[patrickt]

It's not a float issue. Pull the distributor cap off and inspect the springs and weights, then put a timing light on your marks and watch the movement of the marks as you rev the engine up to 3000 or so. The curve, of course, is based on the spring choice but you should be able to see the marks move smoothly up to a total of 34 to 36. I don't think it's a timing issue though. How do you know your pump shot is working well? Have you put some towels under the squirter, so you're not just dumping fuel down the carb, and then, by hand with the engine off, give several pumps on the throttle linkage and see the gas squirt out with your own two eyes. Do that several times and see if you can get a "dry pump." All pumps should be nice and "streamy" until your float bowl is empty, which is a whole lot of gas. Now, remember, you're working on a cold engine. An imaginative solution would be an accelerator pump diaphragm that only fails to hold pressure when it gets hot. A little GoPro zip-tied to show what your squirts look like while actually driving would disclose that goofy scenario. My money is on a failure to squirt properly.