I bought a car with a Holley 750/mechanical secondaries and your video really helped me get her running just right now. The carb was WAYYYY out. Thanks for the info. Nice and clear video

That was some good info on the idle set. You've got that Galaxie sounding really nice. Being a Ford man myself, I like to see and hear something besides what brand X has to offer. On the size of the Allen head screw, (actually called a "set screw"), it's a thread size #10-32 X 3/8" long. Any good hardware store should have them. If you have a problem accessing the screw from the bottom side once the carb is mounted, you can flip the screw around so that the head is on the top side. You'll need to shut the engine down and place the carb at open throttle and move the secondary arm to get the Allen wrench in place to make an adjustment, but it will be easier than having to remove the carb, that's for sure. One more thing that I've discovered on these Holley carbs is that sometimes this screw will have a sloppy fit. To fix this loose fit, you can wrap some Teflon thread sealing tape around the screw to take up the slack and keep the screw in place. I wouldn't use Lock-Tite because sometimes it works too well and you'll strip the Allen head portion of the screw when you try to make an adjustment.

Very informative! Thanks, I just grabbed a used Holley and have been wanting to properly set the idle. This gives me a great place to start and adjust timing from there.

Great video man, good info. I just switched from Edelbrock to Holley and still learning all the different stuff you can adjust.

I wish I had seen this 6 years ago! Great tip using the secondary to set idle. Never too late to learn something new!

Very good advise, optimum transfer slot exposure is .045, which results in the opening being open the same amount as the width, aka “Square” Setting the curb idle with the Secondary throttle blade works great unless you have a really low manifold vacuum. Plus there’s other concerns when your dealing with a 4 corner idle carb in terms of balancing the carb, that’s when you can play with adding small holes in the throttle blades and/or use the Barry Grant idle ease feature. Both ways adding holes/idle ease were implemented to add idle air while maintaining the transfer slot function. Great Video! 👍👍👍

Your tutorial really helped me adjust my 670 holley. Thanks

Great suggestion on the allen key and allen screw. I have a 90 degree, low-profile screw driver set that I use to adjust this secondary throttle screw.

This some of the best advice I've heard. I have a '83 F-250 w/ a 460 and Holley 4160 750 CFM, #73 primary jets and a #25 secondary metering plate @ 6,000 feet elevation. I could either get my carb to idle right and bog at part throttle or idle rich and run great but not both. I had never thought to use the secondaries for idle. Set the choke up, turned the idle screws out 1 1/2 turns from full seat, and left the transfer slots were he said. After it warmed up, my 460 was idling at about 1100 RPM so I turned the curb idle screw out 3/4 turn and now it idles at the proper 650-700 RPM. Pulls like no other and does 40-70 MPH pulls in fourth gear in about four seconds. Thanks, Thunderhead289!

I got a new 600 cfm Holley vac sec (1850) and put a metric M5x20 screw with hex head in it and used a nut to fix the adjustment. Works great.

I used a 1 1/2" long screw an put a light film of silicone so it will stay where I left it for vibration control,i adjust it while it's running,works excellent!

You answered alot of questions for me thanks!

I've thought about setting mine up like this. Just swapped my freshly built 327 with a 383 (i couldn't keep up 💨). I built it from scratch, 800 main body, billet aluminum hi flow metering blocks, base plate is tight with all new brass floats and everything. Worked awesome on my 327 then put it on my cj7 jeep 304 for a month then in on the stroker but i swapped the jets from 68 f 74 r to 73 f and 78 rear. Hasn't been right since, I've jetted down, checked for all sorts of possible air leak areas, swapped the power valve but nothing. It'll only idle at a very hi rmp but not in gear unless idled extremely high and if you try to idle it down It'll just die. The more you screw the idle air screws out the higher it idles but no matter what i try it i can't get it back to normal. Going to try your setup this weekend and see how it goes. Motor is .060 bore, scat 9000 3.75 crank/5.7 rod, flycut huge dome pistons, 1969 041X heads shaved to 62cc and running an elgin solid lift 30/30 duntov cam and lifters. Strange that the carb worked flawlessly on my 10.25:1 40 over 327 tight lash isky .465 solid grind and the jeep 304 with a small elgin .465 hyd. I had a 750 vacuum secondary on the 383 the 1st week i ran it and that carb worked good on it but jetted down and on the cj now. Do you think maybe it's throttle plate related, run 2 fuel filters and only run 110 octane turbo blue racing fuel at 12.5:1 compression

Awesome video about mechanical secondary and timing 👏

Great tip on keeping your high signal strength on your idle circuit with a big cam with really too much over lap, another top would be to incorporate a air bleed off in the center port which I believe Holley has already done.

