1971 qjet Air Bleed, Primary Rods, and Jets

[71vette]

I have a 1971 Corvette with 454, manual trans, very mild cam.  I've built a couple of 1979 Q jets for it using Cliff's procedures and they work great.  However, I'd like to use my original carb since the car is very original. 

The original carb has the huge main air bleeds .119 and 77 jets with 49B primary rods. It also has .134 idle air bypass ports.  It suffers from nozzel drip. I've put new primary shaft bushings in and checked the other specs for idle down tube size etc. and the sizes are close the the maximum Cliff has in his recipes.

I was wondering if about installing Cliff's smaller air bleeds to cut down on the emulsion air.  If I do that, I don't think I can use Cliff's .044 primary rods and jets because those are for 1975 and later carbs.

On these older QJets, should you leave the air bleed sizes alone? 

[73 Z28]

Here's my suggestion. Observe the current travel of the primary metering rods. To use cliffs primary rods in a 71 q-jet, you could shim the power piston travel with some small washers to get the same amount of travel as with your current setup because the 71 uses a different style APT then the 75 & later carbs.. Then you could use the bushed air bleeds and jets accordingly. Make sure that the washers have a hole in them to allow engine vacuum to act on the power piston and verify that there is no binding of the piston in the bore.

Paul

[73 Z28]

This is a correction to my last post. Compare the overall length of the primary rods and if Cliffs are longer than your current rods, then shim the power piston to get the proper rod/jet relationship, but if the rods are shorter, you'll have to trim the pin on the end of the power piston or have a custom set of rods made.

Paul

[Cliff Ruggles]

We sell the correct length metering rods for those carburetors, plus the jets and either press-in or screw in main airbleeds.

I set those up all the time with the smaller MAB's, duplicating the calibration of the pre-1970 big block carburetors.  They work much better everyplace than the large MAB set-ups....Cliff