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Author
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Topic: back Fire
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R&J MOTORSPORTS
Journeyman Posts: 73
From: Tampa,Fl.
Registered: Aug 2000
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posted 03-04-2002 09:58 PM
   
I have developed a back fire condition. 289 SS motor w/autolite 1.12 carb. I have rebuilt the carb. The motor runs up through the RPM's ok, but when let off the throttle, one quick back fire developes. Any ideas,thanx, Joe------------------
Joe Strunk
NHRA SS/MA 2890
1964 SS/MA Comet
1965 PRO-Street Fairlane
1966 Fairlane Conv.
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SteveLaRiviere
Administrator Posts: 32961
From: Saco, Maine
Registered: May 99
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posted 03-05-2002 07:50 AM
From the exhaust would mean excessive rich, like float levels too high or leaking needle&seats {did you remember the gaskets under the seats?}. From the intake would indicate excessive lean, like a vacuum leak.------------------
'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
MCA Member # 47773
Everyone needs to believe in something. I believe I'll have a beer!
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Moneymaker
Administrator Posts: 19686
From: Lyons, IL, USA
Registered: May 99
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posted 03-05-2002 12:06 PM
Stop trying to use nitro.  ------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link
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V8 Thumper
Gearhead Posts: 3366
From: Orange, Ca. United States of America
Registered: Dec 2001
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posted 03-05-2002 01:21 PM
quote:
Originally posted by Moneymaker:
Stop trying to use nitro.
ahem... you speak from experience? 
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Moneymaker
Administrator Posts: 19686
From: Lyons, IL, USA
Registered: May 99
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posted 03-05-2002 03:26 PM
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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link
IP: Logged |
70 Pony
Gearhead Posts: 1814
From: Glenmoore, PA, USA
Registered: Jan 2000
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posted 03-05-2002 05:15 PM
I had de-celeration backfires that drove me crazy...changed everything....then saw that with the Edelbrock Perf RPM intake , there was a vacuum port on the last runner on the passenger side.
I was using this for my Power Brakes (I THINK)...seems the vacuum was pulling air out of the port on deceleration, and I had what sounded like gunshots going off. Plugged the port, replumbed the vacuum lines...problem solved....
But check what Steve L said first...carburetion....and one thing I noticed (but I'm no mechanic)...if I advanced my timing a little the back firing would lessen but not completely go away.
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EDDIE D
Resto Mod '70 Sport Roof
Arrest Me Red
'02 GT, Torch Red
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R&J MOTORSPORTS
Journeyman Posts: 73
From: Tampa,Fl.
Registered: Aug 2000
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posted 03-07-2002 08:09 AM
I Found the problem. # 8 cylinder pushed the gasket out and I lost 1/2 of it. I guess the bolts backed out. I will have to check them more often. Alex, I took the car out to an 1/8 mile track (without Nitro) geeting ready for Orlando points meet (NHRA) the car went 7.11 and 7.07 at 94.63 mph. with 1.520 60'. This is the best I have ever gone. Looking foward to this weekend, should be good experience for me. ------------------
Joe Strunk
NHRA SS/MA 2890
1964 SS/MA Comet
1965 PRO-Street Fairlane
1966 Fairlane Conv.
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