When the engine is cold, the secondaries on the carburator don't kick in. When the engine is warmed up, they do kick in. Is this normal? Will it get better if I rebuild the carburator?

That is normal.

There is a locking lever on the right side that engages the rear throttle shaft when you pump the gas (setting the choke) during a cold start. When the choke is fully off the lever will drop down releasing the the rear throttle shaft. You really don't want your rear throttle blades opening up when the engine is cold anyways. Not a good thing hammering the 4 bbl wide open on a cold engine.

Sarge

I haven't hammered it cold except for once and that is when I noticed it and wasn't sure if it was supposed to do that or not. I thought it was designed to do that but had to make sure for my own knowledge. Thanks for the reply.

Now that I have a new exhaust on the car, I need to rebuild the carburator. How hard is it to rebuild? I bought a rebuild kit for it but not sure how difficult it is to rebuild or how long it should take. I did notice that there is a plastic cover the air/fuel mixture screws and it wont allow me to adjust this. Do these just pop off for adjustment and can it be put back on?

Before you tear it apart, check the primary throttle shaft for freeplay. Do this by grasping the throttle linkage (where the throttle cable hooks on) and try to wiggle front to rear and up and down. If you have a lot of slop there, that creates a vacuum leak and will give you problems when you go to set the adjustments for A/F and idle. There is a company (I'll have to look it up later) that sells the bushing kit to fix worn throttle shafts. This is a common problem with Rochester 4 bbl carbs.  As for the plastic screw limiters we use to just break them apart with needle nose pliers. They are brittle. Just be careful not to bend the mixture screws.

Sarge

Go to Vetteprojects.com  

Click on Ken's Projects and the links to QudraJet rebuild.    There you will find step by step procedures to rebuild the q-jet, complete with pictures.

Those are from my 75 L-48, exact match.  My photos and text.