How to adjust Holley Idle Mixture Screws and Curb Idle 

Thank you!! :)

@@AndyKruseChannel now if I could just figure out how to use my timing light.....🙄

@@rorschach8167 💡?😳

Thanks for the tip!

I had a brand new out of the box 4160 that wasn't getting fuel in the bowels. My buddy "the brains" adjusted the float levels until fuel was just coming out of the holes (no site glass on mine). That did the trick for us. The paperwork will tell you if its just to the bottom or half way up the site glass. I'm a noob and sharing what I learned.

Awesome, glad I can help! :)

Yeah, these are fun to work on. :)

You and me both!

Yes, this is a good option. :)

Yeah cause they still make them that way lol

​@@AndyKruseChannelukssssp❤😂😂😂😂😢🎉😢😅

Thanks for the heads up.

Awesome! :)

Thanks! :)

No problem 👍

Thanks for the info!

@@AndyKruseChannel I am sure you already knew that about the Accelerator pump arm Andy, The info was more for the shade tree mechanics, lol Excellent video on your part sir.

Haha, it took me a second to understand what you meant by a Baker. Sometimes I'm a little slower than I should be. Welcome to the club! :)

Awesome, I’m glad I can help. 🙂

Glad it helped

Good to know.

Ok

Yep, good advice.

It goes on the port located below the front bowl. This is the manifold vacuum port. :)

Yes

Thanks for the heads up.

@@russzero Another measure you can take before drilling holes is to crack open the secondaries a little bit. Holleys have an adjustment accessible from the underside of the carb.

​@@AndyKruseChannelwhere do I hook up my vacuum gauge at I might have to re watch where you put it or nvm I think I see it I have my PVC valve hooked up in the back is that where you have the gauge

​@@AndyKruseChannelso yeah I don't think I'm seeing that correctly if you could help me out I'd appreciate it

@@Pdubb19 I prefer to use the Manifold Vacuum Port, on these Holley carbs is located under the front bowl. I point it out at around 2:11 :)

Thanks 👍

Ideally they'd be the same, but it depends on how exacting you want to be when adjusting for the highest vacuum. :)

I think the idea is to not have it heavier or richer to one side of the bank. To keep all 4 the same and the highest vacuum you can start using 1/8 increments or even 1/16th to really keep that same highest vacuum and keeping all screws equal. Just going by what Holley says.

Hmmm, that's weird, there should be one. What about using the port on the back of the carb that is often used for a PCV valve or power assisted brake master cylinder? It's larger than the port I use in this video, you'd probably need 1/4" or 3/8" tubing and an adapter to make it work with your vacuum gauge. :)

Coming soon. :)

Backing the screw out away from the Carb is adding fuel, equaling a richer condition.

Unfortunately it could be one of several things. The jets could be too large for your application. The accelerator nozzles too large. The cam for the accelerator needs to be sized correctly. Maybe the float inside the fuel bowls is letting in too much fuel. Possible the idle mixture screws still need to be adjusted. It's tough to tell with being there, but thankfully there seems to be a video on RU-vid for every scenario. :)

Cool, glad I could help you. :)

At the time I made this video, I had not re-lashed my valves. Yes, it was sort of a sewing maching sound, and I had found out I had one that was not as tight as the rest. I re-lashed them and the engine sounds much better. :)

It depends on the climate. Warmer climate cars can get by w/o a choke. In colder climate, it takes a little more effort to get the car to idle, but it can be done. Holley makes a choke kit you can buy and attach to your carb if you think you need one.

I think there was a problem with the gauge at the time, because it was leaking. It's between 4-6 psi now.

Good deal. love your videos 👍🏻

My pleasure!

Yep. :)

You got this!!

