CP888

I have a 1970 olds 350. I just replaced my worn out quadrajet with a new jet performance quadrajet (part number 32002). After installing it I adjusted the air/fuel ratio screws. Initially the secondaries would not open at all so I adjusted the tension on the secondary butterfly. The secondaries now open but it is performing poorly even compared to my old worn out one. If I floor it i can hear the secondaries open but my car revs to about 3000 rpm and very slowly increases rpms after that. Before it would climb quickly to 5200 rpm. Am i missing something to adjust? Or what do i have to do to get this carb working properly

67442nut

You may have taken too much spring tension off the secondary butterflies.
The small blocks require tighter spring tension than the big blocks.
Try adding tension in small increments to see if the problem improves.

joe_padavano

Those are not "secondaries". The secondary throttle plates are on the bottom of the carb and are mechanically controlled. They open all the time. The things you are looking at are the secondary air valves and they only open in response to mass air flow needs. If you based your "would not open at all" statement on looking at them while revving the engine in park, you usually WON'T see them open. They only open under load, which is how they are supposed to work. As noted above, you need to reset the air valve spring wrap, as you have loosened it WAAAAY too much.

oddball

IIRC, the starting point for spring tension is loosen the set screw, loosen the spring screw until the air flaps fall open, tighten until they close, then tighten another 1/2 to 3/4 turn. Fine tune by driving - loosen in small steps until you get a bog off the line, then tighten back.

You may be best served by getting the Doug Roe and/or Cliff Ruggles book and going through the tuning section. Alternatively, get a parts store rebuild kit and follow the base setup instructions in there.

Don't assume that Jet actually set the thing up correctly. Or built it correctly. I don't have any first-hand stories about Jet, but I don't trust /any/ large carb rebuild shop.

hookem horns

Assuming its a TH350 automatic, is the kickdown cable connected and functional? Stock was connected to the gas pedal but it could have been set up Chevy style and connected to the carb.

joe_padavano

This is probably good enough for a carb mounted to the intake, but the right way to do this is to take the carb off, turn it over, and look at the spring. The factory method is to loosen the spring, then with the air valves held shut, turn the screw until the end of the spring just touches the pin on the air valve shaft. Then continue to turn the screw the amount specified in the specs for that particular carb and tighten the lock screw.





As noted, Jet carbs tend to be set up for a Chevy. No guarantee they will be correct for an Olds, especially one that is not stock.

CP888

The jet carb i purchased was specified for buick/olds. I will try adjusting the flap properly this weekend. It doesn't seem to down shift like it did with my old carb so I will have to check that cable unless the wrong flap tension can prevent a down shift. Thanks for the help

Fun71

There should not be any ambiguity about this - it either downshifts or it doesn't, and it should be fairly obvious either way.

When you installed the new carb, did you ensure the throttle linkage pulled all the way open when the gas pedal was pushed to the floor? The original cable bracket on my '70 Supreme was held down with just one bolt on the drivers side rear of the carb and sometimes would slip a bit so the carb didn't actually go WOT when the pedal was pushed down. It took a bit of adjusting to get it set right. I eventually located a bracket that was held down by both rear carb mount bolts so it couldn't slip. It's something to check on while you're doing the carb adjustments.

CP888

Got it running great now. I adjusted the tension properly and adjusted the kickdown cable since it was not being pulled fully at full throttle.

oldcutlass

Well done, now on to the next project.