350 Backfiring out of the carb - Hot Rod Forum : Hotrodders Bulletin Board
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Old 01-24-2011, 02:50 PM
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350 Backfiring out of the carb

I have a 70 chevy with a stock 350 i recently put a HEI distributor, new plugs, and plug wires (three months ago) and a Edelbrock 600 carb with electric choke(last week). It has recently started backfiring out of the carb. Any ideas what could be causing this.

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Old 01-24-2011, 03:11 PM
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When exactly does it backfire through the carb ? If it was running good until now. Check and see if the distributer is loose.
Or it could be a cam going bad on you.JMO
And re-check the carb adjustment and check for vacuum leaks around the carb. JMO

Cole

Last edited by eloc431962; 01-24-2011 at 03:17 PM.
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Old 01-24-2011, 03:41 PM
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Check the voltage going to the HEI. It must get 12 volts. It will run on as low as 8, but it`ll kick, buck and backfire.
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Old 01-24-2011, 05:09 PM
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it backfires about 45-55 mph (it dosent have a tach) it ran fine for a while after I put the distributor on but went down hill about a month ago
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Old 01-24-2011, 05:45 PM
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Ayuh,... You just changed the Carb,..??

I'd guess the settings, or jetting is Off, 'n it's a Lean backfire...
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Old 01-24-2011, 05:50 PM
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Any audible symptoms, rocker noise? Hard starting?
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Old 01-24-2011, 06:15 PM
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it may be the carb but i wouldnt think so since it was doing it before i put it on, the carb did help for about a week but its back at it again,and it sounds great at idle
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Old 01-25-2011, 02:31 PM
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re-time the engine.

If it does it after you re-time it, Pull the cam out.
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Old 01-25-2011, 03:23 PM
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Quote:
Originally Posted by 1970 CST/10
it may be the carb but i wouldnt think so since it was doing it before i put it on, the carb did help for about a week but its back at it again,and it sounds great at idle
Ayuh,... Fuel Filter,..??
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Old 01-25-2011, 07:32 PM
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Im voting in as a timing issue perhaps. Have you checked the entire timing curve since the backfire?
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Old 01-26-2011, 08:30 AM
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Make sure the firing order is correct...and the distributer cap is completely on...(has a little tab that fits in a slot)...check for vacuum leaks...I put a rag over the carb and spray ether around the carb and listen for a change in the engine noise...not the safest way...but im a redneck and it works..lol..make sure a rocker arm didnt pop off...check the timing...if all else fails its a cam lobe failure.
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Old 01-26-2011, 07:57 PM
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My 383 started doing that on a TBI setup and what happened was the poly lock backed off on #7 exhaust and there was no where for the exhaust to go and that was the culprit. Not sure that is your issue but something to keep in mind.
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Old 01-26-2011, 09:02 PM
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Check to see if all the parts in the dizzy are moving as they should.
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