Correct, but this is ok because that vacuum advance on your distributor isn't really doing anything until you are operating at higher RPMs and have a load on the engine. The hose going to your vacuum advance on the distributor can just sit there while you make your adjustments. On the carb, for setting the idle mixture screws, you'll want to make sure the Ported port on the carb is capped off (up by the sight window on the bowl) and you connect your vacuum gauge to the manifold port located underneath the front bowl. :)

That just means you're making too much power! :)

There's a lot more to dialing in the Carb than doing a 1/4 turn, so it'll take a few more videos pointing out all the things you need to check. Also, the comment section of a RU-vid video is not really the best place to have a discussion about how to tune your Carb. :)

It's not about an optimum setting, just the highest value you can read.

Wow, there's a lot to unpack here. Without knowing the displacement of your motor, it's difficult to say if the 750 is the right carb for you. In addition to the displacement, your Cam, intake style, heads, and exhaust can also play a role in the proper Carb size. In my case, I'm at the very bottom edge of needing a 750, and a 670 would probably be a better Carb for me. Anyways, you can use this video to help you dial in your best-lean-idle settings with your mixture screws, and lowering the idle from 2300 down to a more useable 750-900 rpm. You may also need to worry about the throttle plate setting with respect to your transfer slot, but I don't cover that part in this video. But adjusting all that stuff may be a waste of time if you've got large jets and different power valve than the stock pieces (which is what I am using now), so I'd suggest starting there and find out what's in that Carb. You mention it's from a racecar, so I'm guessing they've been swapped out for something to provide more juice to the engine. I wish I was your guy, but there are some good videos out there that cover more of this stuff. I hope to make some videos someday that covers more of this stuff, I just haven't gotten to it yet. :)

Yes, I kept going back to look in the car at the tach while I was adjusting this. :)

Sorry Brotha, I wish I knew more about Carbs so I could tell you the performance difference. Hopefully as I get more seat time with this Hog, I'll be able to comment on the pros and cons. :)

Almost identical procedure. Adjusting the idle mixture screws is more or less the same on any carb, but their different location can throw people off. :)

@@AndyKruseChannel - i will send him this video, hopefully it helps him. thank you!

Maybe 100 RPMs, but not alot. It was enough that I wanted to wait until the fans turn off so I can get an accurate vacuum reading. :)

No problem. 🙂

Could be a couple things, possible vacuum leak or timing might be off. If you spray carb cleaner around the base of the carb and near ports and the RPMs climb, you've found a vacuum leak. If you have vacuum advance on the distributor and it was connected while the initial timing was being set, this may cause and issue too. It's really tough to diagnose some issues without being there. You may want to reach out on local groups and forums and see if someone can pop by and troubleshoot the issues you are having. :)

@@AndyKruseChannel I'll check that out, thxs sooo much. Cheers

I had a similar issue. Check or simply replace the "power valve." In my case, the "power valve" was stuck open which was dumping fuel at idle when it wasn't supposed to.

@@tstan6767 Thanks your awesome!!

My pleasure!

You're probably correct, but I haven't gotten that far yet. :)

I believe there are different length studs because there are different height air cleaners. I always run that stud 'til it bottoms out. I think I even cut one short for a previous build as it was hitting the hood. You also buy a piece of althread from the hardware store and make a custom length stud if you don't currently have one or you don't want to cut the one that came with your carb. :)

High idle in park is not bad, unless it's really high, then it's just not desirable. Adjusting your idle mixture screws with an Auto should be done with someone in the car, car in gear, and on the brake pedal while you adjust the idle mixture screws. For just plain idle adjustment, this is going to be a balancing game of where you want your idle in park and where you want it in gear, but they'll never be the same since there is a 'load' on the engine while in gear. :)

@@AndyKruseChannel ok so we did that and we adjusted it so the in gear idle is right then we get high park idle when I adjust the park idle to sit perfectly I put it in gear and it’s too low. That is why I currently only have a high idle In park. And it idles above 1100 for sure

@@AndyKruseChannel I will retry that in gear I did not read that part thank you

Sorry Boss, I haven't ordered anything from them. :)

No, they are independent systems. However, one could find they are changing both at the same time, depending on how they want to tune the Carb. :)

Thanks!

