I am having trouble with a new Holley 770 street avenger. The choke will get stuck open and not close when the truck sits overnight. So in the morning the fast idle came does not engage and the choke is wide open. I have noticed that this is caused by a small piece of red plastic behind the adjustable choke housing. I believe this is the fast idle cam? Either way, I can forcefully move that and get the choke to operate normally. Fast idle comes on and choke opens as it should. Next morning, though, rinse and repeat. Any ideas?
Also, im looking to really start tuning this thing. I want to learn a little more than the base adjustments and jet changes. I have an AFR gauge and vacuum gauge for tuning. Fairly good at reading plugs. I want to learn more about emulsion tubes etc. Any good source for this?
Thank yall in advance for any help!
Holley Street Avenger - choke stuck
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Schurkey
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Re: Holley Street Avenger - choke stuck
Of course. It's designed to work like that.
You must "Set The Choke" by tapping the gas pedal when the engine is cold. Typically, it doesn't take much movement of the gas pedal to get the choke to close. You only have to lift the fast idle screw high enough to clear the high step of the fast idle cam--enough gas pedal travel to equal about 2000 rpm with no load, more or less, depending on the fast idle speed, and how the engine responds to throttle when cold.
Tapping the gas also squirts a little fuel into the intake manifold, so it gets a "head start" on vaporizing. So as it gets colder, you need to tap the gas more, to squirt more fuel into the manifold. This assumes that there's fuel in the float bowl so the accelerator pump has fuel to squirt. No fuel, no squirt, hard starting. Thus folks adding an electric fuel pump to prime the carb after the vehicle has been unused for a day or three--enough time for the fuel urinated out of the gas station's pump to evaporate from the float bowl.
Point being, you need to calibrate your brain and coordinate your hand-and-foot movements depending on your vehicle's history and the ambient temperature. Most vehicles in good condition respond well to a tap of the gas pedal at every cold start, no matter how warm it is outside. At freezing, you may need 1/2 to 1 full tromp of the gas pedal. At 20 below zero, you may need two full pumps. But again, different carbs have different-sized accelerator pumps, and different engines respond to cold weather differently. You'll figure it out. THEN you turn the key to crank the engine.
Use the LEAST amount of gas-pedal pumping that results in a sure start. And the only way you'll know that is by experimenting.
AFTER the engine starts, you tap the gas pedal again--this lifts the fast idle screw off the fast idle cam, so that the fast idle cam rotates to the SECOND-highest step. Engine RPM drops a bit, and at that point you throw it in gear and cautiously drive off, keeping RPM and engine load moderate until the engine has fully warmed-up.
This is another of several reasons why electronic fuel injection--with temperature and throttle-position sensors; and computer-controlled idle speed--are so welcome in Today's World. With a carb and a choke system, you have to do some of the thinking that would otherwise be part of the computer routine.
For the record--I've never seen an aftermarket Holley carb that had the choke pulloff adjusted properly out-of-the-box. And Holley doesn't even give you the instructions for that when they sell an electric-choke housing. I had an article about choke adjustments written and hosted on another site, but they've removed it from view. Someday, I'll have to post it on my own web page.
AFTER you figure out the pump-before cranking procedure for your vehicle, expect to need to dick with the choke pulloff as the weather gets colder. Once the choke pulloff has been set properly for your engine, you may never need to mess with it again.
You must "Set The Choke" by tapping the gas pedal when the engine is cold. Typically, it doesn't take much movement of the gas pedal to get the choke to close. You only have to lift the fast idle screw high enough to clear the high step of the fast idle cam--enough gas pedal travel to equal about 2000 rpm with no load, more or less, depending on the fast idle speed, and how the engine responds to throttle when cold.
Tapping the gas also squirts a little fuel into the intake manifold, so it gets a "head start" on vaporizing. So as it gets colder, you need to tap the gas more, to squirt more fuel into the manifold. This assumes that there's fuel in the float bowl so the accelerator pump has fuel to squirt. No fuel, no squirt, hard starting. Thus folks adding an electric fuel pump to prime the carb after the vehicle has been unused for a day or three--enough time for the fuel urinated out of the gas station's pump to evaporate from the float bowl.
Point being, you need to calibrate your brain and coordinate your hand-and-foot movements depending on your vehicle's history and the ambient temperature. Most vehicles in good condition respond well to a tap of the gas pedal at every cold start, no matter how warm it is outside. At freezing, you may need 1/2 to 1 full tromp of the gas pedal. At 20 below zero, you may need two full pumps. But again, different carbs have different-sized accelerator pumps, and different engines respond to cold weather differently. You'll figure it out. THEN you turn the key to crank the engine.
Use the LEAST amount of gas-pedal pumping that results in a sure start. And the only way you'll know that is by experimenting.
AFTER the engine starts, you tap the gas pedal again--this lifts the fast idle screw off the fast idle cam, so that the fast idle cam rotates to the SECOND-highest step. Engine RPM drops a bit, and at that point you throw it in gear and cautiously drive off, keeping RPM and engine load moderate until the engine has fully warmed-up.
This is another of several reasons why electronic fuel injection--with temperature and throttle-position sensors; and computer-controlled idle speed--are so welcome in Today's World. With a carb and a choke system, you have to do some of the thinking that would otherwise be part of the computer routine.
For the record--I've never seen an aftermarket Holley carb that had the choke pulloff adjusted properly out-of-the-box. And Holley doesn't even give you the instructions for that when they sell an electric-choke housing. I had an article about choke adjustments written and hosted on another site, but they've removed it from view. Someday, I'll have to post it on my own web page.
