Holley Carburetor Jetting Tuning Guide And Explanation | Holley Carb Secrets |
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- Опубліковано 13 лют 2021
- Lengthy video on tuning the jets on your holley carb. this info can translate to any holley 4150 and 4160 style carbs. Too many people have no idea how jetting even works so this video is to enlighten those people and prevent them from spouting nonsense and giving people bad advice. Once you get the basics of how jetting works in a holley carburetor, the rest is easy as long as you tune in the triangle formula.
#holley #holleycarbs #carbedls
Holley Carburetor Jetting Tuning Guide And Explanation | Holley Carb Secrets |
There's been a raging debate on this topic for as long as I can remember. On one side you have the purists that want everything period correct and on the other you have the hot rodders who will even mill off the choke horns for more CFM. People often ask how to adjust choke on holley carb or holley carb choke removal because they seem to be dealing with a problem that is related to the choke cold start system as a whole. Hopefully this holley carburetor video finds you well and you enjoy this little opinion piece.
Holley Carb Choke Problems And Removal | Holley Carburetor Secrets |
I'm sure most of you have had a flooding issue or a carb running rich and you just don't realize whats going on and even if you do happen to figure out what is happening, sometimes you don't even know what to look for. Holley carbs are some of the most versatile car parts but even they have their own set of issues. holley carburetors depend on a well balanced fuel level in order for them to work correctly. Once the balance is tipped to one side or the other, you can have several problems such and fuel coming out the vent tube, have the holley carb secondaries flood, holley carb running rich, holley carb hard start and even fuel leaks and dripping from boosters. So come by, sit back, relax, and enjoy the show to learn a little bit more about holley carb tuning!
Finally getting around to making this video, everyone loves the HP main bodies because they look super racecar with the adjustable air bleeds on top. What if I was to tell you that you can install custom air bleeds on any holley carb as long as its a squarebore? There is just enough meat on the top of these older holley carbs to allow you to install the adjustable bleeds, but you would be very careful when doing so because you can ruin your main body real quick!
After A long while I have put the most cohesive method of setting up the idle on your holley carb. Setting the idle mixture screws and getting your engine to run clean without having to buy any special tools. In this video I manage to set up the idle in less than 15 mins and also do it quickly and easily. As of right now, the holley carb on the 318 duster is perfectly set up in both idle mixture and idle speed. The carburetor in question is a DEMON 625, an older barry grant holley copy before holley bought out DEMON. It took a little bit of work, but I've got this set up perfectly.
Tuning Holley carbs are probably the most widely used carb is all of automotive history. The Holley 4 barrel is a staple among racers and cruiser a like but too few people really understand what goes on inside their Holley carb and too many decide to ditch the old carb in favor of a new one. I am here to share 5 secrets you can employ TODAY to get that Holley nice and tuned and running better than ever in true DIY fashion. I'm put to work these 5 secretes to get my Carb ls going so these are definitely something you need to keep in mind. Tuning a holley carb is what separates the boys from the racers. Depending on how well this video does, I'll be breaking up and going into full detail of what goes on specifically in the different circuits as well so stay tuned!
How to set idle on a holley and other such questions are answered!Holley carb wont idle? Car wont idle? Holley carb runs rich? Holley carb wont start hot?all these questions AND MORE will be answered TODAY. too many people have no idea how the holley idle and transition circuit work on a holley carb.too many people belong to the set it and forget it line of thinking when it comes to out of the box carbs and not too many really know whats going on and decide to just give the carb a bad rap.Well, today we are going into an in depth tutorial and explaining on how these systems work and how you can get more out of your carburetor, maybe even pull up a few MPGs while you are at it! - Авто та транспорт
Kind of a longer video. It used to be an hour and a half and I trimmed the most that I could I promise!
I converted a vac secondary 600cfm that had a secondary squirter boss into a true double pumper. Even machined the baseplate for a secondary pump arm and spring pearch. This was a rare opportunity to actually see jetting difference. From being a vac secondary to true double pumper. Jets were identical. 65/65. Front and rear. 28 squirter primary. 31 secondary. Pink pump cams. 351w roller motor. Carb rips. Perfect on wideband. Also had converted it to 4 corner idle. Ps. U can use wire on baseplate to block off front to back transfers slot for 4 corner idle. Or just use epoxy
Absolutely LOVE these videos on the holleys great work!
