menace88SC

i have made the decision to ditch my computer in favor of a straight up carb setup. i currently have the LG4 motor in my trans am with a computer controlled carb. seeing as how this will have to be replaced with a non computer controlled carb, i need to know what the difference is between spread bore and square bore carbs is. i have been told that an eldebrock q-jet is a direct bolt on to my factory manifold, but i have seen them in both spread and square bore. what do i need for my application. i am trying to keep cost as low as possible b/c within the next year or so i will be swapping out to a blown 383 stroker. any help or suggestions are greatly appreciated.

peace,
menace

RB83L69

A "square" carb has all 4 bores about the same size. A "spreadbore" one has much smaller primary bores and much larger secondaries. Generally, the spreadbore design compromises power in exchange for better gas mileage and driveablity, although if the carb is well-tuned, there isn't necessarily much sacrifice.

There is no such thing as a square-flange Quadra-Jet (a product and tradename of the Rochester Prod. Div. of GM), whether it has been worked over by Edelbrock or not. So if you intend to use a Q-Jet, you will need a manifold with the spread-bore pattern. Your factory intake is spreadbore. Any other Q-Jet is a direct bolt-up to that intake, as far as that goes; but then you have to deal with the issue of computer-controlled vs. non-CC. It's an all or nothing proposition: if you put a non-CC carb on there, you will also need a non-CC distributor, and if your car is an automatic, you'll need some method of locking up the torque converter since that's another thing the computer handles.

five7kid

iTrader: (14)

You are confusing the Edelbrock Performer series of carbs, which are square bore and won't bolt directly to a stock manifold, and the Edelbrock q-jet series, one of which happens to be called a Performer q-jet.

If you truly are wanting to keep costs down, your best bet is to stay with the CC q-jet you have now. There isn't anything out there (other than unknown-history used stuff) that won't cost you a few hundred dollars. The Edelbrock q-jets are about the most expensive thing out there, and like RB said, you need to replace the distributor and provide for TCC lockup as well no matter how you go about eliminating the CC carb. For operating effeciency, you can't beat the CC system.

Save the induction changes for the new engine. If you hadn't said "blown 383", I would even say keep the CC q-jet for the 383.