The choke plate? There are Carbs out there that don't have a Choke. They're typically not needed in warmer climates. :)

Thank you I appreciate your response

It's probably the fast idle adjustment needs to be reviewed. If your carb is like mine, it can be found on the back side of the electric choke mechanism next to the main carb housing and it will be adjusted with a small wrench (like 7/32 or something like that). Holley has a slick video on how to adjust that screw and they have a sneaky way to adjust it quickly without needing to adjust it, let the choke cool down, and then adjust again until you get it right. :)

@@AndyKruseChannel would it be clockwise or counter clockwise to bring it down?

@@FernandoHernandez-ri7rd Counterclockwise would lower the idle while the choke is engaged. :)

@@AndyKruseChannelGood call,Andy,the choke step ed up enough to stay running.cam has to synchronized properly with the throttle blade position(caused by the spring load in the choke housing).I’ve had to wrestle with these settings many times in the old days.Never liked sitting in the car till it stayed running in the winter.

Thanks for watching!

Thanks for the heads up.

Unfortunately Cams that seem to be anything other than stock will have this affect when trying to observe the vacuum. Not only does it bounce around, it will also be a lower value on the gauge, hence the comment I made about it not being about the specific number, but the highest number you can achieve. :)

@@AndyKruseChannel yep. My vacuum is about the same as yours.

find a liquid filled gauge..takes the bounce out.

I use motorcycle carb synch gauges with flow compensators to even out the vacuum. No bounce

Usually that means the valves are not adjusted properly letting exhaust gasses back into the intake tract. I have the same gauge and the needle is solid with my small block chevy.

If you have an automatic, yes. If you have a manual, no. :)

Thanks!

On my setup, I am trying to be around 800rpm at idle. Everyone has their preference. :)

No problem! 😀

Thank you too!

You and me both! :)

Nope, it's just right. :)

@@AndyKruseChannel please explain i did the math and came up different 347 X7000rpm=2429000 Divided by 3456 =702cfm and that hi rpm

@@scooter1391 Engine builder said to pair this carb with the engine he built me.

No, I use the manifold vacuum port on the carb to plug the vacuum gauge into during this adjustment. This is the same port that the vacuum advance on the distributor uses, so the vacuum advance is not connected during this adjustment. :)

It's a electric fan setup for a 1999 Ford Contour and it is a popular upgrade for people putting 347s in their Mustang. I have a video about the install on my Channel. :)

That's a complicated question. It depends on your engine build and your carb size. At the time I made this video, I was using the stock sized jets and they were number 72 jets. Since I made this video, I have tried 71, and 70 jets. But this goes with my carb size and build. On a car with a 302, this particular carb would be too big, so a smaller carb (like a 600CFM unit) would be a better fit. I don't know the stock jet size in those carbs, but you can pull them out and look. Finding the right size is an even more complicated question. :)

I talk about it in the beginning of the video when I'm explaining the two ports that the vacuum gauge can be connected to. I used the "Manifold Vacuum Port", which is on the front side of the Carb, below the front bowl. :)

Ok

Correct. 🙂

Timing is everything. :)

Louder than an EV. :)

@@AndyKruseChannel definitely have to agree! As I'm getting older, I don't mind a hotrod that's tamed a bit. Trying to break in cams or tune a carb with it louder then the gates of hell isn't logical to me anymore. Time and a place for those type of toys

No, engine can overheat.

@@AndyKruseChannel ahh, that makes sense. I'm an idiot LOL!

@@rorschach8167 Haha, no, but I miss obvious stuff all the time. Like that video I made about my wheel falling off. Now I need that emoji where my palm is slapping my forehead. 😆

@@AndyKruseChannel I need that emoji for pretty much life in general

Nope, I'm worse than that.

@@AndyKruseChannel lol! I had two cars with 780s, and there's a procedure and I've yet to see anyone do it properly ¿`_