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Holley Carb Issue/ Not my Vette

Old 10-22-2018, 05:47 AM
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scrappy76
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Default Holley Carb Issue/ Not my Vette

Just recently the My Holley carb just started loading up up idle. Sounds like I have a heavy cam, bit there is nothing but raw gas smell coming out of the exhaust. Once I start rolling and driving it runs great. To make sure it was the carb, I took it off and put on a space and she idled just fine like she is supposed to, so I know it's got to be the carb. I took it apart and blew out all the ports and used a tip cleaner thru everything I could. I put the carb back on the car yesterday and I thought it was fixed but it started doing it again. The float is adjusted correctly, where just a trickle comes out the side check screw. I can turn the air/fuel screws all the way in and out and it doesn't effect it. Like I said, once I start stepping on the pedal to go, she runs great. She revs up great, just idles for crap, loading up with gas.
Any ideas? Oh, I did rebuild the carb a couple months ago and she was running and idling great up untill now.
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Old 10-22-2018, 09:21 AM
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Originally Posted by scrappy76 View Post
Just recently the My Holley carb just started loading up up idle. Sounds like I have a heavy cam, bit there is nothing but raw gas smell coming out of the exhaust. Once I start rolling and driving it runs great. To make sure it was the carb, I took it off and put on a space and she idled just fine like she is supposed to, so I know it's got to be the carb. I took it apart and blew out all the ports and used a tip cleaner thru everything I could. I put the carb back on the car yesterday and I thought it was fixed but it started doing it again. The float is adjusted correctly, where just a trickle comes out the side check screw. I can turn the air/fuel screws all the way in and out and it doesn't effect it. Like I said, once I start stepping on the pedal to go, she runs great. She revs up great, just idles for crap, loading up with gas.
Any ideas? Oh, I did rebuild the carb a couple months ago and she was running and idling great up untill now.
needle & seat?
sticky float?

Last edited by pigfarmer; 10-22-2018 at 09:24 AM.
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Old 10-22-2018, 09:36 AM
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Originally Posted by pigfarmer View Post
needle & seat?
sticky float?


I had a Holley carb on a late 70s Pontiac T/A that I used to own, and had something similar happen. A piece of crud had somehow gotten into the fuel bowl, and eventually got stuck in the needle/seat assembly, causing the needle to not completely seat, and reduce the fuel flow at idle. It was "flooding" the car out, at idle.
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Old 10-22-2018, 06:42 PM
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Originally Posted by scrappy76 View Post
I can turn the air/fuel screws all the way in and out and it doesn't effect it.
If you turn the air/fuel mix screws in the engine is supposed to die. If it doesn't it's a blown power valve.

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Old 10-22-2018, 07:36 PM
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Originally Posted by pigfarmer View Post
needle & seat?
sticky float?
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Old 10-22-2018, 10:18 PM
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Power valve.
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Old 10-23-2018, 09:41 AM
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Both seem simple enough to check. I will take the needle and seat back out and clean and check for any dirt. If that doesn't solve the issue, I will change out the power valve and see if that solves the issue.
Thanks,
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Old 10-23-2018, 01:18 PM
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Originally Posted by scrappy76 View Post
Both seem simple enough to check. I will take the needle and seat back out and clean and check for any dirt. If that doesn't solve the issue, I will change out the power valve and see if that solves the issue.
Thanks,
If it turns out to be the power valve, you may want to consider installing an "anti-backfire valve" on the carb's power valve circuit, if it doesn't already have one
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Old 10-23-2018, 08:52 PM
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You may want to change out the needle and seat. The ethanol in todays gas eats away at the tip of the needle causing it not to seal as well.
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Old 10-23-2018, 09:52 PM
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Originally Posted by leadfoot4 View Post
If it turns out to be the power valve, you may want to consider installing an "anti-backfire valve" on the carb's power valve circuit, if it doesn't already have one
It would have to be a 1991 or earlier to not have that feature.
O---L---D. Really old.

Last edited by HeadsU.P.; 10-23-2018 at 09:54 PM.
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Old 10-24-2018, 10:26 AM
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Originally Posted by HeadsU.P. View Post
It would have to be a 1991 or earlier to not have that feature.
O---L---D. Really old.
I agree, but in the case of Holleys, there are literally MILLIONS of them out there, so you never know. The Holley that I had, I bought in the mid-80s, so it didn't initially have the anti-backfire valve, and I installed one. Having said that, I have to be honest....the last carburetor that I rebuilt was a Rochester Q-Jet, and IIRC, it was in 1993-94.
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Old 11-18-2018, 01:39 AM
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well I finally got around to changing the power valve and the needle seat set and she is still loading up bad at idle . I have to keep keep revving up the engine to keep it running or turn the idle screw way up. help. It has to be the carb because if I put a different one on she idles fine.
What should I try next ?
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Old 11-18-2018, 09:17 AM
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You say "loading up" which sounds like a flooding condition. However, if you have to rev it up to keep it running, perhaps its starving for fuel. At higher RPMs you are introducing even MORE fuel and it runs better.

