What is the best replacement carburetor for a 1978 Pontiac trans am?

Answer 1

That completely depends on engine size and modifications that have been done to it. Personal opinion is about the only answer you'll get from people here. Believe me, everyone has their favorite carb and can tell you why. I'm going to assume you're running a Pontiac 400. If this is a fairly stock, daily driven car stick with a nicely rebuilt Q-jet. If set up correctly the first time, they are very trouble free. If you have the right person/place set it up, the Q-jet carb can be used in high performance apps and is proven in this time and again. Stay away from 75-76 Q-jets. The idle circuit in them is a little strange and the pre and post Q-jets were much better. In fact, for a decent, street driven car the 77 and up are ideal. Plus they are actually 800cfm as opposed to 750cfm in years prior.

I've not had much luck with Edelbrock carbs...so I'll skip them. A lot of guys run them and have good luck with them.

I've spent a lot of time working with Holley carbs and have run them on a lot of cars. The trouble with a Holley is that you really need to know how to tune them. Jetting, float levels, power valves, secondary vacuum springs, fuel pump squirters and so on. If you have a lot of patience and don't mind learning, or know someone really good with a Holley they are great. With the newer blow proof circuit for the power valves they are also a lot more dependable than they used to be. They run great when properly tuned.

From personal experience, with a moderately built 400 you'll get great throttle response from a 600cfm carb, but you'll run out of upper end power as it just won't let enough air/fuel into the engine. For all around performance 750 does the job really well. Stick to a vacuum secondary unless it is built to the nines. A double pumper just isn't necessary on a mild to fairly well built engine.

The most common mistakes when building an engine is over camming and putting way too much carb on the engine. It has to be a matched setup to work correctly. Good luck and I hope this gives you a place to start.