Vapor lock or flooding? Mine floods when it sits for about 10 min when shut off hot. I crank with WOT and it starts, letting in lots of air. I blocked off my exhaust ports with a special gasket I got from Butler. There are two kinds. One has a stainless piece that you cover the port as you assemble. What I used was a gasked without the hole, from Butler. I would't recommend it, though. The car never ran right that way, especially on cooler days. I eventually unblocked mine and am happier.