Cornering and braking are common complaints on the AFB's
Another complaint is lack of a tunable secondary except for jetting. Edelbrock has just come out with the AVS improved line to counter that.
Much of the hard braking and cornering problems can be addressed with using the spring loaded "off road" 0.095" needles and seats. Unfortunately, from what I just tried last week on mine it doesn't look like you can combine the "high flow" 0.110" seats with the off road 0.095" needles, even though they appear to be the same size and appear to seal (the
seats are where the real difference is.) I am going to try it again soon, with more critically adjusted floats to counter the flooding I experienced.
You can overcarb with the AFB design much more than with the Holley design because the secondary is neither vacuum nor mechanical, but air flow driven. The secondaries, to a much larger degree on an AFB than on a Holley, will not open until enough air is pulling through them to demand it. There are limits to this though.
Those formulas are very conservative. With high flow big valves, 750CFM doesn't seem off the mark to me for a SBC. I seem to recall a recent
Car Craft or
Hot Rod Magazine article from some big dude with Barry Grant who also minimized the importance of the formula and recommended larger CFM.
I run Edlebrock or Carter AFB's on most of my "Fleet of Despair." On the Vette, which has a much weaker engine than yours, I have the 750 all manual with the choke wired open. It starts easily, usually without pumping even once, even in 25 degrees.
You won't hurt an AFB with abuse and backfires and such, but they are dirt sensitive. They are absurdly easy to tune and adjust and almost leak proof. Every normally adjustable thing on them can be changed with the carb on the car, holding gasoline, with no tools more sophisticated than a pair of needlenose pliers, a screwdriver, two torx bits, a drill bit and a small ruler.
They have always worked right out of the box for me, with no adjustments needed to get down the road.
Holley's offer the best tunability, but it is more difficult
to tune them and you have to take the carb off to do much of it. Additionally, an unimproved Holley can be rendered castrated with a single backfire due to damage to the Power Valve.
Barry Grant's Demon line is a line of very improved Holley's, just like Edelbrock's Performer is a line of slightly improved Carter AFB's. I had been going to try one soon to see how they work as so many like them. One responder here though hated them - he said they were plagued with flat spots and off idle stumbles that proved difficult to eradicate.
Not being much of a carb tuner, I still have these problems on my Edlebrock on my vette, but to a lesser and lesser degree as I learn what the hell I'm doing and pay close attention to vacuum, air/fuel gauge and spark plug condition.
Just as Edlebrock was not about to let the AFB sit alone, unimproved, for another 25 years while the "fuelie boys" rave on and on about their $1500-5000 fuel injection systems with 800 sensors and four laptops
Holley decided not to allow the Demon line to hijack the design.
The same responder who was highly critical of the performance of the Barry Grant line was positively silly about how good the new Holley Avenger series is. The Avengers are
Holley's "all fixes contained in the original package" offering and I've heard nothing but good things about them.
A last thing on the size issue: A little too little carb and your engine will just not put out the power it could, but will run smoothly and reliably. A little too much and under some circumstances it will run rough and waste gas, but will achieve the highest output at the highest RPM or under the heaviest load.
I will probably stay with Edelbrock's now, until I try forced induction on something, if only because I have 4 vehicles with them and all the tuning kits for them.
Good luck on whatever you pick.
