Need help with popping...
Thread Starter
Instructor
Joined: Mar 2006
Posts: 181
Likes: 0
From: Ft Hood TEXAS
Need help with popping...
My 76 L48 has developed a weird popping noise from the right side of the exhaust. At first, I thought that it may be the "custom" side exhaust. However, I think that there may be more to it. At idle, every 4 or 5 seconds there is a "pop". I thought that it was just a noise but you can actually feel an increase in the amount of exhaust coming out of the pipes when it pops. And, like I said, it is only comeing from the right side and to be quite honest, it is reall annoying. Thanks for any help. Here is a pic of the exhaust. Try not to laugh too hard. I am running long tube headers too if that helps.....
Racer
Joined: Jan 2003
Posts: 383
Likes: 0
From: Columbia SC
A friend of mine has a 78 and he had popping while driving when he was off the gas pedal. Not sure if this is the same situation as yours but for him he needed to have his Q-jet adjusted. Seems the popping was actually back firing in the stock exhaust manifold. Right after he got the carb adjusted the popping stopped...
Racer
Joined: Jan 2003
Posts: 383
Likes: 0
From: Columbia SC
you say "lift off the gas" I say " off the gas while driving"...same thing.
I bet your carb needs adjustment. My bet is the carb is running rich and the extra gas is going into the exhaust and then igniting (pop)..
Just a guess
I bet your carb needs adjustment. My bet is the carb is running rich and the extra gas is going into the exhaust and then igniting (pop)..
Just a guess
Racer
Joined: Jan 2003
Posts: 383
Likes: 0
From: Columbia SC
Do a search hotwater, all kinds of posts on this subject...
http://forums.corvetteforum.com/show...light=backfire
http://forums.corvetteforum.com/show...light=backfire
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
The noise is at idle and there can lot's of reasons. I might miss some.
Check for exhaust leaks on the side where the noise is. Air entering the system will cause a pop. Check the gaskets and pipe connections.
Check for a misfire. Check the 4 plug wires for burns or insulation problems. Check the 4 spark plugs for obvious problems. If either are old, they might need replacing. Using a tool, pull each wire off at idle, does the rpm change?
Connect a vacuum gauge and see if the reading is steady. You might need a carb adjustment. Your carb originally had caps on the mixture screws to prevent tampering with them. The factory setting may not be optimal. Does the choke pull off completely at normal engine operating temp?
Check the ignition timing.
You have a very low restriction exhaust from the picture, it will be normal to have some popping but usually out of both sides.
Check for exhaust leaks on the side where the noise is. Air entering the system will cause a pop. Check the gaskets and pipe connections.
Check for a misfire. Check the 4 plug wires for burns or insulation problems. Check the 4 spark plugs for obvious problems. If either are old, they might need replacing. Using a tool, pull each wire off at idle, does the rpm change?
Connect a vacuum gauge and see if the reading is steady. You might need a carb adjustment. Your carb originally had caps on the mixture screws to prevent tampering with them. The factory setting may not be optimal. Does the choke pull off completely at normal engine operating temp?
Check the ignition timing.
You have a very low restriction exhaust from the picture, it will be normal to have some popping but usually out of both sides.
Burning Brakes
Joined: Nov 2005
Posts: 832
Likes: 1
From: Breckenridge Colorado
Originally Posted by ahoover
You have a very low restriction exhaust from the picture, it will be normal to have some popping but usually out of both sides.
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Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Popping out the exhaust is most commonly a lean condition - not a rich condition or timing. The lean condition causes an occasional lean misfire, so the raw fuel from the lean misfire goes out the exhaust and then lights off. Try backing your idle mixture screws out a turn and see if it changes the problem. By installing that exhaust in place of the factory exhaust, you have leaned out the carb. If you have not re-jetted or re-set the carb up after changing the exhaust system, you are running very lean.
Instructor
Joined: Sep 2006
Posts: 192
Likes: 0
From: Fort Lauderdale FL
Don't know if this will help but since you mentioned right side only, do you still have the rams horn or stock manifolds? If so maybe the heat riser valve is popping due to changes in backpressure. If you still have the heat riser valve wire it open and see if that helps.
good luck
good luck
Safety Car
Joined: Dec 2004
Posts: 4,071
Likes: 0
From: San Diego CA
Originally Posted by lars
Popping out the exhaust is most commonly a lean condition - not a rich condition or timing. The lean condition causes an occasional lean misfire, so the raw fuel from the lean misfire goes out the exhaust and then lights off. Try backing your idle mixture screws out a turn and see if it changes the problem. By installing that exhaust in place of the factory exhaust, you have leaned out the carb. If you have not re-jetted or re-set the carb up after changing the exhaust system, you are running very lean.
I was about to post that but you beat me.
Racer
Joined: Feb 2005
Posts: 373
Likes: 1
From: Bayonne NJ
If it is only coming from one side of the exhaust it most likely is your valve adjustment.. Last week i had to drop my #8 piston an replace the rings.. After i reassembled it i tried to time it, i had the same problem.. after about an hour of trying this and still getting the popping you describe i called my local mechanic an he re-adjusted my valves.. no more popping.. The car runs amazing.. I would bet that this is your problem as well if it does it at idle
