[BILT4ME]

If it feels like it's popping back through the carburetor and will not start, it is very likely you have the distributor 180 degrees out. The engine has to turn over 2X for every ONE turn of the distributor.

Take the engine to the COMPRESSION stroke on cylinder #1, then pull the cap off the distributor and note the location of the rotor. It SHOULD be point directly at the #1 terminal on the distributor cap. (I make a mark on the distributor BODY to identify where the #1 plug wire lands on the body, since the cap is off when I am inserting the distributor.

Also, double check the wire connections from the cap to the plugs. Make sure they are in the correct order and start in the correct place on the cap.

We just got done doing this ourselves. I've done it many times, but I was teaching my son how to do it and what to check for symptoms-wise when that happens. Sure enough he had it 180 out.

He found TDC on #1 on the compression stroke by:
Remove spark plug #1
Insert a wet paper towel into the spark plug port
Disconnect the BATT wire from the distributor (if HEI) or remove the coil wire so you don't run spark.
crank over the engine with the starter JUST enough to have it blow out the paper towel. Since the engine will spin PAST TDC, you then know you must then rotate by hand for TWO FULL turns to bring it back to TDC on the compression stroke.
Pull the distributor cap and see where the rotor is pointing. If it's pointing at #6, then it is 180 out.

He pulled the distributor, rotated 180 and reinserted. He was SHOCKED when it immediately fired up!

Good Luck!