won't start when hot

cuzncletus

cuzncletus

Senior Member
My flathead in my 39 won't restart after the car has warmed up. The engine is a 270 inch 8ba, aluminum heads, two 94's, cam, chevy distributor by Bubba with a Pertronix. I thought it was vapor locking so I rerouted the fuel lines. Not the problem; plenty of fuel and good (3 lbs.) pressure. I tried some ether but it wouldn't fire on even that so apparently there is no fire.

I don't want to just start replacing parts but want some advice on where to start. My first thought is the coil might be opening up when hot. It's on a bracket I built off the right thermostat housing. If it's not that I'm going to be pretty well lost as, like a lot of hobbyists, I get quickly confused by little sparky things.
 
If you bought the ignition setup from Bubba im pretty sure he will sort out the problem for you...when issues arrise...call the supplier...if they are standup guys they sort it out.
 
Valves tighten up sometimes and if yours haven't been adjusted in a while, that may be your problem. Take a couple plugs out and get the hot and cold compression reading. Flatties are the easiest in the world to do this on..
Considering that your battery is fully charged and in good condition --
If you have slow cranking speed, you may want to check your ground straps for good connection. Starter motors will try to draw more current when they are hot and a poor ground connection can easily push your current requirements beyond the capability of the battery.
 
Cranking speed has always been good, no drag or hesitation. The starter is an aftermarket 12 volt as is all the wiring. After sitting all night the car fired when I hit the key this a.m.
 
Male sure the spark plugs wires are correct. I had this happen mine was the two on the rear on the passenger side were cross. When hot would not start but cold would. A cheap test
 
Take a wooden or rubber long handle screw driver and ground out each cylinder when the car running. When you do this the engine should die down a little bit. BUT if it don'T AND TWO CYLINDER don't die down Check out if cross.
 
On my 39 ford had same problem. When going to 12 volts remove the resister under dash if still being used. Points are better your flathead will not blow out the spark low rpms, with 12 volt coil and resister. if still don't start get 2 post solenoid for 12 volt. that will by pass the resister just when starting.
 
My '39 would be hard to start when hot. I determined that it was corn gas boiling out of carb and flooding the engine. I blocked the heat riser in the intake manifold. Starts much better now.
 
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