carb backfire
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Junior User
Joined: Feb 2003
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carb backfire
My 79 351m backfires though the carb when its cold. After she warms up real good it runs fine. I have played with the choke and timing but nothing seems to correct the problem. Any one got a thought? THANKS
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Junior User
Joined: Feb 2003
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Ok I just pulled a couple of the plugs and they had fluffy black carbon on them. May be I am running a little rich. I feel stupid but I must ask you for more help. How do I adjust the fuel mix on a Holley 4150? The two screws on the front sides are for only for idle right???
Posting Guru
Joined: Dec 2002
Posts: 2,003
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From: chicago burbs
i thought a carb backfire was an indication of a lean condition? if not a valve problem. it might be just on the verge of needing the next size accelerator pump squirter. if you say you found fluffy black on your plugs, they might be fouled? fouled plugs gave me a problem with carby backfires when i had a 2x4 tunnel ram on. TIP: don't look down the carb and wing the throttle with fouled plugs! if you've been "playing" with the choke, this could be the source of your fluffy black. i would get the choke where you want it and start with some fresh plugs and go from there.
Posting Legend
Joined: Sep 2001
Posts: 30,255
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Carbon sparks from pieces of that fluffy black carbon can ignite the incoming fuel mix. I have no idea why it would only do it cold unless it is doing it warm but the engine runs strong enuf you don't notice it.
Hotshot
Joined: Dec 2003
Posts: 18,423
Likes: 9
From: iowa
carbon fouling is an indication of a rich condition possible causes are incorrect choke setting, plugged air filter or retarded timing. Possible reasons why only cold is maybe your choke pull off is not working or the choke is just slow opening.
As far as adjusting the holley I am definatly not the person you want to ask my opinions of Holleys are not favorable lets just say my idea of adjusting a holley involves the carb a farm pond, and it's ability to float
As far as adjusting the holley I am definatly not the person you want to ask my opinions of Holleys are not favorable lets just say my idea of adjusting a holley involves the carb a farm pond, and it's ability to float
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