Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

17056228 First Test

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blazer74:
Hello.  Just completed rebuild on 17056228 large primary bore and mods using recipe #1.
Used Cliffs S/R kit + 2ndary spring and cam kit,  rebushed primarys, Small notches in 2ndary flaps for Poe. Bushed main air bleeds to .070 airhorn and body from .120
Idle tubes .036
Channel restrictions replaced to  .047,  previous  .055.  Slightly larger than  recipe calls for but thats the size the replacements were, driven in slightly below main bleeds
Upper Idle bleeds .069,  lowers .076
Bypass air .080,  Acc pump disc holes .026
Poe Wells .039, Poe  Discharge holes  .052,   2ndary bleed tubes .036
Green power piston spring,   1/4 float level
Cliffs 44 Primary rods,  72 jets, K hanger and CH rods.  Pulloff at 2 seconds.
Mix holes .089


On first start up after warm up Idled slightly ruff (Choke completely off). Had to adjust mixture out 5 + turns min to get 14hg and a better idle, peformed Tip In (2000rpm) and had to adjust ADP up 5 turns to get slight rpm increase, after 5 1/2 to six turns no increase and less than 5 turns out get larger  increase.  Do not get rpm increase when removing small vac line.
Idles at 700, 650 in drive.    Has a slight stumble off idle with light or hard throttle input,   Acc pump shot is immediate and strong.  Exhaust stinks,  Runs strong otherwise, no hesitation at cruise, smooth transition to secondarys with a slight bog when open with spring at 3/4 turn.   Had to put truck away and go to work.

Note: If ADP is less than 4 turns out will get lean pop when snapping throttle.
Idle is just  slightly rough and stinks bad.  Power piston is down at idle and 2ndarys closed tight. No  apparent vac leaks.

Suggestions? Larger jets?

Thanks Craig


74 Blazer    355,   292 adv 214@50 449 lift, 111 lsa.   Performer intake,   stock 882 heads, flat top pistons.
                   Headers and dual exhaust 2 1/4.  2000 stall, 4:10 gears   35" tires.   Timing 10 initial. stock     vac adv can,  Hei distributor   

Cliff Ruggles:
I slight stumble at light throttle is usually part throttle fuel to lean.  Raise the APT a tad more and it should correct that problem.  If not, go up one jet size and test it again.

Always set the idle mixture screws for the best idle quality at the leanest settings.  This is done by turning them in until you get a slight drop in engine rpm's, then back them out about 1/2 to 3/4 turns.....Cliff

blazer74:
Thanks for the reply Cliff.  Figured as much with larger jets,  I had 73 jets in it at first but opted to 72 before I installed the carb. One of those unwritten rules first instinct.   Going to swap jets and see what happens.   Never had to turn mix or adp out this far before.


Thanks again for your time,  Craig

Cliff Ruggles:
Nothing at all wrong with running the APT our 4-5 turns (or more) to fine tune the primary part throttle A/F.

All that means is that the metering rods have LESS distance to travel when more power is called for (vacuum falls off sharply)......Cliff

blazer74:
Hey Cliff,    Progress.      No help raising apt , went with the 73 jets no help with stumble. It did give me NO control of apt during tip in.    So I disconnect acc pump and problem gone, tried outer hole and a little better but too much pump shot.  Mix still about 5 1/2 turns out and can kill engine with needles turned in as the same with the 72 jets.
What do I do about too much pump shot, Holes are at .026,  and should I go back to the 72 jets also?     


Thaannkks!    Craig

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