[Purdy Swoft]

I'm not sure what you mean by the screw on the side of the distributor. If the distributor is original style, the screw on the passenger side holds and grounds the condenser to the distributor housing and needs to have a clean tight connection. the screw on the drivers side that is in the hole in the lower front of the housing, connects the condenser to the lower distributor plate. You could have a loose or weak condenser. If you removed and replaced the head you will know that the set screw and nut on the center passenger side of the head holds the distributor in place.

Here is how I tune mine . Remove, clean and set the spark plugs at .035 and leave them out for the moment, being carefull not to drop anything in the spark plug holes. file the points and set the gap at .022 . Check the gap on each lobe of the distributor cam and the gap shouldn't vary more than a couple of thousants. There has been a lot of problems with poorly constructed distributor cams and upper distributor shafts. Bill Stipe (stipe Machine) makes the best distributor cam and it gives an additional 10 degrees of dwell for a hotter spark. While your in the distributor check the gap between the rotor tip and the plug wire contacts in the distributor cap. I set mine at .035 for hotter spark and they all need to be the same. I turn the engine over and measure each gap. if the gaps vary it will indicate that the upper distributor shaft is either incorrectly machined or the length of the contacts in the distributor cap are uneven. I have had both problems from many suppliers. The cap contacts can be filed for proper gap BUT be SURE that the problem isn't the distrubtor shaft before you start filing the cap contacts or you run the risk of ruining the cap. Timing, With the spark plugs out, I turn the engine untill the timing pin drops in place. I loosen the screw that holds the points cam to the dist. shaft and turn the cam so that the trailing edge of the rotor tip aligns with the number one spark plug wire contact in the dist cap body, with NO clockwise backlash. There will be backklash but the cam needs to be tightened so that all of the backlash is in the counter clockwise direction or the timing will end up retarded. It may take several tries because when you tighten the cam screw the cam will try to move in the clockwise direction. A cam wrench will make setting the timing much easier. I polish the spark plug wire connectors with a Scotch brite or steel wool for better conduction.

Carburetor. Asuming that the float is properly set and the carb. is not leaking I set the idle air adjust screw at one and one half turns off the seat for a beginning adjustment. Depending on carburetor and the possibility of vacume air leaks,, I run the original style Zenith carb with the Gav turned counterclockwise one quarter turn off the seat. When very cold you may need to open the GAV up to one full turn off the seat untill it warms up. If it will only run with the GAV opened WAY up, this usually indicates a vacume leak where the carb bolts to the intake or a warped carb. housing as in the pot metal Tillotson, Marvel and some others.

Maybe some of this will give some pointers. Many things can cause popping, backfiring. I could be typing all day if I covered all of the possibilities but here is a few more, weak coil, bad ammeter or bad connections,resistance or poor connections in the terminal box, shorts in the armored ignition cable bad ignition switch and bad ethanol adultrated gas. Marvel mystery oil is good for sticking valves. Good luck.