Just got a 41 Merc with a 302 and stock two barrel carb. The previous owner told me the carb is new and it appears to be. My problem is most time the car starts instantly without any throttle input, But sometimes I need to open the carb and add air as if it’s flooded. Also the choke is dialed off and doesn't work. I assume it is flooded, but don’t know why it only happens once in a while, but is happening more often. My first thought would be a sticking float valve. Any ideas what the problem is?
Today's gas has a very low flashpoint and can percolate up through the bowl vent and then down into the intake plenum. This usually happens after the car has been run for a distance and has thoroughly warmed up and is then left to sit for an hour or so. Overnight no problem, starts right up in the morning after the excess fuel has evaporated from the plenum. I have this same problem on my Chevy-powered '55 Buick with a Holley 4-bbl carburetor. The only alternative is to keep as much heat as possible from migrating into the carburetor body. I have purchased a 1/2" thick heat insulator and an aluminum heat shield to try to minimize this problem. I'll let you know how it works out when I've had a chance to install them.
You might try adjusting the float a little lower and there are some thicker gaskets that can be used between the carb and intake that will help keep the carb a little cooler.
Check fuel pressure. Had exact problem with my '41 with 302- 2 brl. Pressure was so high it pushed gas thru the float seat. Dropped pressure with a regulator to about 3lbs and OK
You haven't convinced me yet that it is flooding. With no choke it could very well be needing fuel, and when you open the carb, as you put it, you are actually giving it a shot with the accelerator pump. What part of the country do you live in, is it getting cooler? Don't start changing things until you know what is wrong.
In the past I had trouble with the fuel deflector that came in the rebuild kits that fit under the seat so I never installed them again,this was way before the crappy gas and rebuilt a carb in my friends moms torino that was flooding after shutting off. Removed that deflector and the problem went away.
Thanks for all the input. I've only owned this car for two weeks and it's my first two barrel carb. I haven't looked it over well under the hood yet. I took a long look at the carb today and discovered the choke was dialed in very rich and went to choke 3 out of 4 times if I just tapped the choke plate. I guess it wasn't dialed off as I said in my first post. I dialed the choke way off, started the engine and brought it up to temperature. The engine started 10 times in a row without any throttle input. Also found a vacuum leak and fixed that. I think all is well now. Thanks again for your input. take care, Dave
Possibly tank not venting. When fuel gets warm, pressurizes entire fuel system and pushes its way past needle and seat.
The Jalopy Journal
