How to adjust Holley Idle Mixture Screws and Curb Idle
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- Опубликовано: 1 фев 2023
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This video is about setting up and adjusting the Curb Idle and Idle Mixture Screws for Holley Carburetors.
Holley 4160 750cfm, vacuum secondaries, electric choke - Model no. 80508S - Amazon Link: amzn.to/3CU0Szr
The car is a 1966 Mustang Fastback with a 347 Stroker and T5 transmission.
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The accelerator-pump adjustment segment is excellent! Thank You!
Awesome, glad I can help! :)
Straight forward and easy to follow, will be using these steps and tips this weekend
Awesome! :)
First video that actually explained everything. Thank you so much. My truck is Running Better than Ever! 89' Chevy C1500 4.3l V6 - TBI to Carb Swap!!
Awesome, I’m glad I can help. 🙂
I've commented before but I'll comment again. This is by far the most helpful video I have found about adjusting a carburetor on RUclips. No bullshit, just helpful information explained in a very simple way. If you don't do this professionally, you should.
Thank you!! :)
@@AndyKruseChannel now if I could just figure out how to use my timing light.....🙄
@@rorschach8167 💡?😳
This is the best video I've seen explaining it. Great job
Thanks! :)
Coming along great Andy!
Thanks 👍
looking forward to your first drive with the new engine!
You and me both!
Good video. You made it simple enough, even I learned something.
Glad it helped
Great video Andy, I am going to give this a try, Thanks
You got this!!
Awesome video man 💪🏽💯
Thanks!
Thank you for sharing your experience
My pleasure!
Nice bro mine is almost ready to crank can wait to see the drive video
Coming soon. :)
Hi Andy! Nice and very detailed. As for the accelerator pump arm adjustment. .015 on the feeler gauge is where we want to be per Holley. I have seen guys that bury that arm into the diaphram like you eluded to. Thanks for sharing another gem with us. Good stuff.
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.
Thanks for the Vid, very helpful
No problem. 🙂
great and informative video!! Thank you
My pleasure!
Should also touch on how to set the float levels. A few times now I’ve had friends with Holleys go through tuning like you show and can never get it to be snappy. I found it easier and better to set float levels and then tune from there. Nice video! Short sweet and to the point!
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.
Great video!
Thanks!
Big help bud great vid, great people like you is why people like us have hat rods thanks bud.
No problem 👍
You must be a Baker because when you explained that, it was "A Piece Of Cake". I never knew this and I'm old school. Dad never had a vacuum gauge . He just went by feel and sound and engine response. Now I'm a Happy Camper. Subbed and Thumbed. Nice Engine you have there!!
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! :)
Nice video! Thanks
Thank you too!
Thanks for the info.
No problem! 😀
great job thanks
Thanks for watching!
Had three, complete,, early 60s tri-power setups, for FE big block Fords,,, always closed the outer carburetors idle screws,, and outer carburetor butterfly plates closed as much as possible without jamming,, did all idle mixture screw settings on center carb only,, actually was able to get 19 mi to gallon on the open highway,, these tri-power setups idled perfectly and needed very little maintenance... 0:16
Yeah, these are fun to work on. :)
Using a Holley street avenger 770 CFM. 1000 rpm park and 800 rpm drive looks like the sweet spot (400 - 425 hp 350 sbc). Anything lower causes either a stall shifting into drive or a slow one after 15 mins of driving.
Good to know.
I don't understand why people don't know to turn the mixture screws open 1/4 to 1/2 turn from highest vacuum or fastest idle. This allows a little extra rich which offsets a potential lean condition that occurs when the least little bit of contamination gets into the idle circuit. you can go a longer time before having to readjust the mixture screws. You barely change the idle at this richer setting and don't need to redo it until a LATER time. I have done this for 53 years. It should be common knowledge by now.
