[Silverback51]

I run dual 660's on my 460 and love them.

While I'm pretty good with Holleys, I finally had to take the car to a shop with a dyno to get them dialed in. The 660 is a race only carb with mechanical secondaries, 4 jet center squirters, and no power valve in the front metering block.

It took him about 5 hours to get them to work right. We ended up swapping out the front metering blocks for ones with power valves. He drilled up a couple passages also. Since the secondaries use metering plates, not metering blocks you cannot use jets and the selection of sizes for the metering plates did not match what we wanted, we installed Quick Fuel jetted metering plates so you can use jets.

Personally I prefer mechanical secondaries. I want my right foot to control the opening of the secondaries, not a vacuum diaphram and spring.