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Discussion Starter #1
Hey guys, my 68 gto 400, 4 speed, has began backfiring when I put my foot into it. It is backfiring right underneath me, not at the end of the exhaust. I checked the timing and it is good (14 advance at idle) that is where I have always ran it. It also began surging when coming to a stop. Are these problems related? they both began around the same day. Thanks
 

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Is it only on driver side? You could have a dead cylinder, ignition related. The fuel/air mixture igniting in the header/manifold. Get an infra-red temp gun(very useful), and check the temp at every exhaust port after running the engine for a while. If you have a dead cylinder, it be cooler than the rest. Then check the plug and wire on that cylinder, or cap and rotor.
 

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Discussion Starter #4
backfiring

Carb is two years old. Never had any trouble. Its an edelbrock 750. Is there a safe idle setting I can do? I'm not a carb guy. I think the book says 1 half turns from lightly seated. But I haven't tried it
 

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Sounds too lean to me. I'd check for vacuum leaks/carb mixture. Try this: at idle, take the air cleaner off and mist a small amount of carb cleaner into the carb. If it speeds up and smooths out, it's too lean----caused by a vacuum leak or the carb itself.
 
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