Cliff's Quadrajet Parts and Rebuild Kits

Still running like a top? Have you change anything since you've built it? Been staying out of trouble?

The ignition coil is new, has been working fine.  Let’s assume for now the ignition is working as it should. I don’t want to be chasing 2 things at once.

The tip in test done to analyze A/F mix is quite telling. At 2000 RPM, the APT screw was in all the way, so at max rich. It leaned out further when turned out with measurable drop in RPM and even rougher idle. As it should. I was surprised that it actually affected the mix to that degree.  So in theory if my initial A/F mix is close, this screw can fine tune it from there.

Did the tip-in test. Too lean now. APT screw is at max rich. Increase of RPM went from 2020 to 2280. So an increase of 260. Not the preferred 50-100.  My understanding of the mods I made yesterday increased air slightly (tubes) and reduced jetted fuel 77 to 73 jets.  Guessing a 75 jet may get it closer. The bucking is clearly a symptom of lean air fuel mix.

I’m not sure what down channel restriction does. Can’t find a description on Cliffs book or where it’s located. I’m sure it there somewhere.

Continued from part 1...

Carb #17057204 (750 cfm) with APT

Here's what came with Cliffs SR kit:
Main jets: .070
PMR’s: 44L
SMR’s DA
Orange PP spring
1.5 second choke pull off

I think my combo falls between recipe 2 and 3 so here’s where I’m at, what I’m thinking and what I need help with. Please make suggestions or let me know if I’m off in left field.
Secondary hanger “L”
Air flap open distance: @ 1.28”. Can be opened further if needed
Upper idle air bleeds: @ .068
Lower idle air bleeds: @ .076
Idle mixture screws: Drilled to .094”, no holes in throttle plates
Idle bypass air: @ .081
Secondary POE well restriction: Cleaned/drilled to .040
New Idle tubes: @ .040
Air flap spring: @ 5/8 turn

Here’s where I need help or suggestions.
MAB’s: In main body.  Restrictors are installed.  I believe Cliff suggested .050 in upper and lowers. I’m not questioning Cliff but I may have heard him wrong and they aren’t drilled yet so anything is possible yet.  Does .050 sound right?
Secondary POE restriction: @ .052. Suggestions?
Secondary tube restriction: @ .023.  Thinking .036…Suggestions?
Accelerator pump discharge holes: @ .023. Seems small…Suggestions?
Idle down channel restrictors: Installed but not drilled, thinking .040?
What’s a good starting point for my APT?  It was at 2.25 turns but I never ran this carb so

This is my second q-jet rebuild and I’m actually getting comfortable with most of the terminology and where things are. I’m just a bit confused yet how one thing affects the others. Another 30 years, I may have it.

Thanks
Scott

Looking for some advice on how to finish up my carb mods and rebuild. It’s a long (2 part) post but I want to get all the info out there for the gurus. I sent this same info to Cliff's "Request a quote" messenger but haven't heard anything back yet, so thought maybe this it the proper place to post

I've purchased a SR kit from Cliff including a choke pull off, electric choke, idle tubes, SMR, PMR, brass screw in restrictors for MAB (upper and lower) and DCR, etc.

I'm following Cliff's book and doing all the modifications and suggestions including throttle shaft bushings, 90d primary & secondary openings, air flap adjustment screw. I'm restricting the original large MAB and I notched the air flaps at the fuel holes.

Here are my car and engine specs:
1972 Monte Carlo with power brakes and A/C. My long distance cruiser and spirited driver.
Engine:  350 ci SBC, 1 pc rear main seal, roller block,  9.6:1 CR (measured), zero decked with .039 head gasket for .040” quench, oem 11cc dished pistons
Heads:  Vortec heads (actually Engine Quest vortec replicas), milled to 63 cc chambers, 170 cc intake port, screw in studs, beehive springs @ 95# seat, 150# open, Stainless steel 1.94” int, 1.50 ex valves. Harland Sharp .080” back spaced roller rockers and proper length pushrods for geometry
Cam:  Straub Technologies semi-custom hydraulic roller. .510/.468 lift, 221/227 @ .050, 109d LS, 105d ICL
Exhaust:  1-5/8” long tube headers with 2-1/2” mandrel bent full exhaust with Pypes Race Pro turbo type mufflers, bumper exit. No X or H
Intake:  GM Bow tie, aluminum, dual plane, spread bore, vortec style
Rear end:  3.31 gears with 26.6” tall tires
Transmission:  Art Carr/CPT 200-4r with 2200-2400 stall and no lock up converter
Distributor:  GM points type, vacuum advance distributor with Pertronix ignition module
Timing:  17d initial at 800 rpm, 34d total at 2850. Vacuum advance limited to 10d all in at idle. Cliff feels I may have too much final so I will work with this
Vacuum: 14.5” at 850 rpm idle, 12” at 700 rpm curb. 14” - 15” at no load cruise 2000 rpm, 13” at lite load/uphill 2200-2300 rpm
Continued…