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I have a 84 F150 4x4 with a 302 ho out of an 84 mustang. We got the engone from a wrecked truck. I cant get the engine timed right, it constantly misses. It ran fine in the other truck, but when we swapped it to mine, it idled very high. My truck orginally had a 6 in it. We switched the wiring harnesses, thinking that the wiring between the 6 and 8 might bhe different, but that did not help the idling probelm. We rebuilt the carb, which fixed the high idle, but now it always misses. We put a new cap and rotor on it,which did not fix the problem. What could be casuing thius? The truck has open headers right now until we can get it to run smooth enought toget to the muffler shop. Could not enough backpressuer cause this? Thanks
The lack of back pressure is possible. Try getting some cheap header mufflers just to get it to the muffler shop with. It seems funny that it ran fine in the other truck but not in yours. Is there anyway you can use the exhaust form the other truck to test and see if that is it? Just a thought. How about the ignition module? did you pull all the ignition parts from the last truck? the mustatngs use a different ignition box than the truck engines. Hope this helps. I had a 88 HO 302 from a mustang in a 78 shortbed for a while. The one thing I did learn is that Ford went to external balancing about 85 and it shook like mad at idle. I got the right flywheel and harmonic balancer for it and it ran like a champ.
Did it miss before you rebuilt the carb? if not, then I would be tempted to check out the carb and all it's connections before going elsewhere. Often, when you create a new problem while trying to repair another, go back to the last thing you worked on before the problem raised it's head. That't the most logical place for the problem to be. If it did miss before you rebuilt the carb, then this may not apply, but I hoped it would help. Tbob.