Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Quadrajet 7042220 idle air modifications

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Tway:
So I bought the SR rebuild kit from Cliff along with his book for my quadrajet 7042220 which is for my 72 chevelle 454. I wish I had bought the idle air tubes since my collars were driving down with the tubes. I had to drill the tubes down a bit to get a screw to grab the collars. Anyway just another delay since I’m in Canada and getting stuff shipped is slow.
I measured everything but have no idea if these were ever modified over the years since I can’t find any info on what the measurements were from factory. Also not sure how much to modify the air tubes and holes behind the mixture screws.

Idle tube .043
Idle down channel restriction .046
Upper idle air bleed .069
Lower idle air bleed .078
Idle bypass air .142
Mixture screw holes .081
Main air bleed .120
Fuel inlet seat .130
Secondary rods CM
Rod hangar H
Primary rod 49B
Primary jet 77C

Engine is presently at John and allyn Armstrong’s being rebuilt.
.030 Keith black pistons with -12.00 cc head.
Stock rod length 6.135 and stroke 4.00
Roller set up cam/lifters/rockers
Comp cams extreme energy roller cam 226/242 @50 and 110 lobe separation
The stock 3999241 heads had 113.06 cc chambers and 2.06/1.88 valves
The valves were increased to 2.19/1.88 with some mild porting.

Kenth:
Your measured dimensions are about the same as I found in at least 3 untouched 7042220.
Not much that needs to be changed on it for your engine, but .095" holes for the tips of the idle mixture screws and .052" holes for the secondary POE holes as well as .052" holes for the idle channels could be suitable.

Tway:
Thanks for the reply Kenth.
So for secondary POE is this these holes in the pic just above the pick?
And .052 for the idle tube and also for the restrictor?
I’ve also attached a pic of my idle air tubes and I assume these can’t be shortened and used (if I can get the collars down further)

Kenth:
On my pics the idle down channels are marked red (between idle fuel tubes and accpump channels).
On the other pic marked yellow you see the secondary POE (the actual restrictions are a bit into the holes).

Your .043" idle fuel tubes are fine. FYI these are the tubes with the collars (they are NOT idle AIR tubes).

HTH

Tway:
Had a brain fart calling those collared idle fuel tubes an air tube but thanks for clarifying and showing me where to drill.
So for me to reuse those idle fuel tubes am I correct in thinking I have to get the inner tube up flush with the top of the collar?

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