HELP ! Backfires thru Carb
Thread Starter
Racer
Joined: Sep 2007
Posts: 383
Likes: 0
From: Roseville CA
St. Jude Donor '09
HELP ! Backfires thru Carb
So I had my 350 rebuilt. The engine builder dyno'd it ( I was there)
Ran great. He disconnected it from the dyno & loaded it in to my truck,
As I was installing it back in to my car I was careful NOT to mess with anything such as distributor, carb, timing etc.. All I did was connect the transmission & hooked up the exhaust.
I fired it up, wants to start but backfires thru the carb.
I checked for spark & fuel (Both good)
I assumed it is timing related so I rechecked the static timing by going TDC on #1 & the rotor was pointing towards #1 plug wire. I rechecked the firing order & it too is correct.
Refire.......same problem, backfires thru carb.
Am I missing something??
Ran great. He disconnected it from the dyno & loaded it in to my truck,
As I was installing it back in to my car I was careful NOT to mess with anything such as distributor, carb, timing etc.. All I did was connect the transmission & hooked up the exhaust.
I fired it up, wants to start but backfires thru the carb.
I checked for spark & fuel (Both good)
I assumed it is timing related so I rechecked the static timing by going TDC on #1 & the rotor was pointing towards #1 plug wire. I rechecked the firing order & it too is correct.
Refire.......same problem, backfires thru carb.
Am I missing something??
Thread Starter
Racer
Joined: Sep 2007
Posts: 383
Likes: 0
From: Roseville CA
St. Jude Donor '09
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Sounds to me like a vacuum line / port is not connected. Check them all for a vacuum leak, same thing happened to me with my new 427c I forgot to connect the pcv / brakes vacuum line at the manifold 
I think I am going to post this after all my posts. This is not aimed at the OP of this thread but I am tired of helping and getting no response once something has been fixed.
"Please report back what the problem was and how it was fixed
"
I think I am going to post this after all my posts. This is not aimed at the OP of this thread but I am tired of helping and getting no response once something has been fixed.
"Please report back what the problem was and how it was fixed
"
Last edited by MotorHead; Mar 15, 2011 at 11:47 AM.
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Army
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From: Butler Pa
Drifting
Joined: Aug 2005
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From: League City TX
Since you say the distributor wasnt removed, I bet it got bumped during transport or installation and changed the ignition timing.
That seems like the easiest thing to get out of whack between the dyno and your engine compartment.
That seems like the easiest thing to get out of whack between the dyno and your engine compartment.
Melting Slicks
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2024 C3 of the Year Finalist - Unmodified
Or the cap got bumped and it broke the rotor. Ask me how I know this.
Drifting
Joined: Nov 2006
Posts: 1,437
Likes: 6
From: Perth West Australia
St. Jude Donor '11-'12
Did you remember to hook up the bypass wire onto the starter solenoid?
Otherwise the engine cranks and tries to fire on 9volts which is not enough and as you let go of the key it backfires up through the carb.
Have a great day.
Kneel.
Otherwise the engine cranks and tries to fire on 9volts which is not enough and as you let go of the key it backfires up through the carb.
Have a great day.
Kneel.
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
Agree with a couple of posters above. My bet is, the distributor cap and/or rotor was cracked during transport,..easily done.
Second bet is the timing was diturbed. Perhaps the bracket that ties down the distributor wasn't fully tightened after you found optimum timing at the dyno.
Third bet is something in the valve train,..stuck valve, broken valve spring (how high did you rev this brand new mill?), etc.
Second bet is the timing was diturbed. Perhaps the bracket that ties down the distributor wasn't fully tightened after you found optimum timing at the dyno.
Third bet is something in the valve train,..stuck valve, broken valve spring (how high did you rev this brand new mill?), etc.
