Did he take the spark plug wires off. Check firing order FIRST. Vac line check second (check dizzy advance can for holding vacuum). Check egr vac can for tight. Check float bowl setting - may be low. The sound from the primary is fairly normal sounding from your description. Would you say it's equivalent to a 6psi air leak in frequency. Add the wet gas sucking sound from the idle jet for the liquidity. The spitting could be mis timing firing from cross wired ignition wires or cracks in the dizzy cap, or carbon track arcing paths on the inner surface of the cap, or even induced spark caused by running ign secondary wires to close and too parallel for too long a distance.

To check the jet valves for lost heads, remove the valve cover and set the timing on tdc for #1. On the intakes with closed valves, back off the jet valve lash aduster and see if the stem pops up too far. Turn the crank one compete rev to tdc on #4, and the rest of the intake valves should be closed. Repeat the jet valve inspection.

Check the brake vacuum line for cracking at the manifold nipple on #4. It's in close proximity to the heat from the water passage in the mani from the head, and it can get internal cracking that leads past the clamp to atmo ambient, causing a big vac leak in #4, and lean misfires. Lean misfires are worse on a cold engine, and worse under engine acceleration, especially under load.

The vac lines around the egr on the carb heat rot early. Check close.

Happy wrenching....