I had my q-jet rebuilt by fred cattlin a few years back and had it off the car to try a holley. I put it back on this weekend and it fired right up and idled great after 2 years of the carb setting under the work bench. What i did notice is that the holley seemed to rev way quicker when the throttle is cracked in park and the secondaries open. The carb is on a 1970 350 buick in a 1976 skyhawk (mid 12 second car) The paper work that was sent back with the carb said. 43 44 70 72 k hanger bz rod I hope to get to run it at the track this weekend and see how it runs compared to the holley i just took off. Does that jetting sound good for a 750 q-jet
As I recall, the "jetting" in the secondary barrels is always .135, with the metering rods being the control. The primaries will be jetted to the application, not carb specific. Such things as engine size, source and emission package will determine jet size and metering rod package. The final control is the power piston spring, which controls its response to changes to manifold vacuum. ALL of these factors will affect fuel metering. One point concerning me is the fact that the jets are uneven. That does not happen frequently. Ray
Jetting A q-jet has two primary jets. Each primary jet has a metering rod that hangs in it and is held down by engine vacuum. This reduces the fuel flow when vacuum is high and allows extra fuel to flow when the engine is under load and experiencing low vacuum. It looks like this carb is set up with staggered jets. In other words, there are only two primary jets, and they are usually the same size with identical size primary metering rods. Your tag indicates "43" and "44" which are both primary metering rod sizes as well as "70" and "72" which are both primary jet sizes. I think you may have a 70 jet with a 43 rod on one side and a 72 jet with a 44 rod on the other. I imagine this might be an attempt to compensate for differences in fuel distribution between the left and right carb barrels. Or maybe the tag doesn't mean anything. The other part of the tag relates to the secondary metering system. All Qjets have 0.135 cast in "jets" for the secondary. The amount of fuel allowed through the secondary is controlled by a pair of secondary metering rods. As the secondary air valve on top of the carb opens the metering rods are lifted up and allow more fuel through the jets. There are differences in the rods taper and tip size. The thinner the tip the more fuel at WOT. The more gradual the taper the more fuel at part throttle. There are also differences in the rod hangers. Hangers are lettered, with the difference being the height of the rod - some hangers hold the rod lower in the jet and delay the fuel enrichment in relation to the air valve opening. I think that the primary jets/rods are pretty close to stock sizes for a 350. This information should be available in a shop manual or maybe online somewhere. I can't tell you much about the secondary rods and hangers as regarding a 350 Good luck, and I hope this helps.