Yes, this is a good option. :)
Yeah cause they still make them that way lol
@@AndyKruseChannelukssssp❤😂😂😂😂😢🎉😢😅
Was looking forward to this part. When your fans kick in, how much load does it take on the engine and drop the rpms? I’m trying to find the sweet spot so it doesn’t stall out on me. Great video!
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. :)
Hey Andy, great video! Quick question, have you every ordered parts from Restoration Parts Source? I a few of us were talking about them over on Scott Harness’ channel and I wanted to see if you had any experience with them.
Sorry Boss, I haven't ordered anything from them. :)
A air fuel ratio gauge is the way to go saved me so much time
Yep. :)
Helpful video especially on where to hook up the vacuum gauge, thanks. Holley says if you move one mixture screw 1/2 turn, then they all have to be exactly the same.
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.
Hello i got a holley carb 4150, 715 cfm, its on marine engine volvo penta 5.7, and it doesnt have any ports for vacuum gauge, any advice how can i adjust the mixture screws? Thank you!
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. :)
This may be a noob question. I just bought a project 79 mustang that came with a Holley 600 street warrior with no electric or mechanical choke hooked up. Are you always supposed to start a carb with a choke - or can carb be tuned so you don’t need to use a choke to start if that makes sense?
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.
Two things I do before anything is make sure the fuel pressure and the float bowls are right. With out that everything else is moot.
Yep, good advice.
I have one question, I bought holley 750 put it on and it was running so rich it was smoking, now after watching your vid I was thinking maybe the excel pump needs to be adjusted it just seemed it was just dumping gas in whats your thought on that thank you bud?
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 RUclips for every scenario. :)
Whats up bro, any info on the screw inside the stud wher the air filter connects what is the normal adjustment for that like how many turns out or in
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. :)
I have a 65 fastback as well. Do you possibly have roller rockers? At idle, it kinda sounded like a sewing machine and mine has always sounded like that after it warmed up. Super annoying to be honest, but I’ve always been told it’s normal.
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. :)
Thanks for this, does your car have a tach? Assume that’s what you are judging RPM’s for curb idle screw?
Yes, I kept going back to look in the car at the tach while I was adjusting this. :)
Surprised how smooth it idles with that aggressive cam.
You and me both! :)
Having a bit of a problem. Would this kind of tuning help with this? I have 750 double pumper Holley. A friend of mine rebuilt it for us, told us he tuned to throw in a lot of gas since it’s a race car. It is a ford small block, and the idle is way high at 2300-2400 RPM. Would this kind of tuning help or is it something deeper? I’m brand new to carbs and this all a foreign language to me😂.
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. :)
You mention capping off Ported Port. Would that also mean to fully disconnect Vacuum Advance and just cap the Port at the carb?
Yes
I have the same fuel rail from Earls. On the second one and can't stop the leaks.
That just means you're making too much power! :)
when you changing the power valve do you have to change the jets at the same time
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. :)
It is very interesting, you are talking about fine adjustment on idle mixture screws and reading vacuum gauge, but there is absolutely no changes on gauge at all while you are turning screws 😅 Great in theory, but in practice I didn't see that you fine tuned anything...
Cool, glad I could help you. :)
My carb is setup way rich, so I'm assuming that turning the Mixture Screw to the right is richer and to the left is leaner. Is this correct?
Backing the screw out away from the Carb is adding fuel, equaling a richer condition.
When the accelerator pump is not adjusted correctly, it will not feed fuel (contrary to the claim in this video) unless you move the accelerator pedal. The way to adjust it is to make sure you get the full travel of the link so you have access to all the fuel volume available inside the pump. You also want it to react promptly so to much free play is not good for a solid & fast engine response.
Ok
Quick question for you if you have any advice. My four barrel Holley on cold start revs really high eventually coming down but is practically screaming while warming up. And if I feather the gas pedal it sometimes comes back down but sometimes just sticks. Any ideas?
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.
I’ll be interest if you noticed much difference between the Holley and Edelbrock carb
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. :)
My vacuum gauge needle bounces around just like yours on my 347 making it a bit of a challenge to set the idle mixture. I've seen other videos where the needle was rock steady and was worried I had another problem so I was relieved to see yours.
