Backfiring
Thread Starter
Racer
Joined: May 2001
Posts: 270
Likes: 66
From: Bath, NY USA
Backfiring
Some of you may remember my recent post about my 66 surging when accelerating. Changing to larger jets and readjusting the mixture screws have taken most of that away, but it is backfiring very slightly when decelerating and sometimes when shifting now. It isn't a huge backfire, just slightly noticable. Does that sound like a timing issue? Timing is set at approx. 38 degrees total advance. Thanks!
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,271
Re: Backfiring (MasterDave)
Well, here I am. I think I covered the difference between backfiring and afterfiring and belching and farting in the other nearby thread on the same subject, however it might be educational to review the effect of the idle mixture screws for different carburetors, to wit:
The idle mixuture screws on the Carter AFB and Rochester WCFB control a fuel-air emulsion, so turning them in (CW) leans the mixture; turning them out (CCW) richens the misture.
My understanding is that the idle mixture screws on Holleys control an air only circuit, so turning the screws in (CW) richens the mixture and turning the screws out (CCW) leans the mixture - just the opposite of the AFB. Is this correct?
The Rochester FI system mixture screw also controls an air only circuit in the air meter, so the behavior of the mixture screw is as I stated for a Holley. Correct?
Duke
The idle mixuture screws on the Carter AFB and Rochester WCFB control a fuel-air emulsion, so turning them in (CW) leans the mixture; turning them out (CCW) richens the misture.
My understanding is that the idle mixture screws on Holleys control an air only circuit, so turning the screws in (CW) richens the mixture and turning the screws out (CCW) leans the mixture - just the opposite of the AFB. Is this correct?
The Rochester FI system mixture screw also controls an air only circuit in the air meter, so the behavior of the mixture screw is as I stated for a Holley. Correct?
Duke
Melting Slicks
Joined: Oct 2001
Posts: 2,740
Likes: 4
From: Marblehead MA
Re: Backfiring (SWCDuke)
Well, here I am. I think I covered the difference between backfiring and afterfiring and belching and farting in the other nearby thread on the same subject,
Duke
Duke
Let me get this straight .... is backfiring the same as farting.... or is it belching the same as afterfiring.... :confused: to wit: I am all confused..... to think I used to know this.... :yesnod: :crazy: :lol:
Supporting Vendor
Joined: Dec 2002
Posts: 548
Likes: 1
From: Woodstock GA
Re: Backfiring (SWCDuke)
i may need an independent confirmation on this from mr. bramlett, but,
on the '63 FI unit, there is the idle air circuit screw. screwing it in will eventually seat the screw and cut off the idle air (engine dies). the service manual says to start with it out 1.5 turns off the seat, then adjust as necessary. it works very well at getting decent idle characteristics.
there is also the idle speed screw which turns the bell crank opening the butterfly.
jerry, do i get a gold star if i got it correct?
on the '63 FI unit, there is the idle air circuit screw. screwing it in will eventually seat the screw and cut off the idle air (engine dies). the service manual says to start with it out 1.5 turns off the seat, then adjust as necessary. it works very well at getting decent idle characteristics.
there is also the idle speed screw which turns the bell crank opening the butterfly.
jerry, do i get a gold star if i got it correct?
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Race Director
Joined: May 2000
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Re: Backfiring (achapman)
Now, let's all get this straight. "Backfiring" through the carb is "belching' and "afterfiring" through the exhaust is "farting". :smash: :D
What could be more descriptive? :lol:
So the next time someone has one of these problems we will know what is meant by "belching orange fireballs out the carb", or "exhaust flatulence". :conehead
Duke
[Modified by SWCDuke, 9:28 PM 6/25/2003]
What could be more descriptive? :lol:
So the next time someone has one of these problems we will know what is meant by "belching orange fireballs out the carb", or "exhaust flatulence". :conehead
Duke
[Modified by SWCDuke, 9:28 PM 6/25/2003]