I'd use a Quadrajet, if I could find a good used one to work with. Holley and Edelbrock each work, too, but they have their quirks, which you'll discover as you live with it. Since the Qjet has small primaries and a demand secondary, the standard 750ish CFM size works fine. With the other two, you probably want to go small, perhaps 500 at most. I'd go with a vacuum secondary on the Holley. The Edelbrock has a demand secondary, which helps with smaller engines.
What parts are you using to define the part “mild” ? I ran a 600 Holley on my 225 slant six , a 390 Holley on my 300 Ford six and may run two Holley 94’s on my 250 Chevy.
A stock Carter WCFB or Rochester 4GC will work great and did for years. They will fit on an aftermarket manifold an have electric choke adapters if you want to buy one.
Google is your friend..! There are MANY carburetor sizing calculators on the net. Most all are very similar. While you may think that they aren't correct, by doing the math (the engines volumetric efficiency)...they are. Here's one - https://www.summitracing.com/newsandevents/calcsandtools/cfm-calculator Based on this and many others, a 450cfm or 500cfm carburetor will be more than enough. Any larger, low rpm power will suffer...around town mileage will suffer...no matter what some experts will tell you. Squirrel's Quadrajet suggestion may be good on the primaries, but if you get a larger quadrajet, the engine will fall flat on its face when the secondaries open..! The sort of new, Edelbrock AVS 2, 500cfm is a great choice. Mike
Not if the secondary air door is adjusted properly. Also helps to have the vacuum pulloffs working properly.
Mild 283? Quadrajet hands down. But make certain your intake manifold is DESIGNED for a Q-Jet. Don't even think about considering the possibility of trying to use a square-bore intake with an adapter! If your intake is a square-bore, and you don't want to change it; then either the original Carter WCFB or Rochester 4-Jet would be the way to go. Jon.
I'm running an Edelbrock 500 cfm on my stock 283 & it is just freakin' great. They do require fuel pressure on the lower end & mine did require some float adjustment initially, but it's been flawless for some time. I realize the body on my ride is quite light & I'm running a 4-speed & rear with a gear ratio on the lower side with a free flowing exhaust, but the throttle response & resultant torque is amazing. Every time I drive it, I just can't believe that I'm getting that crazy powerful rush out an old stock unrebuilt motor. I believe a lot of that is due to the carb.
I've run just about every carb suggested above and all have their pluses and minuses. A correctly built and adjusted Q jet gives great all around performance and decent road mileage plus supplies just the air the engine demands rather than telling the engine what it is going to get. I ran an Edelbrock carb on my 71 GMC with the 350 and it worked great with the stock engine right out of the box. You need the proper size for the size of the engine though. I ran Holley carbs for years and still have several hanging in the garage, You have to love them to get them to work right though. They are great if you are seriously into fine tuning but can be a real pain in the butt for guys looking for plug and play with only minor adjustments. I had two wcfb's on the 327 in my 57 panel that I swapped to the 283 in my T bucket. Those can be more than a bit daunting for anyone who isn't trained and experienced in rebuilding carbs. All that said, I am seriously thinking about running a Q jet on the 292 that is going in my 48 for the reason that Jim listed in post 2. They work pretty well with what the engine actually demands and are only going to flow what it calls for if they are adjusted right.
It's a stock cast manifold, 67-68 327-350. Camel back heads 62-69 don't know which size valves. Mild cam. Bought this engine from a friend he said it was low mileage. And from what I have seen on the inside he wasn't lying. The manifold has small ports in front, larger ports in back. A little more info for ya. Going to a car show this weekend and hoping to find a carb at the swap. Thanks for the advice!
OK - wish you would do a spec list in one post, it makes life easier for those of us trying to give you an answer. So here is what I think you have: 283 engine (year and compression unknown) 62~69 cylinder heads (valve size unknown) 1967~68 cast iron factory manifold from either a 327 or 350 Will you be using an automatic or manual transmission? A good general rule of thumb is that you can place a carburetor designed for an automatic transmissioned vehicle on one with a manual transmission, with a resultant slight decrease in city fuel economy. BUT, if you attempt to place a carburetor originally designed for a manual transmission on a vehicle with an automatic, you WILL experience idle issues. A good carburetor tuner can solve the above, with (generally) oversize idle tubes. Some other tuning will be necessary to really dial in the carb. Personally, I am lazy! MUCH easier to start with a carb closer to the eventual state of tune. Check the second line in my signature block. Stay away from the 1965~1967 carbs. They have design issues (all of which are correctable with machine work) and expensive. The major design issues were all fixed by 1968, although the float pin placement is better on the 1972 and newer models (not going to matter on a 283, unless you are trying to get more than 600 HP out of it ). The 1965~1975 units (any that you find at a show for less than 4 figures) will be 750 CFM. Read that as 150 primary, and an as-needed up to 600 more on the secondary. Most of the 1976-up units will be 800 CFM (read as 200/600). GM found (from Carter and Chrysler) that, even on the 307's, transition from primary to secondary circuits was smoother with the 200 CFM primaries. Also, the 1976-up will have better castings, and be less expensive. Stay away from the 1980's with feedback. The closer the displacement of the engine for which the carburetor was designed to you 283, the easier the tuning. Apologies to the moderators for discussing a non-H.A.M.B.-friendly carburetor in detail, but the OP is (I think) putting it on a H.A.M.B.-friendly vehicle. Jon.
You are good Jon, just keep typing and we keep learning. Your insight is always appreciated. Regards, Randy Sent from my iPhone using H.A.M.B.
Jimmy , The 66 327 /275 could be bought with rhree different carbs Holley, Q-Jet, and AVS. Three different manifolds.
Squirrel is correct about secondary air door adjustment. My brother explained that to me around 1977. If secondary’s open to soon engine would stall. Allow vacuum to build before air door is able to open so fuel is atomized. He knew what the hell he was talking about when he flipped the Q-jet over to expose the hidden adjustment screw. When he was done tuning my engine it would light the tires off at every light.The cops would pull me over just to see what was under the hood. I now run around with The secondaries blocked off in my 73 k10 Suburban with 454. It does real well on gas for a two barrel Q-jet. Sent from my iPad using The H.A.M.B. mobile app