1963 Skylark Convertibls overheating issue

My wife has a 1963 Buick Skylark convertible. It has an overheating issue like many 215 aluminum V-8 engines. This is what happens. You can drive it for any distance and it seems to be running fine. When you stop and shut off the engine the intake manifold seems warm, boils the gas out the carburetor and it will not start. It seems almost like vapor lock but this is just my rookie diagnosis. When it's been sitting for awhile it will start but not accelerate well till you get it moving.

What's been done:
new radiator
new fuel pump (it was a rebuilt had unseated internal valves and the gas was draining out of the carb back into the tank. Very hard starting
new water pump
removed intake manifold checked for leaks and blockage, found none. We're about ready to reassemble but I'm pretty sure we have not solved the problem. Any ideas? should we reassemble or dig further? If so where?

Thanks for any input.

Sounds like the next step is to reverse flush the block.

It has been flushed (not reverse though) and flow is very good. I don't know if I should reassemble it or dig further at this point.

In other postings I have read about cracked heads as well as head gaskets. Seems like I would either be loosing coolant or having it appear in the oil if this were the case. Is there any way to check this out with testing or do I just have to disassemble and look.

Make sure that flap in your passanger side exhaust manifold is not stuck partially closed. It will cause the exhaust to push back up through the intake (as designed for a cold engine), making the tempature extremelly hot in the intake. Thats what was causing my 61 to boil the gas out. Hope this helps.

It will cause the exhaust to push back up through the intake (as designed for a cold engine), making the tempature extremelly hot in the intake. Thats what was causing my 61 to boil the gas out. Hope this helps.