What is the best way to set the A/F miture on an edelbrock performer carb 750cfm. I don't have any hi-tech equiptment. can u use a vaccuum gauge to set it. Thanks

 

You can use a vacuum gauge to tune the idle mixture if you like. For the others it'll probably have to be trial and error using a stopwatch and a long piece of road. The manual has pretty detailed tuning instructions in it.

 

How do you do it with a vacuum gauge

 

You should have received a litle white plastic T when you got your carb!! You hook this T into your vacuum line and hook a vacuum guage to it!! You increase the A/F mixture screw until the vacuum stops increasing as you turn the screw (my friends stopped increasing at 20...each carb will vary depending on the application) .....once you get max vacuum, turn the screw back about half a turn! That's pretty much it!! Pretty easy!!

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1986 Trans AM
305 TPI
200,000+ miles (speedo/odometer non-funtional! Odometer reads 142,000)
4 Wheel Discs
9 bolt Borg Warner Rear (2.77's....oh joy) :P
Completely Stock
Soon to upgrade to a 355 converted from TPI to Carb, Edelbrock 750CFM Carb, Edelbrock Performer RPM Intake, Hedman Shorty Headers, Stock casting pocket ported heads (2.02/1.60 - 65cc), XE268 Cam, Moroso HEI ignition kit with external MSD Blaster II Coil and an MSD 6-AL Box!!
Current project: Keeping my 305 running until I get my income tax returns!

 

I'll make this easy for you.

tighten the idle speed and both mixture screws all the way in (not too tight) till they stop.

back each screw out one and 1/2 turns.. start tuning from here.

turn the idle mixture screws both evenly till the idle sounds smooth (shouldn't have to go more than 1/2 turn at this point).
(maybe none at all)

turn the idle speed screw til the idle is approx 800rpm (usually tightening the screw).

readjust the mixture screws slightly for best idle.

you generally try to get the idle as low as possible and still be smooth and drivable. This is around 600-700rpm for mild engines with an automatic tranny.

you want the idle mixture as lean as you can run without drivability problems. While adjusting, have a friend inside the car to hold the brake and put it in gear to make sure it doesn't die. When the idle mixture is right it should not stumble or die when you put it in gear.

so your goal is to find a setting with all three of these screws turned in as much as possible with good drivability results.
It helps if you run at least 20 degrees of timing at idle.

with low timing and low vacuum it will be harder to have a strong idle at low RPM and keep the mixture lean. Low vacuum requires a richer mixture-screw setting.

the mixture screws don't always have to be at the same exact adjustment, but they should both be close to one another.

usually this final setting will be around the point of maximum vacuum. That's why it is sometimes helpful to use the gauge during the process... but not necessary.

 

i AGREE WITH 86tpi. That is the "correct" way to set the INITIAL idle mixture. Fine tuning comes AFTER initially setting it properly.

 

I ran mine about 7.6 turns from the bottom with my 350ci. It depends on your application. If you notice it bumping or missing, you are probibly running too lean.

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1983 Camaro Z28
Goodwrench 350ci V8, Edelbrock TES Headers, Flowmaster Catback, MSD 6al and Blaster 2 coil, Edelbrock Performer intake, (Edelbrock Performer 600cfm carb.)- went back to q-jet!!! T5, 373 rear, Eibach springs, Cervin Vega speakers, Rock. Fos. Sub, Pioneer CD,
email-chris4421@hotmail.com
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"I used to be a Mustang Guy! I didn't know the power of the dark side!!"

 

IF it keeps bumping or missing and you are more than 4 turns out, you have MAJOR carb/engine/tuning/vacuum leak problems.

 

Is in rich or lean.

 

IN is leaner idle as it restricts the fuel flow. OUT is richer idle. you should have gotten directions with the carb, no???

 

I run mine at less than one turn out. I've never seen an engine yet that needed more than 2.5 turns.

you would be very rich.

 

That's what I mean!!! That CHRIS guy has some engine problems. 6 turns out and the screw would be in your hand, along with a puddle of fuel! LOL

 

are you guys talking about half-turns or full turns. im in the process of tuneing mine now, and it seems to run ok at about 2.5 full turns out? how do you know when its al the way in it gets pretty tight but still keeps going.

 

the end of the screw is a needle-valve... so don't torque on it.

We are talking full turns. Mine is less than one with a 700rpm idle and 20 degrees of initial timing.

 

No, I don't have engine problems. The motor has less than 2000 miles on it. Edelbrock carbs are just junk in my opinion (not to anger anyone who likes them). I had nothing but problems with mine. My qjet purrs like a happy kitten and the car is faster too. I will post my 1/4 ets sometime next week I hope. I will post my edelbrock times vs. my Qjet times.

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1983 Camaro Z28
Goodwrench 350ci V8, Edelbrock TES Headers, Flowmaster Catback, MSD 6al and Blaster 2 coil, Edelbrock Performer intake, (Edelbrock Performer 600cfm carb.)- went back to q-jet!!! T5, 373 rear, Eibach springs, Cervin Vega speakers, Rock. Fos. Sub, Pioneer CD,
email-chris4421@hotmail.com
-------------------------
"I used to be a Mustang Guy! I didn't know the power of the dark side!!"