Does anyone here know the main differences between the performer and thunders series carbs from edelbrock. Looking to put dual 650's on my 401.
Performer = Carter AFB clone Thunder = Carter AVS clone. The AVS was based on the AFB, but included more adjustment to the secondary air valve.
I have a single carb intake but will eventually run dual 650's. Which carb would you guys recommend for my 401
Just remember, when you switch to the aftermarket AFB's or AVS's you're going to have to give up using your OE air cleaner. The necks on the later carbs are larger (the size of a Q-jet) and the OE breather won't fit with out welding in a new base with the later sized carb neck. Ed
A "good" single-four intake will make more power than a dual-four. It will cost less, and be less of a maintenence headache. There is NO reason to use dual-four carbs unless you already own 'em or you already have a dual-four car that needs to be put back to original. EXCELLENT answer. Then don't bother learning about the Carter clones. The AFB is a dead-end, the AVS is better but still not in the league of the Q-Jet. Buy Ruggles' Q-jet book, and a decent core carb or two, and either get a '66 manifold, or an adapter to allow a spread-bore carb on a square-bore intake.
Not many choices on an intake for a single carb. Maybe add a "Doc Dual plane"mod to a factory intake. And you want to go at least a 750 cfm Q-jet.
Or an 850 cfm Holley. Edelbrock carbs are pure junk in my opinion. A "doc dual plane" mod is where you cut the spacing out between the holes in the factory manifold. Do a search here on the board, I've seen it come up quite a bit. There are some detailed pictures and descriptions of what to do when you modify the intake.
I'd go with a single 4bbl intake, "doc dual plane'd", and a big ol' Holley. That's what I'm running, and I like it! Here's that pic of a doc dual plane intake again...
How 'bout a '66 manifold and a '76--'79 Q-jet that's been calibrated to your engine? The worst part of this deal (aside from paying for the manifold--I've been watching eBay for years in search of one at reasonable cost) is getting a suitable throttle lever on the Q-jet. The better your fabrication skills the better the outcome is likely to be. I don't really understand what is accomplished by grinding out the manifold's carb flange holes front-to-rear. Seems like a lot of trouble for minimal plenum volume gains. Partially knocking down the divider side-to-side would make for more impressive results. That way the two planes could cross-communicate; would make a big difference at higher RPM. Many other manifolds have this sort of thing designed-in.
Shurkey,,,, pal,,, dont cut the center divider down on your manifold ,,, it will hurt the bottom end something awfull..... Cutting out front to rear will make the manifold able to inhale a lot more air, all the way up and down the rpm scale.... the only restriction is the carb that you put on it.....and the air cleaner that is on the carb....
Connecting the primary and secondary on each side has a few effects: 1. adds a few inches of plenum volume (most 1 4 are too small) 2. flow leaving the rear of the primary and front of the secondary see less wall restriction There is also a 3rd, which is more work: the larger hole makes it far easier to radius the bottoms of the new entrances; 3/8" is enough. I also bias the flow slightly - less radius toward the divider than toward the ports. If you really need to run 2 Carter types, the AVS is easier to adjust since the secondary vacuum plates are spring loaded like a QJ. The AFB must be adjusted by adding or removing weight from the doors, and it's cut-n-try - there's no formula or diagram. My choice: mod the manifold and run a single QJ.
Depends on how much you cut out. It's entirely "tune-able" by starting small and progressively cutting more. It's repairable, too--just fill it back in with a piece of sheetmetal secured with screws/rivets/welding--whatever you feel comfortable with. I've seen manifolds with about a 1.5" by 1" section open between the two sides, and I've seen dual-plane manifolds with the ENTIRE dividing wall removed. Some present Edelbrock manifolds have the divider cut down about an inch for the entire length of the divider; but in the past they'd cast some of them with a smaller opening. The bigger the opening between the two planes, the more low-end you lose; and (in theory) the more top-end you gain--provided the runner size and shape is suitable for high-rpm use, of course. Can also allow use of a smaller carburetor, or higher-rpm with the present one. Adding a slot between the two planes is routinely done on other engine brands; and in fact I carved a channel into an Olds Toronado manifold with good result.
Edelbrock Oldsmobile O4B, showing out-of-the-box notch on plenum divider. Something this small is not going to "kill" low end torque!
