[Rick Parker]

Clois: Try this in a safe environment:

Immediatly when this happens shift into neutral, pull the center coil wire from the dist cap and attach a spark plug to it, grounding the body of the plug away from the carburetor. With a jumper wire (6"X 18 gage) disconnect the distributor lead to the msd box. Turn the key to the run position and then repeatedly make and break connection with the two "prongs" in the connector plug to the MSD box. "IF" the previously mentioned spark plug fires each time you break the contact then the MSD box is working. You may be expieriencing fuel percolation that takes place during heat soak shortly after shutting the engine off. This causes fuel to boil out of the float bowl vents and then raw fuel dumps into the manifold.
Be careful to not put the plug near any fuel vapors.
It is also possible that the needle & seat is allowing residual fuel pressure to over fill the float bowls during shutdown during hot conditions, causing problems as stated above. If you don't have spark, then check the box.

Good luck
Rick