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Author Topic:   carb settings
racer17j
Dirt Maniac

Total posts: 165
posted May 18, 2001 02:42 AM UIN: 54865418
i was just wondering how many turns to set my rochester mixer 5rews at here's what i'm running
carb from a 71 truck 72 jets
480 cam 1.6 rockers@ 37 timing running 89 oct unleaded ethanal i'm from iowa so i don't worry about high elevations and all that stuff just but it does get up in the 90% humidity twords mid season wondering what a good base line would be to start tuning

[This message has been edited by racer17j (edited May 18, 2001).]

KPLugnut
Dirt Full Roller

Total posts: 57
posted May 18, 2001 11:04 AM
Since air quality has a lot to do with this, the best I can do is suggest a general range to start at.
Assuming your butterflies are adjusted so as to expose about .020-.030" worth of the idle transfer slots in the throttle bore, try starting someplace in the range of 1 1/4 to 1 3/4 turns out on each $crew. Many street cars (bone stock, that is) were known to be happy in the range of 2 1/2 or more turns, so don't be surprised if you have to open them further, or even close them down a bit.
Hope that'll get ya started. The best way to perform this tuning step is thru the use of a vacuum gauge and adjusting each $crew until the manifold vacuum peaks, and at the same time keeping the idle within acceptable ranges.

Keep us posted on symptoms or further questions...

KPLugnut

[This message has been edited by KPLugnut (edited May 18, 2001).]

PEDDLER
Dirt Maniac

Total posts: 148
posted May 18, 2001 06:14 PM
The best and most accurate way is with a vacuum gauge. Set each ***** to obtain peak vacuum. Don't worry about how many turns, just adjust to peak readings. An engine vacuum gauge can be obtained at a very reasonable price at the Zone or another discounter.

Pickel
Dirt Freak

Total posts: 239
posted May 18, 2001 09:32 PM UIN: 25419780
I agree with peddler.. thats the only way I set any carb..also check timing as it will mess with the vacum alittle bit..

racer17j
Dirt Maniac

Total posts: 165
posted May 18, 2001 10:45 PM UIN: 54865418
thanks for the tips should icheck it at the bottom of the carb where the brake booster hooks up or on the intake for the tranny line of does it matter?

PEDDLER
Dirt Maniac

Total posts: 148
posted May 19, 2001 03:21 PM
You need full manifold vacuum, not ported vacuum. This means off the carb base below the butterflies or directly from the manifold. I prefer the carb if you can find a port.

The Peddler.

Pickel
Dirt Freak

Total posts: 239
posted May 20, 2001 10:05 AM UIN: 25419780
I run a vacuum gauge in my race car..That way if I have a power loss I know where to start...whether it's a vacuum problem or not.

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