General Category > Quadrajet Carb Talk and Tips

70-74 Cadillac Qjets

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Cliff Ruggles:
The Caddy carb will have very small MAB's and small jets.  Those big engines weren't all that efficient so the carbs used on them are designed to pull in a lot of fuel with a much weaker "signal" from the engine.

Conflicting information on the rear located holes in the flaps, they were used on some Marine units as well.  For sure it would be more advantageous to have POE holes or notches much closer to the exit holes.

The big Caddy carbs used very small secondary metering rods for the most part, once again those big engines weren't overly efficient so love a lot of fuel coming down from the carb.......Cliff

mcx:
...it's official carb # 7043234
Primary jet 68 (I think ?)
Primary rod 41B
Secondary rod DF
Hanger N
...today I attempted removal of the APT in the base plate...I used your advice heating it up with Mapp gas and used transmission oil to soak in as it got really hot...used a snug screwdriver and tapped with hammer and loosened and tightened and repeat...it came out!!...I installed a mixture screw to test it out and it works ok for now...I partially assembled the carb just to see the range of adjustment of the primary rods in the jets  and am impressed what it can do.

429bbf:
for what its worth i had a 76 eldorado  472 or 500 i don't remember that car got excellent fuel milage . it would do 18 all day long and climb any hill in wyoming with out any effort . my neighbor had the same car with a 350  it was a gas guzzler he got about 11 tops . we used to race stoplight to stoplight won a lot of races and destroyed a brand new set of bridgestones in less than 2000 miles . man them were the old days .

mcx:
...I believe a 472 Eldo might get 18 miles per tank..LOL...cool cars.

....I spent the morning recording measurements as best as I could , wish I had a better set of bits.
Air horn:
Main air bleeds .05ish ..guestimate as the closest i had was .047"
Primary POE discharge shooter holes... .033"
Idle air bypass hole (passenger side  primary bore)... .1094"
Idle air bypass in driver side primary bore was usual notched out section.

Main body:
Upper idle air bleed... .05ish, as close i i could get.
Lower idle air bleed... .067"
Idle down channel.... .048"
Idle tubes....still have to pull.
Secondary POA well holes.. .039"
Idle air bypass  .1719"

Base plate:
Idle mixture screw holes. .0625"
Idle air bypass hole.. .0938"

mcx:
Cliff...another question regarding those secondary Air horn flaps with the unusual rear cutouts,  do you think those are designed to open slower? I would think there is less leverage  on the longer side of door to open quickly.

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