Any thoughts on getting this truck running smooth?

Asked by AJKamal May 01, 2020 at 07:06 AM about the 1984 Ford F-150

Question type: Maintenance & Repair

We swapped the original I-6 for a 302 that came
from an 85 mustang. Rebuilt the motor with brand
new everything. Upgraded: aluminum intake, long
tube hedders, HEI distributor, and a 4 bar carb
Holley. We had to change the shift linkage and
throttle cable around to fit because for some reason
they don’t recommend Holley for this truck
although it has nothing to do with mixing fuel and
air. Power has tripled from stock and when I get on
it the acceleration is fine and smooth. But when I
just add a little gas, like keeping cruise speed on
highway, it sputters as if it’s misfiring or getting
flooded or not enough fuel. We checked all the
floats in the carb. Has new spark plugs and 8mm
wires. Any suggestions?

40,015

beatupchevy answered 4 years ago

The carb may be mis matched for the engine displacement , like too big . When you hit the peddle there's an accelerator pump in the carb that spits out a little extra fuel so you may well be flooding it out a bit . not sure if there's an adjustment for that , I know you can replace the metering jets for a lean or richer mixture , There's a certain air/fuel ratio for good performance , 17.5 : 1 or something , what do the plugs look like ? They can be an indication of a rich mix , black and sooty I think .

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F_O_R answered 4 years ago

The carb should be 500 cfm or even smaller for a 302. It is a myth that a 850 double pumper will give you more power. Nascar uses 390 cfm carbs to get 750 hp.

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