Originally Posted by Eric64
I'm needing some insight, I have a 64 Chevy van that I put a stock 350 with an Edelbrock carb (1406) Granted it's hot here in the desert. I'm sure you all know but the engine is between the seats. I have an aluminum radiator and it seems to be working great 185-200. I did cut the floor out in front of the engine conpartment and fabricated a tunnel/console to allow more air to the radiator. Here's where the question comes in after driving for about 1/2 hr. or so in stop and go traffic you can here the engine start to run rough and start to lose power(dramatic) sounds like almost the gas is vaporizing before it even gets to the float bowls sounds kind of like sizzling/popcorn and basically stalls unless I flip open the engine cover and let the air out. As you drive with it open it eventually starts running better. The air cleaner if mounted on the carb. Would it help to have an intake snorkel going to an air cleaner in a cooler spot, below the engine? in front of the radiator? Can the air going into the engine get too hot for the engine to run properly? When the temperature outside is below 90 it runs fine idles super smooth and accelerates great, over 90 and especially over 100 after thing get hot it barely runs in traffic.
Yes the temperature of the air going into the carb has a big effect on operation. Cooler is better, to a point, sourcing air ahead of the radiator and ducting it to the air cleaner snorkel would be beneficial.
It is possible that you are also getting some vapor lock. This is common in hot weather where between the tank and the engine driven pump the fuel line is a pressure reducing suction. The lower pressure drops toward the fuel's vapor temperature and the heat off the road is soaking the fuel upward toward its vapor point. On a hot day these two events collide in the fuel line to make vapor which the pump can't pump so the feed to the carb becomes intermittent or may fail altogether.
Another thing is to have an insulator between the carb and the intake. The stock intake has an exhaust crossover from left to right which heats a chamber under the plenum floor of the intake. This is intended to force fuel vaporization within the intake when the weather is cold and humid. Not something that happens much in Tucson. There are intake gaskets sold that blank off the cross over port which will cool the intake down toward engine operating temps instead of having this hot spot running at 4 to 500 degrees. Going along with this system is sometimes an exhaust flow valve in the exhaust located on one side between the manifold outlet and the head pipe connection to it. If it's there it should be removed.
Another thing to check if the original snorkel air cleaner is used is the heat pipe from the exhaust manifold to the snorkel. There is a temp and vacuum controlled flapper valve in these that usually quits operating with age in the preheated air from the the collar on the exhaust manifold. If this is the case disable the flapper valve into the closed position. If this feature has been removed there will be an open hole on the underside of the snorkel which will draw hot air, plug that hole.
Stop and go in hot weather can really push the underbody temps up. I have a temp gauge that monitors air temp under my slammed truck, sitting in stop and go traffic on a 90 degree day, which we don't get often, it will read 140 degrees air temp just behind the transmission crossmember where the sensor is mounted.