First accurate video iv watched, excellent

Good idea with the Allen screw for secondary adjustment. The way I went with that was just flip the secondaries adjustment screw over when carb is off motor so the flat slot is pointing up. It can then be accessible without hassle. Great video btw a lot of good pointers.

A lot of the racers with double pumpers adjust their transfer slots square, then they start out with a smalll drill and drill a hole in each primary butterfly, and possibly step up the drill size.

I took my Carter AFB off my 64 Buick Riviera to check this stuff. The primaries were not even close to square! I readjusted the floats and mounted it up and it works again!! Only thing is the high idle cam does not engage the idle screw and the choke isn't effective. Longer screw? BUT VERY COOL INFOMATION. Keep it up.

How much should the secondary blade be opened or is it variable based on the engine cam? Thanks

I've recently started learning about these and how to really set up a holley, as I've always used a summit or edelbrock which seem to be fine already when I get them. I have an almost stock 390 FE with an "RV" cam that just has a little more lift/duration than stock. I have a summit distributor and where it's curved right now I need like 15° BTDC initial timing to get 36° total, any if I move the initial down much it really bogs and loses power in the low end and it SEEMS to want more than 15. The problem, my idle is too high. I took the carb off and set the secondary and primary blades so I have just the square of the transfer slow showing. I set the curb idle screw so that it was basically backed out all the way when you could see just the square. Now when I back the screw out all the way with the engine running it's idling too high. Long comment, but is it ok to have less than a square of the transition slot showing? Or even none of it? Basically when I set it by eye with the carb off and I have a square, put it on, it idles too high.

How do you do this on a 2barrel Holley carburetor? you can also drill a small hole in the throttle plate to get the same results.

does this also wotk with a brawler quick fuel double pumper and manual choke and manual secondaries

You were a big help thanks .

what size holley carb do you have on this post

How do you adust the throttle blades to only have the little square part of the transfer slot showing?

So how do you set idle on a 350 2 barrel with no secondary?

Can this adjustment be made with the Carb installed ?

What exhaust are you running on your car?

Will this work on dual carb tunnel ram? Sideways mount????

Just asked on another one of your vids, what does setting to square mean. This explains it. Thanks

Any setting over .020 on the slot will cause a very rich idle. You can purchase the Billet base plate from Proform that has a screw on the top side of the secondary shaft for this adjustment. Its just like an idle screw. Lots of people dont want you drilling their primary shaft blades.

With my big cam vortec everything square the motor won't even run..... No messing with timing will fix a motor that has under 5inch of vaccum at idle. Would drilling holes in the throttle plates be the way to go with mechanical secondary on a Holley brawler carb. Instead of messing with the secondary throttle blades to let in more air and increase the vacuum.

I have a 318 that I'm putting a 4 bbl street warrior 600 cfm holley carb on. I have no idea what I'm doing but maybe you can help

Very good video, thanks

Hey man, Getting ready to try tuning the carb on my truck I just finished touching every nut and bolt on. I got it to fire up and put around but it's really bad. Had a question though, some of your videos contradict (or rather, use different methods) to setting idle. Sometimes you say use timing, in this you say use secondaries. Which would be the proper way? Are you still tuning your idle with the secondaries mainly? Should I aim for keeping those closed and trying to set idle with timing first, then if I need adjustment, use the secondaries? Thanks a bunch

Nice video. Good info, will give it a try when it's time to assemble my rebuild engine. thx

Very good on setup of Idle circuit. Why do some guys drill holes into the throttle blades?

@ 6:12 is that a wood carb spacer?

Regarding the lawnmower fix(with dirt in the fuel screen), can you make a video that shows how to just take off the gas tank to clean fuel lines, screen, etc. on the exact same Briggs and Stratton engine model that you already have videos of? That would be flipping awesome if ya could! I need to do the exact same thing you did, but I don't want to mess with coil and such...Thanks so much if you do.

Can you do this on an Autolite 4100?

Good info, thanks.

How do you adjust the primary transfer slot? I'm flooding the engine but have no idea how to set this without the idle speed screw.

