On my 261 with cam and 9:1 compression I'm having hot-flooding after shut down problems.
I have a pair of Zenith 228s on a Offy manifold that is heated by tubes from cast Fenton exhaust manifolds. There are 1" heat insulators under the carbs.This has worked well for years but in the past few years I've had hot start problems where the carbs flood the engine. I put in a low-pressure electric fuel pump and everything's fine in moderate temperatures. The repop Carter mechanical had way too much pressure.
So on a recent trip of 4,000 miles, much of it up to 8,000 feet and in hot weather, it floods every time you shut it off. The gas available in high altitude New Mexico, AZ and Utah is 85 octane with 10% ethanol. Back home at 2,400 feet and temps in the 50s there is no problem. But last summer when it was 100 + it would flood but not so bad. I put a pyrometer on it that gave me one more thing to worry about and it says 1200-1300 degrees at 2700RPM under load where it runs most of the time, 2-5" vacuum. Seems hot to me. I'm running 8 deg initial advance and it doesn't ping.When the vacuum comes up and the power valve starts to close, the exh. temp rises. When I'm down to near sea level the temp rises to 1350-1400 at higher vacuum. Foot to the floor it drops down to about 1200 at 0-2" vacuum.
I suppose that manifold heat is contributing but I wonder about the carbs too. Do Zenith 228s have an anti-perculator valve that might be stuck closed? I have had them apart years ago but I don't remember.
