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Thread: Rochester Carburetor
03-24-2009, 02:01 PM #1
I have a rochester 4bl carb on my 77 pickup. Just had it rebuilt and was wondering about the mixture screw. I remember years ago I used to hear that you screwed the mixture screw all the way in ant then backed it out so many turns. Does anyone remember this?
03-24-2009, 02:32 PM #2
Best way is with a tach but the old tried and true way is to turn it in slowly till it misses <this is a lean miss> then back it out 1 turn.Jim
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03-25-2009, 11:37 AM #3
My carb is a 4MC and I can only find the idle screw on the driverside in the front. Where is the mixture screw located?
03-25-2009, 12:15 PM #4
i had to do this to my 84 monte ss. i played it by ear and it worked well2009 cobalt ss, imperial blu metallic, lsd, dejon powerhouse intake, Dejon bpv spring upgrade, Trifecta tune, clutchmasters aluminum flywheel, clutchmasters stage 1 clutch, 20% tints,
2008 avalanche ltz, imperial blue metalic, k&n cold air intake, Gibson cat back duel exhaust
03-25-2009, 12:25 PM #5Gary
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03-27-2009, 02:13 PM #6
Thanks, found the screw and did what you said!!!
03-29-2009, 10:36 AM #7
I started this thread and thought I had solved the problem, but have one question. I located the screws on the base of the carb. One is on the drivers side base and the other is on the passenger side of the base. Does anyone know which is the idle and which is the mixture? I looked on line and found one source that told me they were both idle screws!
03-29-2009, 10:45 AM #8
Correct Charlie, they both are mixture screws.
03-29-2009, 10:50 AM #9
Should they both be set the same?
03-29-2009, 11:00 AM #10
Yes they are exactly the same. There's one for each primary. Adjust them one at a time then recheck them. When you turn them in you are going lean. Once the idle is good you're done!
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