Carb Selection?????

I have a 360 in my 68 Barracuda. It's 10.6:1 compression, XE268 cam, dual plane, headers.

I have had a Holley 600, Holley 670, Demon 725 and Holley 750 on it. The only 1/4 mile times I have on the car are with the 600 and have a best of 13.7 @ 102 with amiserable 2.2 60' time.

By the butt dyno you can feel a definate advantage to the 725 and 750 over 4500 rpm but below that the throttle reponse of the 600 made the car much more enjoyable to drive. The Demon 725 was especially bad below 2000 rpm and BG's tech line was useless.

I recently picked up a Street Avenger 670, this has to be the closest thing I have ever come across to a drop on and go carb. Tweaked the choke and played around with the secondary springs but have never had the bowls off. Anyway, the but dyno can't feel any difference on the top end compared to the 725 or 750 and the low end throttle reponse is as good as the 600. Plus, it gets 5 mpg more than the 750 and 2.5 more than the 600.

I don't know if all the Street Avengers are made this way but the unique thing is the primary venturi's are smaller than the secondaries even though the have the same size throttle blades. The smaller venturi is likely why the low rpm throttle response is so good.