1985 Mercury Capri - The Big Gulp

The factory carb sat on this 1-inch, four-hole spacer.

We bolted the Speed Demon in place of the factory carb.

Speed Demon carburetors measure between 575 and 850 cfm. They come with no choke installed, though one can be added. This version of the 575 has 1.280-inch venturis, twin squirters, and annular boosters.

The BG carb also has billet metering blocks and baseplate, and two 30cc pumps.

It was necessary to fabricate a new fuel line to accommodate the BG carb.

We connected our fuel line to the dual-feed line, which was supplied by BG (but does not come with the carb). After starting the engine and checking for leaks, we set the idle speed and ran a few tests. On the best run, we saw a gain of 4 hp, bringing the total to 220 at the wheels.

We then tried the Airflo from Professional Products. This unit is designed to smooth the airflow and help it turn down into the carb. Unfortunately, we saw no gain in power.

This is one item that may work in some applications and not in others, but for around $25 it was worth a shot. Note: We also tried the Airflo once more after swapping the manifold, and the results were the same. We're gonna try it again in our strip testing because, frankly, we're intrigued by the concept.

The stock manifold went bye-bye.

The aluminum stocker (right) will be replaced with the Weiand Stealth.

While both manifolds are of the dual-plane design, the Stealth is a high-rise, meaning the carb sits up higher, thus the plenum area is increased. The Stealth also has larger ports that allow the mixture to flow into the heads at a more advantageous angle.

Glenn Knell of Crazy Horse Racing bolted on the Weiand Stealth. When tightening a manifold, start from the center and work your way outward while going from side to side.