Can anyone tell me how to do this, how much it would cost to get this done, how long it takes and what it does? Thanks!

 

It depends on what carb you have. Holley is easier than a quadrajet. Changing the jets will alter the amount of fuel metered into the engine across the rpm range, from idle to wide open. Jets are numbered according to the size of the metering hole, small number=small hole, bigger number=bigger hole. However, if your problem exists only in a certain rpm range, jets will not cure all your problems. For instance a rich condition at idle will only get worse with larger jets. Also, if you have a quadrajet there is also the metering rods to consider, they change to metering area of the jets according to available engine vacuum.

Cost can vary depending on type of carb.

If you don't have any experience with carbs or someone to help that does you should have it done by a shop you trust. Engine fires suck.

 

your problem will be that they aren't going to be able to just change your jets. to change the jets, a competent shop is going to want to go through your whole engine, give a full tune and then do a little experimentation with different jets and power valves (and possibly air bleeds). this might sound a bitlike overkill, but I'm sure they don't want you to come back saying "the thing really still isn't running right". their name and reputation is going on their work, so they are going to want to make sure everything is perfect

you definitely want to find a shop that specializes in that sort of stuff, because a shop that just works on factory carbs, isn't really going to be any good at a high performance tune