Expert: Brad Sears - 12/23/2007

Question
Your advice before helped out greatly, so I'm back again :-)
Two guestions actually, what are the general rules of thumb for the mixture screws at the base of the Motorcraft 4200 4bbl carb? After the rebuild, I thought i had them set correctly, but apparently I don't.  I had back them out 1&3/4 turns each, but that seems incorrect.  Also, How do I adjust the points?  After I runs for a while and gets warm, the car is hard starting.  Any advice would be helpful.  Thanks in advance.

Answer
One and one half to one and three quarter turn out is a base adjustment only. Then warm up the engine and with either a tachometer or vacuum gauge hooked up turn one adjustment screw either in or out till you get the highest vacuum or RPM reading. Then repeat with the other screw. Next make sure that the wheels are blocked and the emergency brake is set. Out the car in gear and adjust the throttle stop screw to get the engine to idle at 550 RPM. While the car is still in drive tweak the idle mixture screws one at a time to get the highest RPM and reset the idle speed. If the car is air conditioned turn on the A/C for the final adjustment. This won't help the hard starting, that could be a carburetor flooding out.
To adjust the points, remove the distributor cap. Next turn the engine over until a high point on the distributor cam has fully opened the points. Use a 0.016" feeler gauge between the points and loosen the hold down screws on the point slightly. On one end of the stationary point there should be a slot with a slot opposite it in the breaker plate. Use these slots with a screw driver tip to move the stationary point till the feeler gage just fits in between the points, a snug fit. Tighten the hold down screws and recheck the gap with the feelers. Make sure that there is a little grease on the distributor cam otherwise the point rubbing block will wear down very quickly and change the point setting. Good luck.
Brad