New Holley carb won't idle down...

Mikesbaron

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I purchased a new Holley FR-80457SA 600 CFM Street Warrior Carburetor and installed on my 1979 with a Ford Crate 302. I hooked the e-choke up to a 12v ignition source.
The car starts up fine but idles at 1800 RPM, and then every few seconds continues to idle up to and past 3000 rpm! It does this whether I have the throttle cable connected or not. If I blip the throttle it does nothing to idle it down. I've tried adjusting the curb and fast idle screw but it has no effect. The only way I can get the idle down to 1200-1400 is if I manual close the choke plate while it's idling.

I have a new carb to manifold gasket and no vacuum leaks that I can tell. I hooked up the distributor to side of carb vacuum line, and then the two additional vacuum spigots on the lower front of the carb I left capped (as I have no other lines from my car or old carb that hooked into anything else.)

I've been on the phone and via back and forth email with Holley tech support and tried the above idle adjustments with no solution. Can anyone give me some help on this thing?
 
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CarMichael Angelo

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You either have a defective carb, ( twisted shaft) or a vacuum leak as a result of a warped base plate, a bad base plate gasket, or a missing vacuum plug. Are you hooking the big vacuum plug that goes to either Power brake booster, or PCV at the rear base of the carb? If you are, unhook that hose, and plug that off to eliminate that potential leak point.
 

Mikesbaron

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I'll check that plug at the bag of the carb and make sure it's capped. My intake manifold has a threaded multi prong spigot that my brake vacuum hose is running off. In this picture I htink you're talking about the black plug on the lower right? I have the other two on the left (front of carb) still plugged off. And then my distributer vacuum line is going to the spigot just to the upper right of the choke in this pic.
 

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7991LXnSHO

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Are you sure the throttle linkage or cable is letting the bracket on the primary shaft to close all the way?
Are the secondaries also closed all the way? I have experienced what happens when the closing link between the primaries and vacuum secondaries is bent to open both sides like a double pumper. If it was bent a bit in shipping or was off at the factory, these type of symptoms are possible.
 

Mikesbaron

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I know the primary shaft is closing all the way because I've manipulated it with and without the throttle linkage attached and it has no effect on the idle speed-the only thing that seems to affect idle speed is the choke plate, which continues to open little by little every few seconds that the car idles (as it warms up.)

I'm not sure what the closing link between primaries and vacuum secondaries is, but I'll look at and mess with it again to see if I can detect any bends-though I can tell you I haven't seen anything oddly out of shape on any of the linkages or arms.

I keep hearing about resetting the choke cam (red plastic cam) by pushing the throttle linkage to the open position. When I push throttle linkage to open position and trying to manipulate the choke cam, I'm not getting any type of reset. Matter of fact, I can't even see how it would reset to any position other than the one it is in.
 

Mikesbaron

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Here is pic showing the large vacuum hose hooked up to the spigot coming out from the back of the carb, just as I had on the previous carb.
cable5.jpg
 

7991LXnSHO

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ED7C6C60-221E-44F4-8D82-5AC93A7DCD53.jpeg

Please take a close picture of the linkages on the side of the carb where the arrow is pointing to off the edge of the photo and I can show you. My Holley powered car is still winterized off site.
 

Mikesbaron

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I verified that the secondaries (the two small valves on the other side of the carb-not under the choke valve) are closed. I also verified that the red choke cam is in the proper position, depending on whether the choke plate is open or closed. Choke plate closed its up and choke plate open its down.

Will this pic suffice for you to point out where something might be bent?

Also, here is a pic of the carb I took off the carb. Notice how the choke plate was zip tied open. The car seemed to run and idle fine, just had to tap it a few times in the morning to get it to work without choke plate. Could that indicate anything I might be overlooking tied to the current high rpm problem?

Regarding vacuum leaks, here is what I've done:
1. Removed brake booster vacuum line and plugged it= no change, still have high rpm that climbs all the way from 1600 at start up to over 3000 rpm if I don't shut car off.
2. Removed large vacuum plug on lower front of carb=the already high rpms took off and started climbing really quickly. I could feel very strong suction on that spigot, so I capped it back off again.

