popping in carb.....
Thread Starter
Burning Brakes
Joined: Dec 2004
Posts: 825
Likes: 0
From: Hanging out back with the dark horses. Wa.
popping in carb.....
Hello All,
Here is what I got. 81 350/350.. had the computer control but yarded all that and the smog. bolt on HP (header, edelbrock intake, and 1405 carb) HEI distrib, ect....
problem is that at high cruise mode- WOT it starts popping in the carb, almost a backfire. does it when she is at temp but not when you first take off. only does it under load.
fuel pressure is 5-6 psi at the carb. seems to run better with the timing way advanced 30*(I know this is bad too) choke is opening, idles fine. checked for vac leaks, valves are adjusted correct,
Here is what I was thinking
A) carb to lean? start playing with the needles and jets.
B) the stock computer cam is not maching to the intake and carb?
C) or I just dont know what Im doing
What do you guys think?
Here is what I got. 81 350/350.. had the computer control but yarded all that and the smog. bolt on HP (header, edelbrock intake, and 1405 carb) HEI distrib, ect....
problem is that at high cruise mode- WOT it starts popping in the carb, almost a backfire. does it when she is at temp but not when you first take off. only does it under load.
fuel pressure is 5-6 psi at the carb. seems to run better with the timing way advanced 30*(I know this is bad too) choke is opening, idles fine. checked for vac leaks, valves are adjusted correct,
Here is what I was thinking
A) carb to lean? start playing with the needles and jets.
B) the stock computer cam is not maching to the intake and carb?
C) or I just dont know what Im doing
What do you guys think?
Melting Slicks
Joined: Apr 2002
Posts: 2,337
Likes: 14
From: Norfolk VA
I would recheck timing first. When you set the timing did you use a dial back timing light? If not, try to your hands on one. These allow you to advance or retard degree by degree. The popping from the carb is definitely indicative of a lean condition. After that is done, then set the idle mixture screws. It is good to have a vacuum gauge handy when doing so.
Last edited by Oldguard 7; Jul 30, 2009 at 04:37 PM.
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
I would recheck timing first. When you set the timing did you use a dial back timing light? If not, try to your hands on one. These allow you to advance or retard degree by degree. The popping from the carb is definitely indicative of a lean condition. After that is done, then set the idle mixtures it is good to have a vacuum gauge handy when doing so.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Something in the secondary ignition could be breaking down. Cap rotor wires plugs. Module is pretty unlikely those either work or not. Check the leads from the pickup coil. They do break since they move everytime the vacuum advance does.
Having to run 30* initial advance might make me suspect the timing chain/gears might be headed south.
Having to run 30* initial advance might make me suspect the timing chain/gears might be headed south.
Thread Starter
Burning Brakes
Joined: Dec 2004
Posts: 825
Likes: 0
From: Hanging out back with the dark horses. Wa.
motor is fairly new maybe 10k. 30* int timing is way to much but runs better. HEI is a new summit one and checks out ok. does anybody think changing the metering rods or jet can fix this?, all parts are new. I have a holley 600 I will try next just to rule out the carb. if I set the timing at 14* she starts good but pops alot. I have another 81 w/ a 4spd and built motor and it runds great.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
If it is a single pop then its likely timing or mixture.
If it is is a series of pops that caries on until you back off the of the throttle, then I believe midyear is correct.
Last edited by DRIVESHAFT; Jul 31, 2009 at 08:47 PM.
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