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Joined: Mar 2015
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Grease Monkey
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Grease Monkey
Joined: Mar 2015
Posts: 15 |
Having issues with backfire when going down hill. Is this a timing issue or carb adjustment? Running regular non ethanol gas.
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Joined: Nov 2002
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ChatMaster - 7,000
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ChatMaster - 7,000
Joined: Nov 2002
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Check for an exhaust leak at the exhaust front pipe to the manifold. It's my understanding that when going downhill and not accelerating the unburnt fuel that passes thru is ignited by the air/oxygen being draw in thru the leak causing the backfire.
Steve D
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Joined: Jan 2002
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ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
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It is most likely to be an ignition problem (interuption) or a leak in he exhaust sysem such as the manifold gasket or manifold to exhaust pipe packing. Leaks in those areas allow oxygen to be inhaled on deacceleration causing gas build-up in the muffler to ignite.
Ignition wise possible condenser.
Last edited by Chev Nut; 04/29/18 12:11 PM.
Gene Schneider
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Joined: Nov 2001
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Tech Advisor ChatMaster - 25,000
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Tech Advisor ChatMaster - 25,000
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The Mangy Old Mutt
"If It's Not Junk.....It's Not Treasure!"
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Joined: Sep 2009
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ChatMaster - 6,000
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Might help for us to give advice if we understand that it is backfiring as you stated or is it after firing. Backfiring means that it is firing back through the carburetor. After firing is out through the tail pipe. Did you mean backfiring or after-firing? Hope you get it fixed soon, Charlie 
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Joined: Jan 2002
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ChatMaster - 25,000
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ChatMaster - 25,000
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That is a new one for me......
Gene Schneider
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Joined: May 2002
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ChatMaster - 6,000
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ChatMaster - 6,000
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After firing isnt a common term but is a good 1 and often occurs as mentioned especially with late timing and exhaust leak close to the engine. Excess fuel still burning or reigniting in the manifold after the exhaust valve opens can cause it too under the heavy deccelaration conditons.
Tony
1938 1/2 ton Hope to drive it before I retire
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Joined: Jan 2006
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Hall Monitor ChatMaster - 7,000
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Hall Monitor ChatMaster - 7,000
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My experience with popping out the exhaust on deceleration is a lean condition. It's quite common on carburated engines when someone puts free flowing exhaust on without rejetting the carb. It can also be caused by air getting into the exhaust stream, mixing with unburnt fuel and being lit off by a hot spot. FYI oxygen does not burn, it supports combustion. I cringe every time I see a movie or TV show that shows oxygen tanks exploding. Obviously the producers/directors slept through science classes in school.
Last edited by Tiny; 04/30/18 08:03 AM.
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1938 HB Business Coupe
1953 210 Sedan
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