Will an improper valve adjustment cause a backfire?
Thread Starter
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Joined: Sep 2009
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Will an improper valve adjustment cause a backfire?
The problem im having here is im getting a backfire through the front drivers side barrel of my carb. It doesnt happen at an idle but just when i give it a little gas then poof and the engine dies. I was running a 600 cfm edelbrock then i tried a 750 and that had the same problem and it was too big of a carb anyways. So today i put the 600 back on. So could maybe a valve adjustment be off and thats what is causing the backfire?
Its a newly rebuilt engine so i know its not a rubbed off lobe or a fowled up valve. everything is new with less than 30 miles on it.
Thanks in advance!
Its a newly rebuilt engine so i know its not a rubbed off lobe or a fowled up valve. everything is new with less than 30 miles on it.
Thanks in advance!
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
New motor is more likely to wipe a lobe than an old, well broken-in motor.
Popping back thru carb on a new motor is likely caused by lifters/valves adjusted too tight.
Popping back thru carb on a new motor is likely caused by lifters/valves adjusted too tight.
Drifting
Joined: May 2006
Posts: 1,480
Likes: 2
From: Circleville Ohio
Vader Vette
The problem im having here is im getting a backfire through the front drivers side barrel of my carb. It doesnt happen at an idle but just when i give it a little gas then poof and the engine dies. I was running a 600 cfm edelbrock then i tried a 750 and that had the same problem and it was too big of a carb anyways. So today i put the 600 back on. So could maybe a valve adjustment be off and thats what is causing the backfire?
Its a newly rebuilt engine so i know its not a rubbed off lobe or a fowled up valve. everything is new with less than 30 miles on it.
Thanks in advance!
Its a newly rebuilt engine so i know its not a rubbed off lobe or a fowled up valve. everything is new with less than 30 miles on it.
Thanks in advance!
Thread Starter
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Joined: Sep 2009
Posts: 58
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I adjusted the intake valves when the exhaust was just starting to close and I adjusted the exhaust when the intake was opening. I brought it to zero lash and tightened it a little more than 1/4 turn of preload.
I checked it again, all the wires are hooked up right.
I have it set at 8 deg BTC @ 800 rpm. total timing somewhere around 32 deg.
I checked it again, all the wires are hooked up right.
I have it set at 8 deg BTC @ 800 rpm. total timing somewhere around 32 deg.
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Melting Slicks
Joined: Oct 2003
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St. Jude Donor '08
My new engine had the similar symptoms with under twenty miles. It had the exhaust lobes for 7 & 8 rounded off. Hopefully that isn't your issue, but it might not be a bad idea to check the oil for metal.
Thread Starter
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I went ahead and readjusted the valves. Took em to zero lash and gave em all 1/4 turn of preload. I just discovered I'm getting misfires on some cylinders. I'm also getting a little knock. I now am leaning toward a leaky intake manifold. Ill test the manifold vacuum and get back to you.
Team Owner
Joined: Jun 2000
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From: Southbound
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