Hey guys. I just bought an 85 z-28 for my wife. I have always had tpi/tbi cars before this. We did a full tune up (car only has 120k been sitting off and on its whole life) the coil was origional, everything else was close. It runs great until we took it to the track, at full throttle it runs strong from take off to about 100 feet then starts breaking up until you back off of the throttle . I then changed the fuel pump and filter and no difference. Do I need to rebuild it/have it rebuilt. Are these carbs bad to rebuild?

 

You could still have a fuel delivery problem. The pickup in the tank has a sock on it that can get clogged. You need to do a fuel pressure and/or fuel flow test on it to be sure.

You may want to also check the operation of the air valves on the secondaries. With the engine off, they should move freely with a slight resistance, and go back closed on their own. When opened, they should also pull up the secondary metering rod hanger (and rods) smoothly - the AV cam that does that has been known to fall apart, so it is worth checking to make sure you aren't chasing wild geese.

If all of that checks out, the carb isn't that bad to rebuild. You need a special tool kit (~$10 from most parts stores), and a multimeter to do the adjustments. Other than that, it's pretty much a rebuild like any other.