Had been having hot start issues for a long time with an all stock 59k mile 73 Riv 455 Q-jet. Starts OK after being off long enough to get gas at station but much more than that and it does not want to start. I suspected maybe it was flooding but wasn't sure. Then finally when I was cranking it trying to start there was an explosion in the left muffler. I assume from too much raw fuel getting dumped in somehow. Cold starts are fine and it runs well without any other problems. The choke is verified to be working properly. I am using a 1/4" thick insulating base gasket. No indications of engine overheating which might cause excessive percolation. It has a new brass re-cored radiator. I took the carb apart today to investigate cause but not seeing anything obvious. The float chamber was bone dry. This is after sitting for only 3 weeks. I'd expect there to be some fuel left as I can leave gas in an open container on bench and it doesn't all evaporate in 3 weeks. I put about 1/4" deep fuel in the float chamber to check for leaks in the well plugs but there are none. The float setting was correct and needle appeared to be in good condition. There was evidence the carb had been apart before I got the car assuming for a rebuild kit. Any suggestions are appreciated on where to go from here.
Jason. I would check for leaking after shut down in this manner . After shutting down take air cleaner lid off and see if you see any drips down the carb throat. Sometimes you will see whiffs of smoke vaping off the throat. Also Our older cars do not have a closed fuel system like the newer cars. My carbs on all my older cars definetly are out of fuel from evaporation after a few days. They all require about 4 crank rotations to get gas up to the carb to fire. I know my well plugs are sealed. I consider it modern gas in older vehicles. I failed to mention I don't see 3 weeks as bad. I notice mine could happen in less than half that time.
Between the heat of the engine and the ethanol in the fuel, that will be enough for the fuel to evaporate fairly quickly. How hot does the engine run? The thick gasket helps, but radiant heat off the intake will heat the carburetor.
Since it only has an idiot light not sure on exact operating temp. There are no other indications it's running too hot. Timing has been verified and advanced as much as possible over spec without detonation. Any thoughts on why/how it's flooding so quick? Even if fuel was percolating wouldn't it just evaporate instead of flooding the engine? I did verify no holes in float. Thanks
