just signed up. i've had my 69 f100 390 three speed manual for about 4 months and since then it has gradually developed a few problems. first whenever i sit a light, give it gas it severely loses rpms almost stalls out and then slams forward, almost like too much of either gas or air. i have tried adjusting the carb but i can crank the adjuster screws all the way in and it will not make a difference. im starting to wonder if i possibly need a new carb. secondly the person who owned the truck before me put in an electronic msd ignition and distributor, but the distributor does not have a vacuum advance on it, the carb however does, could this be my problem or cause problems bown the road. finally the guy who owned the truck left a 4bbl holley carb and manifold. if i put that on would it be to tremendous of a project to do? thanks for anyone who can help me its driving me crazy- oops one more thing when it runs for about 10-15 minutes it starts to idle funny until it just flat stalls out and smells of massive gas. thanks

 

Give us a bit more information here. Is the truck still using the original oil bath style air cleaner? Have you cleaned it thoroughly with varsol and then put in fresh oil?(careful not to over-fill it) Secondly, is there a place on the distributor where there should be a vaccuum advance? It would seem strange to me that the vaccuum advance is not there on an upgrades ignition system. Something else to check as well. This truck would have come with points ignition originally. The wire used to feed the distributor power(should be red, running into the side of the distributor) may still be the original points system wire. Points systems used a resistive wire, that upon initial start-up ran heavy load, and then backed off on the voltage. If you can, follow this wire back to where it plugs in inside the cab, and replace it with a non-resistive wire. The ignition system could simply not be getting enough power.
As for the carb, if adjusting the idle/air mixture screws makes no difference, something is definitely wrong there. New carbs are relatively inexpensive for these trucks. I personally don't recommend the holly carb/intake combination, but I've never been a huge fan of them. If you're not planning on changing camshafts, a low to mid-rise intake and small four barrel are best. To many people go gung-ho and slam the biggest intake and carb on an engine that fits, and end up very disappointed with the performance gains. A mid-rise dual plane intake, and 650-700cfm carb are all a daily driven, otherwise stock engine requires. If you keep the size of the carb and intake down, your engine vaccuum will remain up where it's supposed to, and the engine will run normally. To big of an intake and carb and the vaccuum falls and you'll constantly be burping the engine at red lights to keep it running.

 

ok yes the original oil bath air cleaner is on there it has been cleaned out new air filter. the breather caps on the valve covers do seem alitte gummed up. the distributor is a msd billetproof, it has no vacuum advance, however the carb does. i think that may be the problem for the hesitation. also it has been converted to electronic ignition and has no point or condensor. thanks for the tip on the intake/carb i think i may stay with the original style 2100 carb and go from there.

 

Is the vaccuum advance feed on the carb plugged/blocked off? If not, make sure it is. If the distributor has no vaccuum advance, then it shouldn't affect things to much.
I'm aware of the ignition not having points or condensor, but originally it did. If the wire for the points was re-used to feed the new distributor electricity, it will likely be the resistive wire, and will not deliver enough voltage to the distributor after initial start-up or higher revs.

 

oh ok i understand now about the wiring. red wire to the dash. ill check that one in the morning. it makes alot of sense because i was looking at the wires coming off the ignition and the did seem rather old. the vacuum port on the carb is plugged with a rubber hose and a screw. i appreciate your help alot.

 

Not 100% sure here, my 69 did NOT have a resistor wire with the original points ignition. When I went to MSD I kept burning up coils, so I went to a later model ignition and still burned up coils. When I put in a ballast resistor on the wire y'all were talking about I quit burning up coils. My point: Could the coil be bad? It fits with running bad when warm. Maybe a resistor is needed, rather than needing to get rid of one. Like I said, I'm not 100% sure on this. Just sharing what I ran into.

 

ok guys and gals i think ive got this figured out. today i went out to my truck to discover gas laying on the manifold. how i discovered this was yesterday i cleaned what apeared to be oil off the manifold, but it wasn't it was gas sitting on the manifold. it was leaking from the economizer valve and gasket. these puddles have always been there and i thought they were oil. so could this be my problem a leaking economizer valve and gasket? it seems logical to me. lemme know if im wrong or not thanks!!