Where else might it be leaking vacuum? You mention base plate. Is that simply the bottom flat part of the carb? Where else should I be checking?
 

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Mikesbaron

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This is a remanufactered (by Holley) carb I purchased directly from Holley.

I have tried adjusting the fast idle screw in and out to ZERO affect. I've also done this for the CURB idle screw. The ONLY thing to have any effect is closing the choke plate.

If you mean the base gasket, as in the gasket between the carb and intake manifold, it is the new Holley gasket they included with the kit.
 
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General karthief

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I suspect you have a large vacuum leak under the carb.
I need to see the bottom of the carb, the carb flange on the intake and the gasket used, please.
 

90sickfox

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Have you adjusted the choke ? Loosening the three screws should allow you to rotate it to decrease rpm.

View: https://youtu.be/0H5IBSFgYJE


Vacuum leaks will cause a similar issue....like Mike said. Most people don't even use the choke.
 

7991LXnSHO

wanna catch the space herp
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Have you adjusted the choke ? Loosening the three screws should allow you to rotate it to decrease rpm.

View: https://youtu.be/0H5IBSFgYJE


Vacuum leaks will cause a similar issue....like Mike said. Most people don't even use the choke.
Not using a choke in Utah would be rough.
Do you have the vac advance for the distributor connected to ported vacuum or manifold vac? If it’s advancing timing at idle instead of RPM, that will be a problem.

I think you will find a vac leak, but these are other things to check for.
The link end I circled is for closing the secondaries. It’s the one some fools bend to open the secondaries (instead of close them). Then the secondaries open and can stay open. (Whee!) I will stop by my carburetor powered car to see if that much gap looks right and if the link is in the right hole on the same model. You say you are sure they are closed all the way, but air is getting in somewhere. So let’s rule it out.

If closing the choke flap all the way slows down the stupid high idle, it still sounds like the primary butterflies are open too far. When you check the base gasket, inspect the bottom of the carb to make sure they are closing as far as you think and the gasket has not been interfering.


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Mikesbaron

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1. I have the vac advance for the distributor going to the side carb spigot on the back rightside of the carb, just as it was connected on my old carb (it had mechanical secondaries). Should I try it in a different port or disconnect it altogether to see what happens?

2. You said to check to see if "the primary butterflies are open too far", are these the butterflies that lie under the choke plate side of the carb? With the secondaries being the non choke plate side of the carb, the one you marked in the photo. I'll also see if I can manually push the secondaries lever to the "closed" position and see if that does anything while the car is started up, before I remove the carb to inspect.

3. Should I put the old carb back on and see if anything changes? I didn't have this high idle issues until I tried to swap carbs and gasket.

Thanks for all the help.
 

7991LXnSHO

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1. The carb should have come with instructions that labeled what port is what.
Do you have a vac gauge? Ported vac generally will be little at idle and go up with rpm. The manifold vac will be highest at idle and will drop with a rapid opening of the throttle.
Do you have a timing light to see what the timing is with the hose disconnected and blocked vs. connected at idle and at higher Rpm’s?
2. The butterflies are the (brass) discs at the bottom of the carb, (in this case in the bottom carb plate), that open to allow air and atomized gas into the engine. They are inserted through slots in the throttle shafts. The primary is connected to the throttle linkage or cable, and the secondaries are vacuum opened with that link to help them close.
3. Why did you pull the old carb? This is simpler than fuel injection.
 

Mikesbaron

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No I don't have a timing light or vacuum gauge.
I pulled the old carb off because it was too big, 750cfm, and it had a bad bog in the low and mid. Plus look at how the TV and throttle cable bracket were held in place. It would slip in gear at high rpm if I gassed it (mal adjusted...obviously) TV cable. I had no history or trust in the carb, no telling when it was last cleaned, or rebuilt. And it was suggested that the proper cfm carb would help me run without the bogs, that vacuum operated secondaries would be best for a street car.
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7991LXnSHO

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The new carb is a better fit. Go with the diagnostics and figure it out.
Did you check float levels?