I'm guessing the bigger cam has something to do with it.
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.
So I need to disconnect the vacuum advance and plug it off on the carb to adjust it with the vacuum gauge?
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. :)
What fuel pressure are you running? It looked like it was between 2 and 3 psi.
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 👍🏻
What is the name of the flap that sit on the top of the carb, for some reason I am missing that piece and trying purchase it
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
my friend has a Holley hr-650 hot rod series carb. What are the chances the carb settings would be the same for his carb, that you have in this video? Sorry, I know nothing about these carbs. he asked me for help, but i know nothing. (i only know Solex 30pict carbs :) )
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!
Do you have to put the car in gear or under load to do this?
If you have an automatic, yes. If you have a manual, no. :)
Do you do this with vacuum advance hooked up?
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. :)
Just fyi,, not having a secondary metering plate has nothing to do with rather or not your carb has vacuum secondary’s, my vacuum secondary holley has 4 corner idle adjustment screws
Thanks for the heads up.
I just bought a 1968 mustang fastback with a 302 in it I’m 19 years old and I don’t know a whole lot about carbs I just wanna make sure I’m not running too rich I did the typical 1/4 turn my engine idols fine after it’s warm but I just wanna be sure I’ve done it right can anyone of you guys help ?
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 RUclips video is not really the best place to have a discussion about how to tune your Carb. :)
The gauges are bouncing around so much, how can you determine the optimum setting?
It's not about an optimum setting, just the highest value you can read.
Hey what fan are you using???
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. :)
A bigger cam that causes a vacuum of about 9 inches may require a power valve replacement.
You're probably correct, but I haven't gotten that far yet. :)
Could you show where you attached the gauge?
It goes on the port located below the front bowl. This is the manifold vacuum port. :)
great vid-- i have a holley 4 barrel vacumn secondarys wont idle below 1200 rpm and back fires above 1500 rpm --mixture screws turned all the way in has no effect on rpm, carb was cleaned--any help apreciated will pay anybody that can help
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!!
Que jets usas en tu 302m
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 need help high idle in park and when I put into gear and hold the brake the idle is perfect
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
The reason you don't have a metering block in the back of that carburetors cuz Holly is gone cheap the older vacuum secondary carbs had met during blocks in the back with a four-corner idle.
Thanks for the heads up.
7:07 What RPM are you looking for at idle?
On my setup, I am trying to be around 800rpm at idle. Everyone has their preference. :)
Your method of setting the initial curb idle screw adjustment is incorrect because it does not take into account the idle transition slot.. This needs to be set before installing the carb. The proper way is to turn the carb upside down and adjust the curb idle screw so that the idle transition slot appears as a small square. Then install the carb and and see where the engine idles. If idle is too slow increase the adjustment until you reach the desired RPM, noting how far in you have to turn the screw. If you have to go in more than about half a turn you are exposing too much of the idle transition slot. In that case curb idle speed should be raised by increasing initial timing. Oftentimes just switching from ported to direct manifold vacuum advance will do the trick. If it is necessary to increase idle speed with more initial mechanical advance this should be compensated for by adjusting the timing curve in the distributor.
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 :)
is't that carb a little to big for that motor? are you spinning it over 7k,
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.
You don't show where you plug in the vacuum guage.
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. :)
Looks like clockwise is Leaner and counter clockwise is Richer.
Correct. 🙂
Just after I buy Holley efi kit …
Timing is everything. :)
If the accelerator pump is adjusted too far. As in touching the linkage a bit, it will not simply dump fuel in the carb. The way the diaphram works is by movement. Not saying you shouldnt get it as close to touching without it actually touching, but your info is wrong
Ok
He said the engine is loud. 😅
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
Wouldn't it have been easier just to unplug your electric fan? Not being a smart-ass, just wondering.
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
Typical backyard mechanic oh, but he's got a gauge ¿`_
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 ¿`_