car chokes when given sudden throttle
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From: kissimmee fl
Car: 88 iroc-z z-28
Engine: 383
Transmission: th400
Axle/Gears: 3.42
car chokes when given sudden throttle
Hey guys i have a professionaly built holley 750. its been flowed to 925cfm and it a true double pump.
Im trying to figure out why my car is choking off the line at the track.
If i just punch at the pedal it wants to die. Im not sure if my accelator springs are too tight or too loose. Who knows if thats even the problem.
What else could it be?
Im trying to figure out why my car is choking off the line at the track.
If i just punch at the pedal it wants to die. Im not sure if my accelator springs are too tight or too loose. Who knows if thats even the problem.
What else could it be?
Joined: Mar 2000
Posts: 43,187
Likes: 43
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
That's not "choking", that's "bogging".
It's a lean condition. It doesn't have anything to do with the accelerator springs (at least, certainly shouldn't if the carb was "professionaly built" - did you fiddle with them after they put it together?). You aren't getting a sufficient accelerator pump shot, which means the mixture is going to be lean until the main fuel circuits can catch up.
It also doesn't have anything to do with fuel pressure. Fuel pressure merely fills the fuel bowls, it doesn't directly affect lean or rich. However, float level could affect you, so verify the fuel bowls are being filled to the proper level.
"Professionally building" a 750 so it flows 925 CFM is a stretch. You can do that by fudging a few things, like the vacuum level at which you measure the flow (although I doubt they actually did a flow test on it), but I'd be very suspicious of anyone who claims they modified a 750 to flow 925 CFM. Did they give you a build sheet? Do you have information such as jet sizes, power valve #'s, accelerator pump volume, squirter size, air bleed modifications, etc.?
It's a lean condition. It doesn't have anything to do with the accelerator springs (at least, certainly shouldn't if the carb was "professionaly built" - did you fiddle with them after they put it together?). You aren't getting a sufficient accelerator pump shot, which means the mixture is going to be lean until the main fuel circuits can catch up.
It also doesn't have anything to do with fuel pressure. Fuel pressure merely fills the fuel bowls, it doesn't directly affect lean or rich. However, float level could affect you, so verify the fuel bowls are being filled to the proper level.
"Professionally building" a 750 so it flows 925 CFM is a stretch. You can do that by fudging a few things, like the vacuum level at which you measure the flow (although I doubt they actually did a flow test on it), but I'd be very suspicious of anyone who claims they modified a 750 to flow 925 CFM. Did they give you a build sheet? Do you have information such as jet sizes, power valve #'s, accelerator pump volume, squirter size, air bleed modifications, etc.?
Thread Starter
Supreme Member
iTrader: (8)
Joined: Dec 2004
Posts: 1,153
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From: kissimmee fl
Car: 88 iroc-z z-28
Engine: 383
Transmission: th400
Axle/Gears: 3.42
Re: car chokes when given sudden throttle
That's not "choking", that's "bogging".
It's a lean condition. It doesn't have anything to do with the accelerator springs (at least, certainly shouldn't if the carb was "professionaly built" - did you fiddle with them after they put it together?). You aren't getting a sufficient accelerator pump shot, which means the mixture is going to be lean until the main fuel circuits can catch up.
It also doesn't have anything to do with fuel pressure. Fuel pressure merely fills the fuel bowls, it doesn't directly affect lean or rich. However, float level could affect you, so verify the fuel bowls are being filled to the proper level.
"Professionally building" a 750 so it flows 925 CFM is a stretch. You can do that by fudging a few things, like the vacuum level at which you measure the flow (although I doubt they actually did a flow test on it), but I'd be very suspicious of anyone who claims they modified a 750 to flow 925 CFM. Did they give you a build sheet? Do you have information such as jet sizes, power valve #'s, accelerator pump volume, squirter size, air bleed modifications, etc.?
It's a lean condition. It doesn't have anything to do with the accelerator springs (at least, certainly shouldn't if the carb was "professionaly built" - did you fiddle with them after they put it together?). You aren't getting a sufficient accelerator pump shot, which means the mixture is going to be lean until the main fuel circuits can catch up.
It also doesn't have anything to do with fuel pressure. Fuel pressure merely fills the fuel bowls, it doesn't directly affect lean or rich. However, float level could affect you, so verify the fuel bowls are being filled to the proper level.
"Professionally building" a 750 so it flows 925 CFM is a stretch. You can do that by fudging a few things, like the vacuum level at which you measure the flow (although I doubt they actually did a flow test on it), but I'd be very suspicious of anyone who claims they modified a 750 to flow 925 CFM. Did they give you a build sheet? Do you have information such as jet sizes, power valve #'s, accelerator pump volume, squirter size, air bleed modifications, etc.?
Alright ya the i changed an intake from the rpm air ap to a vitctor. so we changed the a/f screws and i think myaccel pump springs are of some.
They gave me a build sheet and everything.
Its a 900 dollar carb, i get perfect gas mileage and literally gained hp just from swapping it. they bored out the carb some too and all.
They have 80's all around for jetting whch they gave me 78's originally
Joined: Mar 2000
Posts: 43,187
Likes: 43
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
No power valves, or PV's both primary and secondary?
What size are the accelerator pumps and squirters?
Are you running a Victor or Victor Jr.? Single plain intakes will reduce the vacuum signal to the carb, requiring more accelerator shot to make up for it. Did this only start after the intake change? You may also have a vacuum leak.
What size are the accelerator pumps and squirters?
Are you running a Victor or Victor Jr.? Single plain intakes will reduce the vacuum signal to the carb, requiring more accelerator shot to make up for it. Did this only start after the intake change? You may also have a vacuum leak.
Thread Starter
Supreme Member
iTrader: (8)
Joined: Dec 2004
Posts: 1,153
Likes: 0
From: kissimmee fl
Car: 88 iroc-z z-28
Engine: 383
Transmission: th400
Axle/Gears: 3.42
Re: car chokes when given sudden throttle
tested for vacuum leaks. none.
what im figuring is either bigger squirters or i need better accelerator pump cams
Vic jr.
what im figuring is either bigger squirters or i need better accelerator pump cams
Vic jr.
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