gml

My ’63 340hp is very long cranking to start. I assume to get fuel back into the bowls but starts up quickly when the bowls fill. Starting usually takes 5 or more cranks, each a 5 second duration. Even restarting later in the day is a lesser version of the same so fuel is leaving the bowls quickly. Looking into the carb I see that the pump discharge nozzle is moist in the primary throat and so is the manifold floor under the carb.

Ideas leading to further testing and a cure are appreciated. I could assume this will require a second professional carb rebuild. But your input about the issues with this type carb is appreciated.

Carb was restored 10 years ago, has seen very little mileage since. I have committed to driving it more often now so I am paying attention to these issues. I really dislike the long oil pressure build up time during this cranking period. Car has seen only Amoco Ultimate Crystal Clear non-oxygenated gasoline since restored. I always cool down with the hood open. I have no reason to suspect other issues with the carb, car runs fine in the neighborhood and on the open road, accelerates with no stumble.

Allcoupedup

I've had two different carter AFBs on my 65 and both did this. One dribbled out and flooded the engine. The gasoline in the other evaporated and took forever to fill the bowls.

You can easliy determine if the gasoline is evaporating by removing the air cleaner and pumping the accelerator - if fuel shoots out of the accelerator pump nozzles - you do not have an evaporation problem. If so, then you have another issue.

Don't know how to fix the evaporation problem - I was able to fix my dribbling AFB with a $10 kit from ZIP.

Brian

chris ritchie

Mine does this too. Don't know how to fix it. Suspect it isn't fixable. There's been a bunch of posts on this subject. Nobody had a solution.

What I don't understand is that this seems to be the first time this condition has come up. When these cars were new, I don't remember these complaints. The answer wasn't that when these cars were new, they were driven every day. Most Corvettes were second and third cars then. Maybe the gas was different then. Can you imagine buying a new car and it's hard to start after sitting a while? Dealer would have heard about that.

clem zahrobsky

if you have a aluminum intake block the heat riser crossover,make sure the heat riser valve is wired open and the reason these carbs did not do this back in the good old days was because of the type of gasoline now sold. if you have a cast iron intake and it has the heat groove under the carb use expansion plugs to plug the holes in the manifold groove

Subfixer

WHen I first bought my 64, it had the 300hp engine in it with a cast iron manifold and the Carter Afb. I never had any starting problem, either cold or hot or after sitting all winter.

In the old days, the trick for a good running AFB was stricked attention to float level settings.

On the other hand, now that I have a 365 with aluminum intake and Holley, it's a whole different story.

gml

I appreciate the responses. After car sits I get no squirt from the accel pump nozzles, thus I assume the evaporation mechanism and will minimize heat to the carb by the suggestions cited.

Though the manifold floor under the carb is moist I really have not sensed flooding during the cranking. With the fuel inlet at the top of the bowl on this AFB there can be no bleed back to the fuel pump, in my opinion. So evaporation it is, manage the issue, not eliminate it.

Has anyone installed an electric fuel pump for the purpose of precharging the bowls? That would minimize the low pressure cranking time. I assume there are types which are placed in series with the mechanical pump.

Thanks to all.

magicv8

I blocked the heat riser ports in my iron manifold and gutted the heat riser valve to no avail - engine heat boils out the gas, which I believe has been reformulated over the years to aid emission control and to give old cars this problem

I cured the problem years ago by installing a low pressure Purolator pump on the rear crossmember (at the gas tank). It also prevents vapor lock, and gives me a safe place to put an in line fuel filter.

Here's apic of it mounted on a trans/motor mount to suppress noise: