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251 L head runs bad HELP!!!!!


johnD400

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so I have installed new plugs ,wires , points ,condenser , coil ,fuel pump , rebuilt carb , replaced cracked exhaust manifold . shes firing on all cylinders . Has right at 118 pounds pressure on all cylinders . I have moved timing all ways possible  .set at factory spec now .   she starts right up and idles fine.   But at im guessing 1000 rpm plus misses bad .if you continue to give her fuel she will start to backfire and stumble bad. I thought she might be starving for fuel so I tried dumping some in to see if she would clear out, but that didn't help. no intake leaks either .    Im out of ideas . I bought the truck long distance and the guy said it ran great . ive dumped another 800. 00 or so plus my time and still runs bad .  If broken valve spring or something would compression still be good ?   Any ideas will be appreciated 

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you need steel core wires. try a new condenser. china stuff can be bad even new. 118 lbs of compression is like a new engine. check the dist. lead wire to the points. the insulation can wear off from the dist. plate moving when you accelerate.    capt den

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1 hour ago, Plymouthy Adams said:

check your points for 17 to 20 ounces of spring pressure on the swinging contact...….could be you are floating/bouncing....

To PA's point is the breaker spring installed correctly?

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Check the Breaker Plate assembly. Take the distributor cap off and remove the rotor, then grab the dizzy plate assembly and see if it moves sided to side and if loose. A friend of mine had a 39 Desoto and the assembly plate had a lot of slop and the car would backfire and was loosingpower. An old time mechanic friend of mine looked at the plate and told us to replace and this solved his problem.

 

Rich HArtung

desoto1939@aol.com

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