Thanks man! I really appreciate it!
Good job ! Helped me understand some fine points that I never knew before.
Thanks man! I'm glad it helped!
Another great tuning video thanks for teaching
No problem man, Thanks 👍
We should dig up old Holley 950 three barrel and run it on test engine
@@jamesrobinson9062 I've seen them, but they dont flow nearly as good as a similar sized 4 barrel
Absolutely THE best carb jetting info ever!!!!
SUBSCRIBED!!!!
I wish you had a way to reach you - for recommendations on what I need on my 496 stroker for my jet boat. I have a Weiand tunnel ram and two Brawler 750 double pumpers mounted side saddle….. the primary jets are 74, secondary’s 84 with a 4.5 power valve. I have 10.5:1 compression and my cam is a pretty big Howard’s .640/ .640 lift, 296/ 308 (243/ 255 @ .50) and a 114 centerline. It’s a hydraulic roller retro-fit. I’m most concerned with the carb jetting, so I don’t melt a valve or piston break nag too lean…… other friends have said, I need to be “square “ on my jets for both carbs, but I have no idea where to start! My carbs are brand new out of the box from Holley like I stated, and it starts and idles good- so far.
Can you please help a brother out!!
Hey man, i would advise that you install a wide band and lear how to read it because it could sace your engine. Square jetting is for drag racing where you run WOT the whole way. If you run a PV, theres no way to run square jets. The PV compensates for the missing jets on the primaries at WOT. Id say run it as is slowly, and if you feel hesitation, jet up 4 sizes on whatever circuit you are on.
Hello. Love your stuff. I have a 68 bronco with a holley carb that is leaking on the left side there is a brass cirxle that is on the left it is on the top side of the carb. There is a tube on that side on the top horizontally and where the rube foes into the carb there is a brass circle about a size of a centimeter and a half. When you push on the brass circle you can feel it give way and it is not seating well so fuel is leaking out there. If you push on the brass circle more gas comes out and you can tell it is not tight or seating. Not sure how to get it tight or dixed. 6:57 7:01 7:02
Damn.. that was a lot bro. lol..
Looks like I'll be sorting through your archives. We have a 383 stroker with 750 double pump, and it's fouling plugs. I was told someone swapped the primary and secondary jets- not sure why; But I'm going to start by reading them to see what we have/ swapping them back to the smaller jet on the secondary and start from there. It seems to run pretty well on the top end, but it's definitely flooding gas while idling, or on the lower end. Another problem is it sat for 10 years and has horrible gas; I'll go search out your videos on getting the idle jets and accelerator pump setup first. cheers.
Stupid question here; are both jets supposed to work at the same time? For a 2 bbl? Or is one a idle jet and the other a main jet.
On a 2 bbl holley, both jets work at the same time as main jets. The off idle or transition "jets" are built into the main body
Great video 👍🇦🇺
Thank you sir 👍
Thanks!!
Anytime 👍
Square jets... depends on secondary linkage. If primary/secondary movement is synced, that's probably achievable. If they are progressive [30, 50% or whatever] then you tend to go away from square. The application [outside of WOT drag racing] is almost irrelevant. The question is if the secondary opens later, what happens to plenum vacuum? If it drops enough, your primaries are asked to play in two worlds, even with increased air demand. So if say... a 76 might work both sides with synced movement, you could wind up something like 72/ 80 where secondaries don't pickup until primaries are open 50%. That, and secondaries having no power valve tilts away from square to begin with the moment part throttle driving is a required mode of operation.
Great video thanks for sharing! I am currently rebuilding my carb and was wondering if you could help in choosing the right jet and power valve size. The motor is a 440 with a mild comp cams (dont know the specs of the cam). Has edelbrock aluminum heads, headers, 750 double pump 4150 style holley with a stock style fuel pump. Its running rich from what I can tell. black smoke especially at cold start., Spark plugs are covered black all around. Once the engine warms up it runs pretty good and the black smoke clears. The carb has a 6.5 power valve and 72 jets in front and 80 in rear. I read the vacuum at idle to be around 8-9. Please let me know, I literally just took the carb apart and am going to put it back together in a few days after cleaning and replacing all parts. THANKS!
