Another important point is that anytime you change master cylinder piston diameter, it will require changes to the brake proportioning valve. Let's assume for a moment you have discs in the front and drums in the rear and have just changed to a smaller master cylinder diameter. If the car is not equipped with an adjustable brake proportioning valve, this is a perfect time to add one. Do not rely on a factory proportioning valve to work if any modifications have been made to the car or brake system. As an example, just changing rear tire diameter will have a drastic impact on how much rear brake balance is necessary. A taller tire requires less brake pressure than a shorter tire. This is just one of dozens of examples of changes that can affect brake balance, which is why an adjustable proportioning valve is critical for modified cars. One point that many enthusiasts don't know is every adjustable prop valve has a minimum setting that allows a certain amount of brake pressure to pass through the valve. This means even when the valve is set at its lowest level, there will still be a given amount of pressure transferred to the rear brakes.
We spotted this AMC Hornet with junkyard-fresh writing on the window. Looks like it escaped cash for clunkers.
Pierce Peck, via CarCraft.com: It's time to take off the gloves and put together a shootout between the Edelbrock dual-quad Air-Gap combo (Glad) and the proposed Victor Jr./750 carb combo (Smith). It's fine to dyno both combinations, but why not go the extra step and drop it into a '65 to '69 Chevelle, optimize each combination (converter and gears), and run them down the quarter-mile, similar to the crate motor shootout published in the Oct. '08 HRM?
I realize the single-plane intake will likely make more horsepower, but I'm also t-hinking with that mild Comp cam (2-647-5) and relatively small heads, the dual-quad Air-Gap combo will have more than enough torque throughout the rpm range to show its taillights to the single-plane combination.
I am building a mild mechanical-roller-cammed, AFR 305cc-headed 496 for my '67 Chevelle and am intrigued by the fairground appeal of the dual-quad intake. This test would give me an idea of what (if anything) I may give up by going with this combo (in my case, Edelbrock PN 2066). Yes, I definitely plan on bracket-racing the car, and my build will be a slightly milder version (Comp 11-772-8 cam) of the one Smith built in the Mar. '07 edition of Car Craft.
Should I go with the dual-quad combo? And understanding that dual-plane-equipped big-blocks like lots of cfm, should I go with the 650-cfm Edelbrock Thunder Series AVS carbs or stick with the 500-cfm units? Let's duel this one out.
Jeff Smith: We'd love to duke 'em out, Pierce, but with the vast number of dyno tests we already have planned, we might get to it sometime in 2012. So let's see if we can shed a little light on all this. To bring everybody up to speed, Edelbrock makes two different twin four-barrel manifolds for the small- and big-block Chevys. The early-style manifolds (PN 5420 for the oval-port Rat motors and 5425 for the small-blocks) are similar to the dual-quad manifolds popular in the '60s. Edelbrock also makes a dual-four Air-Gap manifold for the Rat motor (7520 for oval-port and 7522 for rectangle-port) and small-blocks (7525). The Air-Gap manifolds will make more power than their earlier brethren while the early stuff delivers the nostalgic look that is popular right now. The PN 2066 system you reference is the entire package with an RPM Air-Gap dual-plane intake and a pair of 500-cfm Edelbrock carburetors.
Those are Wheel Vintiques Gasser Alloys on the front. Built one yet?