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I have a pretty new Holley 770 Avenger carb that is giving me a problem. After the car warms, sometimes at idle, the car will just die. If you give it a little gas ( 200-300 RPM, the motor will run fine), other wise it acts like you just kill the switch and dies. It will fire right back up and run fine, the problem is ONLY @ IDLE, and not all the time.
Thoughts?
 

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spray some carb cleaner around the base of the carb while its running to see if the rpms pick up! if they do you might have a bad gasket or warped base on the carb!! thats on thing to check!!
 

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Mark,
When you get it all figured out, dialed-in and had a chance to run the car...I am looking at purchasing the same carb and would be very interested in hearing how you like the new carb. Also, I was wondering which model you have. I am looking at the 80770 and 83670. They are the same carbs except the 83670 is aluminum with a vibratory polish finish. Thanks in advance.
 

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I chased the same problem when I was getting my 670 Street Avenger set up. It sounds like the idle mixture may need to be tuned some and you may need your ignition timing tweaked. I know they say they're set up for most applications "right out of the box" but don't rely on that. My mixture screws were too far in.

First off, make sure your timing is set correctly. I'd say around 14-16 degrees initial unless you know for sure what your motor likes and how much mechanical advance you've got built into your distributor. Then make sure that you have a good set of double return springs on the throttle so that it is seated all the way at idle and make sure your accelerator arm is not hitting the back of the valve cover.

If your cam allows it and you can get it idling around 700-800, put a vacuum gauge on the small port just underneath the front passenger side edge. Don't use the upper small port as that one is not full manifold vacuum and will only give you a reading with the throttle open. Now use a small flathead screwdriver and turn one idle mixture screw out a small amount at a time (eighth turn) and see if your vacuum reading goes up. If so, turn out the other side the same amount. Go back and forth until the vacuum stops going up. You may also need to adjust your idle screw while doing this to maintain idle. If you don't have a wideband AFR monitoring setup, this is about the best you can do to get the idle mixture set. Also, if you turn it out at some point and don't see the vacuum change, turn it back to where it was.

BEFORE you do that above, you may need to make sure that both idle mixture screws are set the same beforehand. They are supposed to be but you never know. Start with one and turn it all the way in while keeping an accurate count of how much. It will probably only be about 3/4 turn. Then turn it back out to where it was initially and do the same to the other screw making sure that they are both out the same amount.

That's the only thing I've had to do with mine so far. I'm sure it could use some tweaking but the car is running good and the plugs are showing brown/tan.

Oh yeah, and the vacuum gauge reading should be fairly steady. If it's not, that'll point to other issues. They carry a nifty little one with rubber tube attached at most parts stores.
 

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I chased the same problem when I was getting my 670 Street Avenger set up. It sounds like the idle mixture may need to be tuned some and you may need your ignition timing tweaked. I know they say they're set up for most applications "right out of the box" but don't rely on that. My mixture screws were too far in.

First off, make sure your timing is set correctly. I'd say around 14-16 degrees initial unless you know for sure what your motor likes and how much mechanical advance you've got built into your distributor. Then make sure that you have a good set of double return springs on the throttle so that it is seated all the way at idle and make sure your accelerator arm is not hitting the back of the valve cover.

If your cam allows it and you can get it idling around 700-800, put a vacuum gauge on the small port just underneath the front passenger side edge. Don't use the upper small port as that one is not full manifold vacuum and will only give you a reading with the throttle open. Now use a small flathead screwdriver and turn one idle mixture screw out a small amount at a time (eighth turn) and see if your vacuum reading goes up. If so, turn out the other side the same amount. Go back and forth until the vacuum stops going up. You may also need to adjust your idle screw while doing this to maintain idle. If you don't have a wideband AFR monitoring setup, this is about the best you can do to get the idle mixture set. Also, if you turn it out at some point and don't see the vacuum change, turn it back to where it was.

BEFORE you do that above, you may need to make sure that both idle mixture screws are set the same beforehand. They are supposed to be but you never know. Start with one and turn it all the way in while keeping an accurate count of how much. It will probably only be about 3/4 turn. Then turn it back out to where it was initially and do the same to the other screw making sure that they are both out the same amount.

That's the only thing I've had to do with mine so far. I'm sure it could use some tweaking but the car is running good and the plugs are showing brown/tan.

Oh yeah, and the vacuum gauge reading should be fairly steady. If it's not, that'll point to other issues. They carry a nifty little one with rubber tube attached at most parts stores.
Do as he states and make sure you fix any vacumm leaks. I run the 770 Avenger and after setting it up as stated above I have no issues with mine and I like the way the car runs with it, mine has the electric choke and is not the new lighter one. :yes:
 

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I chased the same problem when I was getting my 670 Street Avenger set up. It sounds like the idle mixture may need to be tuned some and you may need your ignition timing tweaked. I know they say they're set up for most applications "right out of the box" but don't rely on that. My mixture screws were too far in.

First off, make sure your timing is set correctly. I'd say around 14-16 degrees initial unless you know for sure what your motor likes and how much mechanical advance you've got built into your distributor. Then make sure that you have a good set of double return springs on the throttle so that it is seated all the way at idle and make sure your accelerator arm is not hitting the back of the valve cover.

If your cam allows it and you can get it idling around 700-800, put a vacuum gauge on the small port just underneath the front passenger side edge. Don't use the upper small port as that one is not full manifold vacuum and will only give you a reading with the throttle open. Now use a small flathead screwdriver and turn one idle mixture screw out a small amount at a time (eighth turn) and see if your vacuum reading goes up. If so, turn out the other side the same amount. Go back and forth until the vacuum stops going up. You may also need to adjust your idle screw while doing this to maintain idle. If you don't have a wideband AFR monitoring setup, this is about the best you can do to get the idle mixture set. Also, if you turn it out at some point and don't see the vacuum change, turn it back to where it was.

BEFORE you do that above, you may need to make sure that both idle mixture screws are set the same beforehand. They are supposed to be but you never know. Start with one and turn it all the way in while keeping an accurate count of how much. It will probably only be about 3/4 turn. Then turn it back out to where it was initially and do the same to the other screw making sure that they are both out the same amount.

That's the only thing I've had to do with mine so far. I'm sure it could use some tweaking but the car is running good and the plugs are showing brown/tan.

Oh yeah, and the vacuum gauge reading should be fairly steady. If it's not, that'll point to other issues. They carry a nifty little one with rubber tube attached at most parts stores.
To confirm: If you are adjusting the idle mixture screws and have a vacuum gauge hooked up to full manifold vacuum at the base of the carb, should it be teed into that connector so you can run full manifold vacuum to the vac advance while you're adjusting the idle mixture screws?
 

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To confirm: If you are adjusting the idle mixture screws and have a vacuum gauge hooked up to full manifold vacuum at the base of the carb, should it be teed into that connector so you can run full manifold vacuum to the vac advance while you're adjusting the idle mixture screws?
Yes, if you are running that for your vacumm advance, t into the line just as you said. That is what I did when I set mine.
 

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Yes, if you are running that for your vacumm advance, t into the line just as you said. That is what I did when I set mine.
That makes sense. Because last night I was double-checking timing and adjusting the carburetor and I was wondering why I was only pulling 9-10" Hg. But, now I realize that I had the vacuum gauge hooked up to full manifold vacuum which is where my vac advance normally goes. So I guess I was pulling 9-10" Hg at idle with only initial timing of about 16°.

Now I need to go get a $30 dial-back light so I can more easily check timing, adjust my mechanical advance if necessary, etc.

I have the 670 Al Street Avenger and other than a cold-start choke (electric) issue (won't fast idle and so stalls, lightly backfires, and is rough until warmed up...) which I need to play around with and a VERY slight throttle tip-in hesitation, I love the carb. I'm sure I will have more comments once my engine is broken in and I can step on it a bit more... I don't think I have even gotten into the secondaries yet... maybe... :)

I don't mean to hi-jack the thread - just wanted to add a few comments...
 

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Jeff,

I run my vacuum advance on the ported vacuum port so vacuum advance only comes in with the throttle open right now. There are proponents for both but mine seems to run pretty good like this. With the MSD HEI, I've got 20 degrees of mechanical advance so I just set my initial at 16 to give me 36 degrees total. I wouldn't bother with a dial back light.....just hold onto one of the little rubber caps that came on the ports to plug it and then plug your vacuum can line when you want to check/set your timing.

When I first installed the SA, I was only pulling 8" at idle and was able to get it up to 12" without doing any timing changes or bumping the idle up. If your idle goes up, vacuum is going to go up as well.

As for your choke, it should be fairly easy to figure out. I'm running the 12V from my windshield wiper motor feed line and it does well. Any key-switched 12V point should do fine. I didn't change any of the choke settings (fast idle, choke timing). It's pretty much one pedal pump, hit the key, and it fires right up and runs up to 1600 RPM.
 

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Don't get the dial-back timing light...If you research those on here most guys will advise against them. Get yourself some timing tape and install it on the balancer. It's a $7 solution that’s guaranteed to be accurate.
 

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Steiner - I too have my choke wired to the windshield wiper motor along with my tach. I hadn't messed with the choke since a couple days ago when I found that the timing was far too advanced. Right now I have it at 16° initial. This morning I fired it up and after a minute or so keeping it around 1500RPM, I let it settle into its idle around 800RPM. I removed the air cleaner and adjusted the choke CCW and that got the plate to close a bit. It was much smoother this morning as a result; just one little pop when I was turning a corner in second gear, but it didn't stall out. Maybe one or two more notches CCW and the choke should be fine.

Now I just need to decide on which headers since the cam is broken in and my driver's side exhaust manifold has a crack/leak in it... good excuse to get headers :)
 

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Regarding the dial-back light... are they not very accurate? Well... my new balancer is degreed up to 50, so maybe I will just make a couple easy-to-spot white-out marks at 16° and 36° and use my current light...
 

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Regarding the dial-back light... are they not very accurate? Well... my new balancer is degreed up to 50, so maybe I will just make a couple easy-to-spot white-out marks at 16° and 36° and use my current light...

That's about the best thing to do.

Also regarding your choke....once you feel the car is warmed up enough you can just rev the gas one time at idle and the choke will pull off. Turning the choke body just changes the amount of time that the choke stays in on its own but you already know that. I always just rev mine to get the choke to pull off. Unless you've got five minutes or so to let it sit and warm up for perfect takeoff right out of the driveway , there's no better way to get the car going once it'll hold idle than to just go ahead and put a load on it and let it burp and fart for a quarter mile if it wants to.

If you pump the gas once or twice before you start it you may find it fires up easier cold. It puts a shot of fuel in the intake.
 
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