I think the jets are close to what you need. If anything, you'll want to dial in your idle mixture after recurving the distributor. I base jetting on horsepower so when I did a 400hp 383 sbc, it wanted 71f 76r. Im assuming your 440 will make a little more power so jetting should be close. Get your timing at idle around 15 degrees and have it max out around 30 or 32. After that work on carb tuning. Chances are youve got too much fuel at the transition
@@NightWrencher thank you so much for the response. I’m some what of a noob when it comes to carbs. I will look into it further in the coming days. Could I email you ?
Yeah thats no problem. I believe my email is listed here on youtube on my account
I've got a 289 ford that I'm going to throw an aluminum intake on and a choke style 600 quick fuel vs, I've considered the idea of buying an afr gauge and a o2 sensor to help with ease of tuning. i currently have a stock cam but am going to put in a milder cam to aid the intake and the carb. the 600 quick fuel has 68 primaries and 74 secondaries. should I jet down my secondaries as it's just going to be a streetcar? I'm more worried about leaning out my car than anything, I currently have a 2 barrel that I had trouble with it flooding the engine at cruising speeds and I finally got it dialed in a while back, the response off full throttle pulls good without hesitation, I'm just afraid of the consequences of trying to tune in the 600, I'm just used to the idle mixture screws and the throttle position and the float position. I'm just tired of breaking down on the side of the highway.
A 4 barrel anything will out perform any 2 barrel in low end torque and top end hp and get better mpg. Maybe I'll make a video on it. As for your jetting question, theres really no way to tell where the jets want to be unless you've done a similar combo before. For example, I've tuned a 383 sbc 670 and it wanted 71/74 jets. Ive tuned my stock 5.3 ls and it wanted 67/62. Added a 2" spacer and it went 69/64. Swapped to long tube headers and it went 70/65. Im sure after I install my cam its going to want something like 71/72 which is really close to what the 383 was at but 1 liter smaller. Id say, if you want to really dial in your carb to get a good balance of MPG and solid power, get a wide band. It could save your motor and will pay for itself in mpg
I have a 40 over sbc 485 485 L 298 duration solid lifter cam 125 dome 9.6.1 compression , air gap dp intake 75000 v super coil 45 thou plug gap timing set accordingly I found 14°adv is the sweet .. 4inch tall by 14 inch air cleaner with filter in the lid 750 holley VS 78 main jet running 13 on the air fuel guage ... I have a miss at wide open primary just before the vac secondary opens not bad but its annoying whats your thoughts ?
I would look at a richer main jet, leaner transition and maybe have the secondaries kick in sooner so you don't run out of main jet with rpm.
I have a 242 I6 4.0 running a holley 4412 carb... It runs good, even as I know is a big carb for the application... what jets should I use in order to get better milage same or better perfornce.. I know there is a smaller 350 cfm version but just looking to leanr and tune waht I have.. thanks..
Every engine and every carburetor is different so I would start by checking your spark plugs. If they're a light brown, I would leave it alone but if they're black, I would drop the jets down 4 sizes and see how it drives
Great video. I’m trying to tune my idle and more importantly my transition circuit. My idle afr is about 13.8 but my off idle cruising about 55 - 60 mph is 11.8 my plugs are black. Do I try and increase my air bleeders or do I decrease my idle fuel restrictors? I have an 830 cfm quick fuel on top of stroked 383 Mopar putting out 530hp. My vacuum at idle is 7 cruising 10. My transition slots are squared at idle, but my idle screws are only half to 3/4 turns out to get to idle at 800 rpm. I have a 4 speed car
Thx
Hey man, Theres a lot to unpack here. The main issue is the rich transition. Your tranfer slot wont have anything to do with that since you're at a consistant rpm. Are you sure that youre looking at the transition and not the main circuit? Some people don't know how to tell the difference even with an AFR gauge. I wouldnt increase the size of the air bleeds because it will slow down the response of the fuel that comes in and might cause lean spikes. If you're sure the issue is in the transition circuit, I would drop down .002 or .004 on the IFRs. You should be close since youre about half a turn out on the idle. Theres a big difference in tuning a manual vs an auto car since its easier to lug the engine at cruising speeds but that would cause a lean condition so we can rule out gearing.
NightWrencher
Thanks for the reply
I’m cruising about 65mph tacking about 2800rpm steady speed for miles and I’m barely touching the gas pedal which makes me believe the primary throttle blades are still on the transfer slots and not fully on main jets. I did go down 3 sizes on main jets and it made a small difference on plug color. I going to try like u said and reduce my IFR .004 and c how that works before I further reduce main jets
Thanks Again
@@hilide let me know how it turns out!
