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#1 |
Registered User
Join Date: Mar 2014
Location: Corona, CA
Posts: 26
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backfiring through carb
im sure this has popped up multiple times, but here it goes again. i have a 72 c20, i replaced the valve covers/gaskets, spark plugs/wires (spark plugs were gaped before installed to .035) after all of this was replaced it started backfiring from the carb, the motor is a 327 off a 67 camaro, my brother and i adjusted the timing and made sure the wires were put on correctly, it idles fine but as soon as i give it a little gas it starts popping from the carb, i sprayed a little carb cleaner in there but im still getting the backfire, i replaced the old vacuum lines, and plugs, my brother said that it might be a loose or messed up valve, im pretty lost now id appreciate any advice or possible solutions
thanks in advance |
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#2 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: backfiring through carb
Could have a bent exh pushrod so the fuel comes in the intake and can't excape out the exhaust valve so fires from compression and exits back out the intake vave which is the carb. Remove covers and run at idle or even unhook coil wire and ground and turn over engine and watch each rocker arm to see if it moves up and down the same as the others, could even be bad cam lobe but prob a pushrod or even broken rocker arm.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#3 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: backfiring through carb
Just double check the wires firing order first.. 18436572. Have even seen a rocker stud partily pull out of the head so look at their length also.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#4 |
Registered User
Join Date: Mar 2014
Location: Corona, CA
Posts: 26
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Re: backfiring through carb
we redid the wires when we replaced them, the previous owner was careless with the truck
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#5 |
Registered User
Join Date: Mar 2014
Location: Corona, CA
Posts: 26
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Re: backfiring through carb
thank you for the help, im definitely going to try that tomorrow, i have the truck idling right now, i am hearing a tick from the passenger side valve cover
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#6 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: backfiring through carb
A tick is usually a loose rocker arm, which could just be not adjusted enough or the rocker stud pulled up a bit so would act as loose. The rocker stud isn't a very common problem, only usually happens when an engine is over reved. But they are only pressed in not screwed so ya just back to pulling covers and having a really good look at each rocker arm and it's lift. The running it part when idling makes it really easy to see quick but can be a bit messy, that is why most would just turn it over and watch. good luck, you will get it. I went back to the double checking plug wires because I have done it myself and would have bet I got them all right, but didn't.
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__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#7 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: backfiring through carb
Just remembered something else, you said it is a 67 engine with plug gap set at .035 so that means you have points, right so could be the condensor, it will make it backfire also. old school stuff. If you do switch up to HEI distrib you can open the plug gaps to .045 and get a bit more performance out of it and also a few more mpg, just a thought on the condensor.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#8 |
Registered User
Join Date: Mar 2014
Location: Corona, CA
Posts: 26
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Re: backfiring through carb
im going to check the valves tomorrow, there might be a loose one, i heard its really messy and tons of fun haha, but first thing ill do is double check the wires, the distributor is pretty big, i know its not stock, ill check what its called
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#9 |
Registered User
Join Date: Mar 2014
Location: Corona, CA
Posts: 26
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Re: backfiring through carb
its a delco remy
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#10 |
Registered User
Join Date: Jul 2009
Location: Porter, Texas
Posts: 115
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Re: backfiring through carb
I would check timing.
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#11 |
Registered User
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 2,149
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Re: backfiring through carb
What kind of carb is it? Is it a Holley?
__________________
'83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project |
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Tags |
1972, 327, c20, carb issues, carburetor |
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