Carb tuning 101

[78Suburban]

I'm wanting to fine tune the Idle mix screws on my ebrock performer. I know I can back each one out till I see a small increase in RPMs, but I don't have a good tach that I can simply plug into the motor. Can I just use a vaccume guage and turn each screw untill I get the highest vaccume reading? What is a good vaccume number to look for?
thanks,
James

 

[jaredmajor]

Yeah the vacuum gage is the other way to do it. Or by ear with the rpms. I have a tach, but i do it by ear. Vacuum readings, you just want the highest vacuum reading, this will all be dependant on what cam you are running, bigger cam lower vacuum at idle.

 

[78Suburban]

is using vaccume a fairly precise way to do it? Should I turn them all the way in, then 2 1/2 turns out and start tuning from scratch, or should I simply try turning each screw in and then out and see what raises the vaccume? I know I need to do one at a time.
thanks,
James

 

[Chevy305]

I use a vaccum gauge and it is dead on balls accurate. I recomend turning both screws 1/8th at a time. The goal is to achieve the highest vaccum.

 

[mrk5]

Definitely no more than 1/8th of a turn. One time a mechanic showed me on their fancy tailpipe machine the difference a minor turn on the mixture screw can make. I was surprised.

 

[Triaged]

I use a WBO2 to tune them

www.wbo2.com

 

[norville]

I'm pretty sure E-brock has a procedure for doing it. I thought it was 1 1/2 turns out and go from there.

bob

 

[littlejimmythatcould]

I agree with the 1 1/2 turns before you start tuning. A metering rod kit would help fine tune it even more. Also adjusting your accelerator pump to your personal needs could help too.