@@hilide how did it turn out?
@@jakefriesenjake
Hi Jake
I ended up going one step hotter on the spark plugs.I also replaced the idle fuel restrictors two sizes smaller
I also replaced my primary main jets from 76 to 70
My AFR is now 13.5 at cruising speed
The power output of an engine is directly proportional to the breathing capabilities of the engine. In other words, how much and how easy can an engine get air in and out through the combustion chamber...
For years the rule of thumb for carburetor size was, you can safely use 2X engine displacement to sect the size of your carburetor. As an example we can say that Ford 289/302 cid engines will perform well with 600/650 cfm carburetors. For serious racing you can go 3X engine displacement without any problems. During the 1960's and '70, I raced big block Ford engines with two 600 cfm carburetors. Keep in mind, engine make up, timing and fuel system must be tuned accordingly.
Cheers!
Great content I subscribed after watching a few of your carb vids. What size carb would you suggest as a starting point for my 600hp 454? It's a mild build revs to 6k with 3.73s out back th400 3k stall, Purely a street toy thanks alot
Thank you! I would probably go with a 750 or 780 vacuum secondary carb. Streetability is really nice with a VS especially if you dont have a wideband to fine tune the secondaries
@@NightWrencher thanks for the suggestion. Orginally had a 1050 dominator on the car and felt it was too much (barely would need to open the secondaries) so at the moment I have a 750 VS on it. Runs great and my throttle response is instant, might step up to an 850 mechanical secondary as the dominator felt better on the top end.
If you're going to step it up go with the 830hp. Essentially 750 main body with 850 baseplate but with 4 corner downleg boosters and radius entry venturies and no choke
You still shouldnt need that much carb but I would dyno test them back to back to see if the gains are worth the price
@@NightWrencher yeah everyone says cant go wrong with the 950hp (flows 830).... maybe I'll keep saving for one. thanks again
I have a 4160 carburetor of 600 cfm in an original Ford 302 engine without modifications from 75, the idle fails, no carburetor, the mixture screws inactive They are completely closed because if I open them the engine starts to fail, say The jets are big, could that be the reason?
So, start with idle circuit, then transfer circuit, primary jets, pv, then secondary jets?
Yeah pretty much exactly in the order except after you adjust the IFRs youll have to go back and redo the idle but its not too bad
My 1850 doesn’t have a metering plate on the rear of the carb. I can’t seem to wrap my head around the little aluminum plate and secondary jets if I don’t have a full metering plate. Just float and what looks like a block off plate.
Its either got a metering plate or a metering block. The plate just looks like a flat cover with little holes on the bottom that regulates the jetting
So if I have a idle AFR of 12.5 but when I push the gas it starts going Leann to about 21.5 is that the transition restrictor I would need to change to get the the AFR to 12.5 when pushing the gas.the topend goes rich to 9.5 at about 3/4 pedal.
It depends where exactly youre holding the throttle. If youre holding it steady at light throttle and it goes lean, that would be your IFR. If youre accelerating past light throttle into more throttle then it could be another circuit
Soon as u push the pedal. ill have to just keep trying .
I’m having a flat spot problem ,
89 351w stock , edelbrock performer intake , shorty headers , vacuum advance dizzy initial timing 14°, total timing is around 35°, Holley 4160 1850 carb , fresh rebuild good fuel pressure , floats set , vacuum secondarys are opening checked with a paper clip ( running the brown spring ) , truck is a 87 bronco , 5.88gears , c6 trans on 37” tires , I’m running lean for sure but not terribly . Pulls hard till 3,100-3,200rpm then flat lines like a lean bog maybe . First experience with a Holley so I’m not sure if maybe the secondary’s aren’t opening enough ? Or is there a way to jet up the secondaries or do I need to jet up the mains ? Just a lil stumped
@nightwrencher ?
Im going to go out on a limb and say its actually flooding when the secondaries kick in. Lean bog would hesitate, shake and probably pop out of the carb. The 1850s use a metering plate instead of jets to meter fuel so turning them down gets a little difficult. Find some really thin wire like .020 or .025 and try to stick it into the bottom holes of the metering plate where it pulls fuel and that should lean it out some. How much exactly I dont know but if it gets better, you'll have your answer. Loosen the plate, stick the wires in the 2 metering holes at the bottom of the plate and fold it back so that when you tighten the plate back it will sandwhich the wires. Fold back the wire as short as you can so it doesnt interfere with the gasket sealing surface.
