Popping on decelleration
Thread Starter
Safety Car
Joined: May 1999
Posts: 4,445
Likes: 0
From: Mandeville, Louisiana
Popping on decelleration
Hey guys, some of you may know I am about to pull my motor in April to have it rebuilt, and stroked. I decided against the crate motor, and am going for more horse power.
In the meantime, when I am on the highway cruising at 60+ mph, and let off the gas completely, I get a pretty loud popping out of the pipes. It sounds like the right pipe, but I can't be sure. I just know its loud, and seems to be getting louder and worse.
I cannot find any exhaust leaks...all header bolts are tight with new gaskets. My timing is 8 degrees BTDC, idle speed is 750RPMS in park. This seems to have started after I had the carb rebuilt last September and just progressively got worse.
It also diesels on shut off occasionally; sounds like the motor is turning counter clockwise after the ignition is turned off.
Any ideas or input?
In the meantime, when I am on the highway cruising at 60+ mph, and let off the gas completely, I get a pretty loud popping out of the pipes. It sounds like the right pipe, but I can't be sure. I just know its loud, and seems to be getting louder and worse.
I cannot find any exhaust leaks...all header bolts are tight with new gaskets. My timing is 8 degrees BTDC, idle speed is 750RPMS in park. This seems to have started after I had the carb rebuilt last September and just progressively got worse.
It also diesels on shut off occasionally; sounds like the motor is turning counter clockwise after the ignition is turned off.
Any ideas or input?
Burning Brakes
Joined: Aug 1999
Posts: 774
Likes: 0
From: Palatine IL
Re: Popping on decelleration (Eric 70)
I had a similar problem and I corrected it by doing two things.
1) Set timing to 12 degrees BTDC.
2) Made sure the idle mixture screws on my Q-jet were adjusted correctly. I backed them until the highest rpm/vacuum and then turned them in a little and made sure both screws were backed out the exact same amount.
Good Luck.
1) Set timing to 12 degrees BTDC.
2) Made sure the idle mixture screws on my Q-jet were adjusted correctly. I backed them until the highest rpm/vacuum and then turned them in a little and made sure both screws were backed out the exact same amount.
Good Luck.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Popping on decelleration (Eric 70)
When flames shoot out of the exhaust pipe in race cars on deceleration in corners this is caused by improper idle mixture settings. The vacuum is pulling extra fuel into the motor. This could also be the cause for your popping. With a holley it can be the transfer slots open too far allowing fuel to be sucked through them.
