Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

427 BBC Carb help

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dntoearthman:
New to forum so any good advice is appreciated : I am having trouble getting the carb professionally built in a timely manner if at all.  I do feel  comfortable doing the modifications needed but have no idea where to begin with jet size, metering rods, bypass tubes ect. I did purchase one of Cliffs books.
I do not have the current carb set up on hand but I could pull the carb down and find out.
The  carb is supposed to be a  1979 800 cfm quadrajet
#17057512
2466 APH
I  purchased from SMI 5  years ago and was  set up for a mostly stock 427.
The new engine build is listed below. Currently It seems to run fine but I do have idle quality issues. This may just be partially due to the cam as it has a very rough idle- it is running on the idle ckt with about 17" vacuum. I run full time vac advance with it  unplugged I have 15 deg initial mech advance. I can pull the vac line going to dist adv the idle speed will stay almost the Same if I plug that port with no vac advance the drops significantly. I can cover the throttle body and will die, the 2 idle adjust screws seam to work as they should.

1968 Corvette 427 BBC
TKX 5 speed trans Close ration 2.87 1st  with .62 5th gear
3.36:1 rear end
Bored .30 Over
Forged small dome pistons
Oval port close chamber heads with small stem valves
1968 Factory 390HP Spread bore dual plane Alum Intake headers Comp roller rockers std.

STR BBC288-... BBC Retro Fit Camshaft
Adv. 288/300
.050" 229/241
LIft 600/570 with 1.7
109 Lobe Sep
(( Bin - 1Q5 ))
Piney Flats 1V4 399.00 399.00T 1
MMS 5374 PAIR#5373 BODYD .842 ROLLD .700 BBC .842D T/B STREET PERF HYD ROLLER Thanks in Advance Mike Hirtzer
931-623-4885
Nashville TN 37221

Cliff Ruggles:
109 LSA is going to have a "rough" idle.

What is the idle RPM?

How much timing is the vacuum advance adding at idle?

Since the carburetor was supplied by SMI I'd take it apart and see how they set it up.  IFR's, DCR's, MAB size, IAB size, bypass air, jets, metering rods, etc.

Over the years I've had scores of carbs sent here built by SMI with issues and pretty much threw everything they put in it out and started from scratch.

Any pics of the carburetor that you can post?

77cruiser:
Is the 17" vac. a typo? 12-13 could be about right maybe.

dntoearthman:
You are correct about Vac its a good 13@Hg-  Well my timing light just went K=PUT 
After ready your post Cliff I'm not so sure about my skill set in doing the modifications necessary and would love to have THIS ONE SET OR OR PURCHASE ONE? Is this something you could help me out with?
Attached pic but you may have wanted others

dntoearthman:
Also if I pull the full time vac advance off the carb I have to turn the idle adjustment screw in so for to get it to idle it comes off the idle slot.

THX Mike

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