@@NightWrencher it does shake and backfire when it flat lines , almost as if it feels like it’s running out of gas . I have the parts in cart and thinking about just putting the 4150 conversion kit on it and jetting, atleast that way there’s no guess work, maybe if that’s the right way of thinking
hey man, youtube hid your latest comment so I just saw it. the popping out the carb is the #1 sign of it running lean. On an 1850 you can drill out the secondary metering plate if its too small but you need to verify the size it is now, and compare it to what it should be. you can do the 4150 conversion but it might not fix the issue. If you plan to drive the truck a lot, it might be worth getting a wide band.
I’m having some trouble with my brawler 650 on my mild sbc vortec heads mild cam dual plane (my engine build) it seems to run crazy rich puffs black and fouls plugs anyone have a similar issue?
What does your wideband say? If you have a wideband you can pinpoint exactly what circuit youre on and tune it.
Building a sbf 427.
Going to make high 500 to low 600hp. I will be using pump gas e85 fuel.
Looking at buying a 750 e85 version. ( the expensive one )
The guy building my motor suggested the 750. Because of the drivability. Because Holleys calculator comes up with the 950. As the suggested size.
My car is a 67 mustang.
5spd with 389 gears.
Right about 3000lbs total weight.
Car is an autocross, street & some gear jammer bracket racing use.
I was going to suggest the 950xp which an 830cfm until you said autocross. Theres a lot of snap throttle in autocross courses and I think it would drive better with the 750
Hi there do know what number jet stock 600 cfm
I depends on the model. Not all 600s are jetted the same. Somewhere in the 65/66 to 70/72 range is usually where they sit. You can look up the list number and find those details online
23:10 .... not always, in my case, i currently have a holley 3310-2, 3310-16, 770SA and used to own a 650vs classic, the IFR on the 650vs classic was a massive .039 versus the 3310/770SA which are at .033 . I'd probably expect the .039 IFR on a 650DP because they tend to run richer than their vacuum secondary counterpart, but i've never owned one, so im not sure. So maybe the metering block got mixed up by mistake, also comparing that .039 IFR with a 670SA, that IFR is .028 in size for the retail boxed version, the crate engine version 670SA uses .026 IFR, of which i currently own as well, the crate version.
What carberator do you recommend for a stroked 6.0 so 408 and I wanna run nitrous
I'd say a 750 or 780 would give you good performance down low and pleanty of power up top. The nitrous plate should be a wet system so it wouldn't matter how big the carb is because the nitrous would add both air and fuel. Vacuum secondary of street car, mechanical secondary if race car.
Awesome thx for the great help/advice and keep up the work bud
@@adriandelatorre9526 thanks man, I appreciate it!
Also one more question, what if it just a full bolt on 6.0 which carberator should we go with?
@@adriandelatorre9526 Its really application specific but the go to carbs sizes are the 650 and 670. Both should get you to at least 350whp. Theres different versions of those carbs so pick the one that has the closest jetting out of the box for your engine. Something close to 70/70 for jets
I'm up against a wall.
I had a 600cmf holley but the back does not have jets.The 351w ran ok at idle but seem to run out at high rpm.Did have a slight hesitation when you first acceleration.Had 66 jets in the front.
I picked up a 750 quick fuel carb with vacuum secondary for cheap.I put 68 in the front and 76 in the back.Came with 72 front 82 back.Runs to rich have fouled plugs.I have installed a air fuel gauge and am running to rich at idle 10.4 - 10.6. Rich cruising 11.5 - 12.4. Not real bad under load on a hill 11.1- 12.1.Run I smash the throttle after that it goes down to 9.5 for a split second then up to 12.5-13.4.
These numbers are after I down sized the jets in the front to 66 the same as the 600.
My next move is the back jets down to ?? 70 maybe . I have a 4.5 power valve have vacuum pressure at 9.5 .The 750 runs better than the 600 hands down.
It's a 87 f150 dual plane gt40 heads I have completely rebuilt motor top to bottom .The best quarter mile was 15.3 but fouled the plugs the second time I went back to the strip.Any advice on the jet sizes would be appreciated thanks for the video really good information.
