GMC Repair: 86 gmc dies when warm, vacuum leaks, pickup coil

Question
Hi, I have an 86 gmc half ton 4x4 pickup. it originally came with a 305 but now has a 1975 350 engine in it. anyway, the thing seems to start fine and runs good until the engine starts to warm. after that it wants to die. i have a manual choke. it seems that it runs the best with the choke off as it should toolin down the road but when i get ready to stop it dies. i tried leaving the choke on some which helps some but the mixture is obviosly to rich then. i do this to try to prevent it form quiting. i replaced the carb with a new 600 cfm edelbrock, put in new fuel line, new filter, and two new gas tanks.also new plugs, wires and coil. i dont know what else to do. it has almost no emissions stuff anymore either. i also cant find any vac leaks, so far anyways. i just dont have a clue what can possibly be going wrong anymore.

Answer
1. WHEN did you replace the 305 with the 350 ?.

2. What did you CHANGE as far as the electronics ?.

3. If memory serves, I believe BOTH engines had an ELECTRONIC SPARK CONTROL MODULE mounted on the firewall, Did you use the distributor from th 305 in th3 350 or did you use the 350 distributor?. I'm thinking about COMPATABILITY between the 2 possible DIFFERENT, ELECTRONIC SPARK CONTROL MODULES.


4. Have you tried REDUCING the size of the jets in the cfm 600 ?.


QUESTION: are the spark plugs fouled with gas or black carbon deposits ?.

You are not supplying to HIGH of a voltage to the + side of the coil, Are you ?. Did you CHECK it ?.


Vacuum leaks are a major problem as well.



IF you have checked and verified EVERYTHING above, The other common fault is an intermittent fault in the PICKUP COIL within the distributor.



Other than the above, You will need to contact me at:


meperganfortis@msn.com


In order for me to send you some electrical schematics, test procedures and pictures related to the PICKUP COIL, As this website is NOT mine and I am only a VOLUNTEER helping answer simple questions to those in need and the owners do NOT allow picturse to be sent..

Please RESTATE all your vehicles information and problem in your contacting me.



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