By any chance when the carb was rebuilt, did you remove the Idle Mixture Screws? Was the gasket at the tip of that screw changed out? Did you accidently leave the old gasket on the metering block, then add another gasket on top of that?

Were the floats removed? Did you install the pin, spring and tab on the float correctly. You have a trickle of gas coming out of the sight hole, but you still are NOT 100% positive the float is even moving.

What makes one carb act this way and the other unit run fine? Are the vacuum lines hooked up identically both times? In other words is one carb receiving "ported" Vac and the other is getting "full" Vac? As you know, this will alter the timing characteristics at idle.

Keep at it. One day the solution will jump right out at you.
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Old 11-18-2018, 10:28 AM
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I would start over and rebuild the thing 100% .I had a similar problem with a really gummed up Edlebrock carb that I took apart 4 times before it would run correctly. ( I am a amateur and have bad eyesight). Easy to miss something. Any cracks? Gaskets correctly aligned. Gasket on the injector? Lower the float level so no gas comes out of the sight bowl?
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Old 11-18-2018, 11:45 AM
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Originally Posted by pltmgr View Post
I would start over and rebuild the thing 100% .I had a similar problem with a really gummed up Edlebrock carb that I took apart 4 times before it would run correctly. ( I am a amateur and have bad eyesight). Easy to miss something. Any cracks? Gaskets correctly aligned. Gasket on the injector? Lower the float level so no gas comes out of the sight bowl?

Yup I agree...^^^^^

Trying to hunt down the problem piece by piece at this point may not be the best approach if you are not very familiar with rebuilding the holley's which are super easy versus a Qjet. Just take it apart again and recheck everything doing a rebuild again......If it is a carb issue you will solve the problem......
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Old 11-18-2018, 12:04 PM
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Originally Posted by HeadsU.P. View Post
It would have to be a 1991 or earlier to not have that feature.
O---L---D. Really old.
Actually 1997.......I remember when they did it.....I was working at Gianino then......an old Holley R&D guy Randy Malik worked with us....I remember him saying why did it take so long!

Do not rule out the metering block gaskets........when the car is running at idle.....do you see fuel dribbling out of the boosters? Bad Power valve or metering gasket will cause this.

Jebby
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Old 11-18-2018, 03:03 PM
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pltmgr post just reminded me of a very common rebuild error on Holleys. The metering block gasket should only go on one way. But can easily be installed backwards.
If the gasket is 180* off, some fuel ports are blocked off. I believe YouTube has a video of the positioning of the gasket to match the holes correctly. Something to check into.
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Old 11-18-2018, 06:40 PM
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I bought the carb used. I bought a rebuild kit and rebuilt it. I installed it and the carb ran fine for a few months and then started having the idling problem, where it was too much gas at idle, eyes would burn from the gas fumes. it would run fine when I took off and drove it, just loaded up at idle. I thought it was the power valve and I also replaced the needle seat cause it seem to stick. I put it back on and it was actually worse then before. I read up on warping main bodies and metering blocks, so I took it back apart and took a file to the main body and it did have some low spots. I am now waiting for new gaskets. the other ones looked worn out from me taking the carb apart a few times.
So for the record, it was running fine after the rebuild, just started getting bad one day. I am thinking the new gaskets held for a short period but with the warpness, they justed started letting gas bleed by. We will see once the new gaskets come in. Also, the spare carb was hooked up just like the original, vacuum lines included.
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Old 11-18-2018, 07:29 PM
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Originally Posted by scrappy76 View Post
I bought the carb used. I bought a rebuild kit and rebuilt it. I installed it and the carb ran fine for a few months and then started having the idling problem, where it was too much gas at idle, eyes would burn from the gas fumes. it would run fine when I took off and drove it, just loaded up at idle. I thought it was the power valve and I also replaced the needle seat cause it seem to stick. I put it back on and it was actually worse then before. I read up on warping main bodies and metering blocks, so I took it back apart and took a file to the main body and it did have some low spots. I am now waiting for new gaskets. the other ones looked worn out from me taking the carb apart a few times.
So for the record, it was running fine after the rebuild, just started getting bad one day. I am thinking the new gaskets held for a short period but with the warpness, they justed started letting gas bleed by. We will see once the new gaskets come in. Also, the spare carb was hooked up just like the original, vacuum lines included.
If the gaskets dry out.....they will almost always leak....
donít kill yourself with the warp issue....the gasket can take care of it......just get good blue gaskets and replace them....your problem should disappear....

Jebby

Last edited by Jebbysan; 11-18-2018 at 07:29 PM.
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Old 11-18-2018, 07:45 PM
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Ok. Back to "flooding syndrome". Tell us about the floats. Primary & Secondary. Brass, Nitrophyl? Either one sometimes gets saturated and sink. Is the secondary float notched to clear jet extensions?

On the accelerator pump arm, is the gap between linkage and the arm 0.012 - 0.015 clearance, at WOT? If its too tight, you will get constant dripping into the venturie.

And last. Mechanical fuelpump or electric? Any reason the pump could have too much pressure? Is a regulator involved? Holleys are a little finicky about that.

Last edited by HeadsU.P.; 11-19-2018 at 08:27 PM.
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