I got a high cam and I get. Burning eye stinky exhaust. Is it the carb rich or..juzt a HighCam and can't do anything. To make better

Commenting only to compliment intro music !!

will the secondary idle adjustment effect vacuum actuator? ie if closed to far the vacuum diaphragm won't open the secondaries

good idea with the allen key.

Great idea

What if u cant get idle low enough

What size is the allen screw? I'll have to give this a try. I should be able to have less throttle plate opening since I have a smaller cam with higher vacuum as well.

Hey enjoying your videos and learning a lot, thank you. I got a vacuum gauge, put in on port and am pulling 5” of vacuum at idle, so i backed off the idle til the vacuum went down to zero and then added timing til it idled decent but it was then at 30 deg. So I backed the timing down to 22 which was as low as i could and still keep it running (about 600 rpm). I was wondering if you had any advice for me. Thanks I have a Holley 4160, big block Mopar. Mostly stock. Mild cam

Going to overhaul my fuel system, new lines, new tank. I've got a 302, what inline fuel filter would you recommend

What size grub screw did you use so I don't have to pull it apart before I start please.

I have too much primary slot showing and I cant figure out how to reduce it. The idle speed screw is not touching and neither is the fast idle speed screw. What else can I do to make opening smaller? Like a square.

YES-SIR!!! Your motor sounds STRONG! What lift/intake duration does the cam have?

I have a 383 with a 700r4 and big cam... Idle gives 11 vacuum but once I put into drive it idles too low!!! I need it to be at 1400 to be able to drop it into drive to keep it alive... I was told to adjust the secondaries because of the big cam I have.... Any tips?

I was hoping I could pick your brain on a few questions I have

I amhaving a hard time with my Holley carb. How do you set you air/fuel mixture? Mine is at about 1 1/4 out and it just doens't seem right and when I hook up a vac. gauge the gauge doens't even move.

Love it

Love the sound of the car. Instead of a smooth sound idle, yours sounds amazing. Is that because of the cam? I want my 289 to sound like that. Please suggest cam, exhaust carb set up!

Ive heard time and time again about adjusting the transfer slot exposure even on new carbs. What doesn't make sense to me is if it's so important, why isn't it set "correctly" from the factory right out of the box? I ask this because the new carb i just bought didnt have the transfer slots setup like Ive seen several content creators suggest.

But if the tranfer slots are squared when set and the butterflies are closed, were will the motor suck Air from???..

I know this is old but is that a piece of wood for a spacer? Looks like a wood grain on the side of it.

This adjustment is also called the " cold idle cam adjustment" right? It is this adjustment that sets the cold idle-up when you 1st crank your engine right? Sorry man.. I have a 64 Fairlane and the previous owner half-ass installed the Holley 4 barrel and didn't bother even connecting the electric choke wire. He decided that it was just easier to slap the Holley carb on the engine then use the curb-idle to idle the whole engine up all the time to keep it running.. I am NOT a mechanic (and don't want to be one) but I am now forced to try to fix this problem myself (and Im getting pretty good at this I might say) lol .. I have my electric choke connected properly and my butterfly opens up to full as the engine warms up but unfortunately the engine doesnt idle UP when cold in order to keep it running. I have to sit in the car and tend the accelerator until the engine is warm enough to run on its own then its idled way too high of course.. I have the engine warm idle pretty much adjusted now. Now all I need to figure out is how to get the engine to idle-up when cold or (first started). Shit am I even making any sense? I am so sleepy as I am trying to research this shit. :( Thanks for any help you can give me man.

do u set idle air mix in gear for automatic as holley recommends or 750 rpm in park is okay?

What causes it to pop on Acceleration

So I have the 4160 vac secondary. My idle mix adjustments have no effect. I set primaries to have the square. Can’t remember what secondaries are at (not with truck). So does the secondaries need to have the square too or should they be closed at idle?

Hey there thuunderhead , how come no one tells us to WATCH how many turns or turn in my case were your idle transfer slots are correct ? Then you no 1 turn in from contact which is when most holleys are squared on t slot ,would not have to remove carb great info as always

gold

Use a screw with knob on the end

Excellent, excellent video, though you did tap the gold butterflies in the beginning of the video and said they were the primaries

Can I have your Galaxie? Thank you in advance!

Song name

This is probably why I'm rich at idle

I dont think I would tell anyone to change there idle by adjusting you timing lol

Great information. Just invest in some lighting.

Yeah DO NOT set your idle by adjusting your timing