AFTER you figure out the pump-before cranking procedure for your vehicle, expect to need to dick with the choke pulloff as the weather gets colder. Once the choke pulloff has been set properly for your engine, you may never need to mess with it again.
Last edited by Schurkey on Wed May 19, 2021 4:03 pm, edited 2 times in total.
Re: Holley Street Avenger - choke stuck
I just got a Holley 770 last Sunday and the choke does the same thing. I take and file the sides of the choke plate and no more sticking.
Re: Holley Street Avenger - choke stuck
I appreciate the wealth of information, as I hope it helps some folks. Unfortunately, I use that start procedure. A small amount of throttle pressure, and even a full pump of the pedal for that matter, does not close the choke as designed. I literally have to force it closed by forcefully pushing the red plastic arm in the direction of closing the choke. Once the chock is closed, all the starting procedure works great.Schurkey wrote: ↑Wed May 19, 2021 3:44 pm Of course. It's designed to work like that.
You must "Set The Choke" by tapping the gas pedal when the engine is cold. Typically, it doesn't take much movement of the gas pedal to get the choke to close. You only have to lift the fast idle screw high enough to clear the high step of the fast idle cam--enough gas pedal travel to equal about 2000 rpm with no load, more or less, depending on the fast idle speed, and how the engine responds to throttle when cold.
Tapping the gas also squirts a little fuel into the intake manifold, so it gets a "head start" on vaporizing. So as it gets colder, you need to tap the gas more, to squirt more fuel into the manifold. This assumes that there's fuel in the float bowl so the accelerator pump has fuel to squirt. No fuel, no squirt, hard starting. Thus folks adding an electric fuel pump to prime the carb after the vehicle has been unused for a day or three--enough time for the fuel urinated out of the gas station's pump to evaporate from the float bowl.
Point being, you need to calibrate your brain and coordinate your hand-and-foot movements depending on your vehicle's history and the ambient temperature. Most vehicles in good condition respond well to a tap of the gas pedal at every cold start, no matter how warm it is outside. At freezing, you may need 1/2 to 1 full tromp of the gas pedal. At 20 below zero, you may need two full pumps. But again, different carbs have different-sized accelerator pumps, and different engines respond to cold weather differently. You'll figure it out. THEN you turn the key to crank the engine.
Use the LEAST amount of gas-pedal pumping that results in a sure start. And the only way you'll know that is by experimenting.
AFTER the engine starts, you tap the gas pedal again--this lifts the fast idle screw off the fast idle cam, so that the fast idle cam rotates to the SECOND-highest step. Engine RPM drops a bit, and at that point you throw it in gear and cautiously drive off, keeping RPM and engine load moderate until the engine has fully warmed-up.
This is another of several reasons why electronic fuel injection--with temperature and throttle-position sensors; and computer-controlled idle speed--are so welcome in Today's World. With a carb and a choke system, you have to do some of the thinking that would otherwise be part of the computer routine.
For the record--I've never seen an aftermarket Holley carb that had the choke pulloff adjusted properly out-of-the-box. And Holley doesn't even give you the instructions for that when they sell an electric-choke housing. I had an article about choke adjustments written and hosted on another site, but they've removed it from view. Someday, I'll have to post it on my own web page.
AFTER you figure out the pump-before cranking procedure for your vehicle, expect to need to dick with the choke pulloff as the weather gets colder. Once the choke pulloff has been set properly for your engine, you may never need to mess with it again.
Re: Holley Street Avenger - choke stuck
Okay, little revision on the issue. I did find that when cold, I am able to hold the throttle just a hair open by hand, and then can easily move the red fast idle cam up or down. The problem I think i'm having is the choke is not "trying" to close when the truck is cold. Meaning there is no tension towards the close position from the electric choke. If memory serves me correctly, when the truck is cold, shouldn't the choke "spring" back closed if manually opening the choke valve by hand?
Re: Holley Street Avenger - choke stuck
It should spring back to the closed position, even if very slightly. If it had a choke pull-off, it'd have quite a bit more tension and the pull-off would overcome that as soon as it lit off and developed vacuum.
I'd first verify that the linkage isn't binding as 1980RS experienced. Remove the choke bimetallic spring cover and with the throttle cracked, all of the linkage should move free and easy. If anything binds, fix that first. Then reinstall the choke cover and adjust the choke to have a little tension closing the choke plate. The bimetallic strip in the coil needs to be stone cold to adjust, so verify that first.
I'd first verify that the linkage isn't binding as 1980RS experienced. Remove the choke bimetallic spring cover and with the throttle cracked, all of the linkage should move free and easy. If anything binds, fix that first. Then reinstall the choke cover and adjust the choke to have a little tension closing the choke plate. The bimetallic strip in the coil needs to be stone cold to adjust, so verify that first.
Re: Holley Street Avenger - choke stuck
The choke (spring tension preload) has to be adjusted for winter time temps and again for summer time temps to get it right.
When adjusted, the choke will not "set" unless you first step on the gas before starting. A single step on the gas is usually enough to "set the choke" when cold.
When adjusted, the choke will not "set" unless you first step on the gas before starting. A single step on the gas is usually enough to "set the choke" when cold.
Re: Holley Street Avenger - choke stuck
I figured it out. The choke wasn’t assembled correctly. The coil wasn’t attached to the tang on the choke arm. The coil wasn’t trying to close the choke and that’s what was causing the fast idle cam to stay in place and the choke to just stay fully open. Re assembled the choke correctly, now the choke valve moves with the adjuster, it closes when cold now with light throttle pressure.
Unfortunate to get a brand new part that was assembled incorrectly. I’m glad it was an easy fix, though!
Unfortunate to get a brand new part that was assembled incorrectly. I’m glad it was an easy fix, though!