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| | | | Joined: May 2007 Posts: 1,718 Moderator: 60-66 Trucks; North Eastern Bolters | | Moderator: 60-66 Trucks; North Eastern Bolters Joined: May 2007 Posts: 1,718 | Had mufflers replaced on 62 283. Dual pipes. Stock setup with roch carb. Did not change anything except mufflers and short tailpipes. I picked up a backfire when I come off the excel pedal. Doesn't occur all the time but if I come off the pedal quickly it appears to be more frequent. Must be some science you all can teach me | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | If there is an air leak upstream, manifold, manifold to exhaust pipe, etc., there will be a backfire upon lifting the throttle.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | Try turning the idle jets out about 1/2 turn.
George
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Feb 2001 Posts: 1,094 'Bolter | | 'Bolter Joined: Feb 2001 Posts: 1,094 |
Tommy
59 apache 1/2t
261 short stepside
| | | | | Joined: May 2007 Posts: 1,718 Moderator: 60-66 Trucks; North Eastern Bolters | | Moderator: 60-66 Trucks; North Eastern Bolters Joined: May 2007 Posts: 1,718 | OK to all 3. I will work on it. Can I get a more specific comment and picture of the "idle jet"? Where is it and what does it do? | | | | | Joined: Feb 2004 Posts: 29,838 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,838 | The "idle jets" are the spring-stabilized screws at the base of the carburetor, AKA "idle mixture screws". 1/4 turn CCW will richen the mixture slightly at idle. Lean idle mixtures and/or late ignition timing has a tendency to backfire while coasting down to a stop in gear.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: May 2007 Posts: 1,718 Moderator: 60-66 Trucks; North Eastern Bolters | | Moderator: 60-66 Trucks; North Eastern Bolters Joined: May 2007 Posts: 1,718 | Thanks All. I will play with it some. | | | | | Joined: Mar 2010 Posts: 10,296 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,296 | Are your new mufflers less restrictive than the old ones?
If so, that might be why it did not backfire with the more restrictive old mufflers.
Tweaking the idle mixture screws sounds like a good idea to me. If that doesn't work, tweak the timing.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | I have had the same thing. It was as Ed says. Exhaust manifold leak. Exhaust leak. Those bolts do come loose.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
| | | | | Joined: May 2007 Posts: 1,718 Moderator: 60-66 Trucks; North Eastern Bolters | | Moderator: 60-66 Trucks; North Eastern Bolters Joined: May 2007 Posts: 1,718 | On the list. Thanks Carl and Bartamos for inputs. I do think the mufflers are different and are making a difference. I also may have those leaks somewhere. I will give it a go. | | | | | Joined: Jan 2014 Posts: 3,690 'Bolter | | 'Bolter Joined: Jan 2014 Posts: 3,690 | Shop vac (clean) set on reverse shoved in tailpipe. Wrap it tightly in a rag or something to get a decent seal. Turn it on and spray soapy water at the manifold or anywhere else you suspect a leak.
1951 3100
| | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | If you have never had duals before, they do rumble after deceleration. That's one of the reasons to have them 
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
| | | | | Joined: May 2007 Posts: 1,718 Moderator: 60-66 Trucks; North Eastern Bolters | | Moderator: 60-66 Trucks; North Eastern Bolters Joined: May 2007 Posts: 1,718 | Back to close out this question. While it took awhile for me to find my truck once I did, I richened up the mixture a hair and that took care it. Thanks for the lesson on carb adjustments.
Last edited by Hambone; 07/25/2021 10:26 PM.
| | | | | Joined: Nov 1995 Posts: 5,729 24601 | | 24601 Joined: Nov 1995 Posts: 5,729 | Thanks for closing the loop, Bone!
Always nice to get that feedback and close out the Yellow Sheet on a gripe.
JM
~ John A kid raised on Hotwheels, Matchbox and Tonka cannot be reasonably expected to own only one vehicle as an adult. 1949 Chevrolet 3804In the Legacy Gallery | In the Gallery Forum1973 IH 1310 Dump1963 Kaiser M38A12001 International/AmTran RE3000 "Skoolie"2014 Ford E-350 4x4 (Quigley) | | |
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