Holley Carb - Setting Idle Speed Correctly

the Proper method to set your idle speed on your holley carb.

[williamcharles]

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.

[Corvette]

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

[HeadFlowInc]

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! 👍👍👍

[chrishansen]

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!

[briantarka]

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.

[novaguy]

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

[eddiemrfixit]

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

[-V.T.L-Machinist]

Your tutorial really helped me adjust my 670 holley. Thanks

[scotthunter]

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.

[basshead]

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.

[FordCoupe]

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.

[benwingo]

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.

[walterburaconak]

You answered alot of questions for me thanks!

[paulmarbach]

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!

[americanfreedom]

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

[jimclarke]

First accurate video iv watched, excellent

[donrutter]

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.

[jdcorben]

Awesome video about mechanical secondary and timing 👏

[bowlerbill]

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

[stmustang]

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

This explains it. Thanks