Hey man, for some reason I am barely getting the notification of your coment. It sounds like your carb is way out of whack. You need to remember that holleys tune like a pyramid, as in each circuit builds into the next one. Where I would start would be and setting your idle at around 750rpms and highest vacuum at idle, that way you make sure the t slot is almost closed. The following step would be to drive at very light throttle, that way you can see what the transition is doing. Willing to bet the transition is too big. After you fix those 2 items, recheck your main jet afr and if its still rich in the primaries, jet down. You have a pretty wild cam so your AFR is going to lie to you a bit due to the overlap so you want to aim in the low 13s high 12s for almost all the circuits except WOT
@@NightWrencher Thanks for your reply.I bought a metering block for the back of the holley 600cfm.Now I can jet up or down on the secondary.I think the 750 is to big and harder to dial in.Plus the air speed will be higher on the 600.Better atomized fuel in theory.The kit had a chart to go by to determine where you are at for jetting.Mine was stamped 39 which equals 70 jet size. So I'm starting with 72 because of the lean out at full throttle.The afr gauge should make this a lot easier than before.
Like your video was saying might have to go bigger in the front smaller in the back.
The cam still uses a stock converter really just a good towing cam with lots of torque from 1500rpm out to 4000rpm with my dual plane intake.My truck weight is 4000 with me in it with the traction bars the truck launches off well with the drag tires.The 3.90 gear really gets the rpm up quickly with my c6 tranny.
I will take your advice and do the tune all over again like you said to do thanks love your insight with your video's keep up the good work..
Good luck! As long as you tune from bottom(idle/Transition) to top(Secondary jets/secondary PV) you should be able to get it dialed in no matter the size of the carb
I have a 383 stroker motor. I Just put a new holly carburetor do i need bigger Jets for that size motor. Because my headers are glowing red and the truck don’t feel smooth ?
Depends on a lot of factors. Here are the specs that we used for a SBC 383, mild cam, 670 Holley
70 Primary
72 Secondary
.032 IFR
6.5 PV
50cc accel pump with brown cam
Do you think the Jets will be an issue?
@@NightWrencher my motor is a zz383 so you think the ones that it comes with stock won’t work?
Its hard to tell because I dont know whats inside. Did the carb come with the engine?
@@NightWrencher no I bought it from my local store.
I have a 650 speed demon on my built 383 Chev stroker. Made 511hp and 492 tq on an engine dyno.
74 on primary and 83 in the sec.
Very nice man, stout engine for sure
@@NightWrencher I'm tuning it for the streets now. I pulled the prime jets down from 74 to 70.. Probably will try 68 or 66. The pvcr is at 0.059".
I already drilled and tapped the ifr from around 0.032" or so to 0.026", went a little too lean down low so will drill the Brass set screws to 0.028".
At 3000 cruise, I'm pulling 15", and installed a 4.5" pv. Getting close!
Then I will tune the secondaries!
Thanks for the vids!
What I like to do is take my cruise and start to accelerate slightly up a hill and see how low the vacuum will go. Then, I install the PV to that vacuum reading and lean out the main jets
@@NightWrencher I did that... I cruise at 15", and I tryed a 8.5". It did work, but it probably activated too early, especially for hardly any load for the engine. The problem was that when I took off from a stop light (4.5" - 5" Vac at idle), if I gave it too much gas, the valve would open-up at below 8.5" Vac and above around 1800 rpms when the boosters start to flow, dumping fuel. It would ping 10 afr. At 2000 rpm...... Swapped it to a 3.5", it was good, then I put in a 4.5", still good.
If I get on the gas, in a split second, it's at 1" Vac, no problem. No excessive rich or lean spikes.
My only problem is now it pings lean at touch if I slowly give it gas, but not if I get on it good.
I closed up my ifr to 0.026", and that's probably a tad much. Going to open it up to 0.028".
We'll see what happens!
Very nice, it looks like you got it handled, great job!
A/F gage is worth it's weight in gold when jetting a carb
exactly right!
Articulate & knowledgeable
Much appreciated 👍
Your kinda close. When your tuning anything carb or efi the only thing your actually adjusting for is changes in air speed and density. You or your carb have no idea how much air there is in cfm . flow has zero to do with tuning. air density and air speed is what we are adjusting to . Slower air speeds mean a lower percentage of atomized fuel is actually making it into the chamber there for you jet up.
What did he say?
Carbs rule
I knew all that....................................
No no no