How did you clean the carb? If you just sprayed carb cleaner into it that's not enough. It needs to be disassembled so the jets can be cleaned. There are small passages in the idle circuit that can only be cleaned by disassembly when the engine won't run.

Verify you have a good hot blue spark at the sparkplugs if the spark plugs are wet - there is an ignition problem (bad, coil, wires, distributor cap or rotor) start testing, and looking at parts for cracks, streaking and build up on the distributor cap contacts. A multi-meter is your friend.

couple things, compression is first. second make sure the distributor hasnt broken the drive gear pin. 3rd how are the connections at the dist connector and at your eec module? hows the top of the carb? they loosen off even with loctite and spring modification. also there is sometimes an ignition switch issue(not tumbler) very simple engine, usually problems go back to previous owner mods

How did you check the spark, off of the coil lead? If so, the cap or rotor could be bad.

Just bought a 1981 f150 with a 300 straight 6, 4 speed manul. Guy said it sat for 3 months and needed the carb cleaned. Gas was drained before it sat. Cleaned carb(wasn t dirty at all). Put gas in it, it has spark. Gets gas to the plugs, but it will only sputter for a second every once And a whil. I messed with the distributer a little but that didn t help. What should I try????