Carburetor Rebuild - Rebuilding The Electric Q-Jet
Those '80s GM Feedback Carbs Are Probably More Than A Little Crusty, So Here's The Performance Skinny On Rebuilding The Electric Q-Jet
Bush It
One classic problem with Q-jets is a loose primary throttle shaft. SMI sells a bushing kit that is easy to install and will really improve throttle response and driveability. A classic symptom of a worn primary is excessive idle rpm-even with the idle-speed screw turned all the way out. The procedure is easy to do yourself, or you can send the carb to Murphy and he'll do the restoration for you.
Use a small grinder to remove the small stakes on the throttle shaft screws. The ends must be ground down or it will be nearly impossible to get the screws out. Don't bother with the secondary shaft. It rarely is worn.
Remove the primary shaft from the throttle plate.
The passenger-side bushing can be lightly tapped into place with a hammer.
Rochester stepped the hole in later Q-jets, requiring you to carefully drill the driver-side bushing hole with an 11/32-inch drill bit. Work slowly here and only drill down deep enough (usually 3/8 inch) to accommodate the bushing.
Tap the bushing into place and then use the supplied reamer to carefully size the bushing to allow the throttle shaft to turn easily.
Use a small amount of thread-locking compound on the new SMI screws for the throttle butterflies. Carefully position the butterflies to fit as tightly as possible to the throttle bores. The test is to hold the baseplate up to a light source to see minimum light around the butterflies with the throttle closed against the idle-speed screw.
Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!