Chrysler 440 in my boat with Carter AFBs. I wanted to run my carb problem by an expert before I tear into my problem carb. One of my carbs was rebuilt this past spring. Since that time, whenever I shut down the engines, the rebuilt carb seems to absorb the heat from the engine and gas seeps out the bellhorn gasket and through the manifold/carb gasket, at the rear of the carb. The other engine has no problems. Both carbs run efficient when operating. It's at shutdown when the problems occur.

1) Is there a gasket for the base plate that may deflect the heat better?
2) How do I keep the carb from getting so hot after shut down that it boils the fuel, thus seeking its way out the gaskets?
3) Should the gaskets (bellhorn, base plate) have a sealant?
4) I have also seen gas trying to seep out the fuel inlet fitting.

I think the carb is so hot it's forcing the gas out the weakest points.

Any help would be appreciated!

 

I'm not familiar with marine requirements, but you can buy insulator gaskets. O'Reallys actually stocks some of them here

Other than that, is the fuel supply system, IE pumps common to both carbs? If they are separate, maybe one pump delivers more pressure, or the tube routing may be such to encourage boiling/ vapor lock in the tubing

It may be that the new? needles/ seats aren't very good, or that the floats are set too high.

One thing you might try is to swap carbs between engines.

 

Thanks for the info. I didn't know about an insulator gasket. Do you think that such a gasket would cool down the carb body enough to keep the fuel from seeping out the bellhorn gasket also?

The fuel line from the pump to the inline fuel filter is copper and is close to the block. Any recommendations on such a heat resistant wrap to cover the fuel line?

I've thought about swapping carbs. However, the opposing carb is dialed in with that engine. I've afraid (with my luck) that once I swap it, I will mess up a good thing-on that engine.

Thanks!

 

Insulator gasket is a good idea regardless of it being your problem. Like said Check the float level. I may be set too high. You may need longer carb studs too with an insulator..

 

Insulate your carbs and fuel line from heat as much as possible. Heat is your enemy. Run your fuel line so that it is away from the motor until it has to go to the carb inlets. Use insulating spacers under the carb(s). And insulate your fuel line if possible. Make sure carb fittings are tight. Also tighten all the screws on top of the carb. All of this should help the situation. Good luck!

 

Thanks for all the input. As I have time this week, I am doing all the suggestions and will hopefully run it this weekend with an update to follow.

Thanks!

 

Just one example of an insulator gasket. I found some at the local O'Really parts store. I'm still in shock

http://www.summitracing.com/parts/EDL-9266/

I don't know how old your engines are, so be careful of the bolt pattern. Modern AFBs have a "dual" bolt pattern, the outside ones are the same as this Holley 4bbl pattern. But some early manifolds use the INSIDE, narrower pattern, so you'll need a gasket with the narrow pattern, and some are stamped as the AFB, that is with two sets of bolt holes.