Things to Check
After you've got everything clean, you can check for problems.
First, check the base. Most important is the primary throttle shafts. Move the throttle shaft up and down and front and back. You shouldn't feel any play. If you do, now is the time to have bushings installed. Also check that the secondary butterflies snap shut when you open them and let go. You do not need to check for play in the secondary shaft, just make sure they snap shut when released, and close tightly. Also use a straight edge and make sure the base is flat, or very close. The thick gaskets used will compensate for some warpage, but not very much.
Next, look at the bowl. If you've got bowl plugs like these:
chances are good you do not have a leaky carb. Until about 1969, the plugs were basically mini-freeze plugs and they leaked very badly. After about 1969, plugs like what is shown above were used. You can check these for leaks by using an air gun from the other side and soap and water on the plugs. A leak will show up as a steady stream of bubbles. You can use epoxy to repair the plugs if they leak. I have never had a Q-jet with this style bottom plug leak.
Check and make sure the dowel pins aren't broken off:
There are 2 on the bottom and 2 on the top. If one is missing, it is no big deal, but use extra care when assembling the carb that everything is lined up.
Check the bowl for flatness just like the base.
Last, look at the airhorn. All the brass tubes pressed in should be tight. If one is loose, use the butt end of a scewdriver and tap it back in.
Look at this airhorn:
One of the secondary discharge tubes is missing!
The secondary air flap should be free and not bind, and snap shut from any angle. The choke flap should not stick or bind.
And of course, check the airhorn for flatness.
Other tips.
Use a brake cylinder hone on the accelerator pump bore, it will increase its performance & life.
Save the gaskets and match the new ones carefully, since several will often come in a kit:
