Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
Freshly rebuilt quadrajet flooding from top of carb
gregcarter:
Ok, I measured the secondary slop, and it is about .010. Does that mean that I have to buy a 2nd drill and bushing set?
I installed the primary bushings today, and it feels good. A little snug at first, but after recleaning, sanding the shaft a little, and wd40, it is nice.
The air gap on the throttle plates didn't improve much, the front is tight on both sides near the idle openings and the back seems to touch a little before seeing a sliver of light, then opens up on all four sides a little. I suspect this is as good as it gets, but may indicate that the idle speed control screw had been backed out all the way for a period of time, slightly bending the front of the plates up by contacting the throttle bore.
I measured my tubes today and are as follows:
(as close as I can get it) all are original parts
Idle adjustment screw holes .081
idle tubes .032
idle channel restriction a .043 drill fit, a .052 did not
don't know where the inbetween bits are
main well bleed tubes .025
secondary well tubes .070
main jets .069
rods 36B
sec rods DR
This carb is on a '76 Chevy C-10 pickup with a stock 350 except for an "RV cam", Lift .420/.443, Duration 270/280, and an Edelbrock egr manifold (Calif).
One more thing.... The power valve only had about 1/8th" travel, I thought it had more years ago.. (My old Doug Roe book said it should be around a quarter inch travel.)
This model carb has a horizontal threaded screw between the idle screws, that adjusts the closed power valve height ( I've never touched it.)
I was unable to turn it in to get a base setting, and I had to heat up the area, and grab a small screwdriver with channel locks to rotate it out. It was all gummy in there, and it must have filled up the void and raised the valve. I suppose I'm looking for a beginning height setting, and can set it from there based on info in the book.
Thanks for any help and encouragement you can give me,,
G. Carter
gregcarter:
Better cam specs are 1500-4000\t270 280\t204 214\t.420 .443\t107Deg 117Deg\tB
G. Carter
Cliff Ruggles:
It is not necessary to install bushings in the secondary side, the clearance is needed so the huge secondary throttle plates can fully seat in the bores each time they close.
Nothing mentioned of idle and main airbleed sizes, those carbs came in many configurations. The APT system can be made externally adjustable, we sell an external screw for those.
If your 1902 is the single MAB model it will take a slightly different calibration than the four MAB design......Cliff
gregcarter:
I did some more measuring and reading and have more information for you.
idle tubes .032 (just bought .035 to replace these)
idle channel restriction a .043 drill fit, a .052 did not
don't know where the inbetween bits are
upper idle air bleed .068
lower idle air bleed .062
idle bypass air .039
mixture screw holes .081
main air bleeds (horn) .052
main air bleed (body .110
main well bleed tubes .025
secondary well tubes .070
main jets .069
rods 36B
sec rods DR
float 7/16ths
I was hoping you would either recommend or hold me off the dewarping process. Its probably warped a little over 1/8th".
Thanks ahead for your help.
Greg Carter
Cliff Ruggles:
You have one of the two main airbleed divorced choke models and they left out the lower MAB. Call the shop and order a pair of MAB's, they need to use four .046" MAB's to work like they are supposed to.
7/16" is too low for the float level in that carburetor, move it up to 1/4"......Cliff
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