General Category > Quadrajet Carb Talk and Tips
carb questions
old blue 75:
Yup you have to pay attention we ordering pistons. Stock sbc 350 is 1.560 pin height, there are 1.540 and 1.550 pistons out there. I figured this out to late.
old blue 75:
Finally got back to this carb.
I found a 1 1/16"- 20 tap on ebay and made a replacement fitting ( and made a inverted flare cutting tool to finish the fitting). Taped the casting and refaced the seal seat. I did a pressure test with a plugged seat and air hose hooked to a short piece of fuel line. At 20 psi did not see bubbles in my soapy water. Is this a good enough test or is there a better way?
Cliff Ruggles:
20 psi and no bubbles/leaks it will be fine...
old blue 75:
Ok cool.
Moving on, I have the primary shafts bushed but will need screws.
I measured the primary metering rods and they seam to be the 74 back
long style. The part number says 1975. Was 1975 a transition year?
The primary rods have flat spots worn on them, I did not see them on
your site do you not have them?
Here is info on the carb.
Idle tube .044
Idle down channel .053
Upper idle air bleed .092
lower idle air bleed .063
Idle bypass .097
mixture screw hole .074
Air bleed main body .119
Air bleed air horn .120
main jet .071
primary rod .026
secondary air bleed .026
Secondary air flap 1.390
Accelerator discharge holes .053
Secondary accelerator wells .034
J hanger CP rods
Also what is the life expectancy on choke pull offs.
The one I took off is good but I have had it sitting on the
shelf for 10 yrs plus and who knows how long it was on there
before I got it?
Thanks
Kenth:
7045214 is a 350 HD Truck 4M Quadrajet.
This unit have 39B primary rods from factory.
Only M4M uses the shorter primary rods.
Check the "accelerator discharge holes" or secondary POE again, the restriction is located a bit in from the .053" exit.
SB Chevy Qjets uses .042" restrictions, most BB and some HD SB units uses .035".
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