Fast idle

I have recently bought a silver '79 T-top after worshipping the shape for 20 odd years. I have spent the last 5 weeks buying and reading every book on Vettes that I can lay my hands on to assist me in my quest to restore / modify the vehicle in order to give it to my 6 year old son when he turns 18(at least I gave myself some time.) The biggest problem I have currently is a very fast idle causing it to really thump into drive or reverse when I engage (3-speed auto). There is no more adjustment left on the quadrajet and I have already tried lubricating all linkages. Is there a relatively simple way to fix the problem? Keeping in mind that I live on the other side of the planet (in Johannesburg, South Africa) and picking up spares is not that simple here, should I attempt a repair of the standard carb or simply replace it with something newer / better. I have been looking for an excuse to upgrade both inlet and outlet after reading about tuned headers and a true twin exhaust. My baby is currently stock standard, will carb & exhaust mods negatively affect her value?

Is the Idle fast all the time or just when cold? Do you have an electric choke? I am just learning about cars and engines (I am a mechanic of food not cars as my screen name indicates). so i am just throwing some things out there from experience. I have an electric choke and mine idles fast until it warms up and when i hit the gas the idle comes down, I think this is normal?

Jeff

Thanks for your input, the idle is fast even at optimal operating temperature.

I would look at the timing. The more advanced the ignition timing is, the higher the idle will be. it is not uncommon for people to advance the timing to get more throttle response(free stoplight H.P.).

Timing could be it. Also look at the stop adjustment for the carb secondary throttle plates. It's not uncommon for the secondary plates to hang open just a touch and cause this problem. Also check the fast idle cam, and make sure it's fully releasing, and the fast idle adjustment is not too high.

Ken Styer

have you checked the choke ajustment. its the black disk on the passenger side of the carb. mine was running it rich and also giving a high idle. just back it off alittle and makd sure the notch is between the the othere notches on the disc.