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1973 Mercury Comet -The Quest For 10s

A Mad Scientist Twisting Small Block Ford Dr. Setzer

Photography by John Baechtel, ,

The 2.02 intake valves, angle-milled heads, and not enough exhaust-valve-to-piston clearance necessitated cutting deeper 12cc valve reliefs in the SRP pistons. All this eventually created a 10.2:1 compression ratio that, with this incredibly tight quench and active chamber, works very well with California's miserable 91-octane premium pump gas. As Tom says, "It's never detonated-and I've tried."

CamologyAfter much counting of fingers and toes, Tom decided on a single-pattern Comp Cams hydraulic roller with 244 degrees of duration at 0.050 and 0.601 inch lift using 1.6:1 roller rockers. The idea was to save a couple of dollars by reusing the factory roller tappets. Tom also decided to test a set of the new Comp Cams beehive valvesprings that promised to control valve action at his high engine speeds by taking advantage of the springs' smaller, lighter retainers. The conical springs look spindly but offer as much or more overall pressure as an entry-level dual spring.

Electronic RamTo top all this off, Tom wanted something different for the induction system and began by fabricating his own using a Weiand small-block Windsor tunnel-ram as the base and then grafting his own aluminum sheetmetal lid using an Accufab oval throttle-body. The throttle-body exhibits a nose-down attitude that Tom was forced to include to clear the Comet's low stock hood line. Using homegrown fabrication, Tom adapted FAST EFI fuel rails and injector bungs into the manifold base, then used FAST 36 lb/hr injectors.

For his own edification concerning the carburetor versus EFI debate, Tom compared his homebuilt setup to a Victor Jr. manifold and a 750-cfm Mighty Demon carburetor and saw virtually no difference in peak horsepower between the two. The EFI's longer tunnel-ram runners did improve torque slightly over the carb'd intake's shorter runner length.

On the electron-swapping side of things, Tom added a FAST box not only for the luxury of finite changes to the fuel and spark curve, but also so he could integrate the basic Ford distributorless ignition to which he added eight separate MSD coils to deliver a solid ignition strike to each cylinder even at 7,200 rpm. An MSD Digital 4 Plus CD box was added mainly to employ its launch-rpm control once the engine found its way in the car.

Dyno DaysWith the final assembly completed, Tom entered what the boys at Westech call "The Polygraph Room" where he bolted the 306 to Westech's SF-901 dyno. The power quest began with a Victor Jr. intake and a 750-cfm Demon carburetor, but that was just to ensure the engine made acceptable power. Next, Tom bolted on his fabricated intake and eight-coil ignition with the FAST controller and set to tuning fuel and spark.

Once Tom had the engine fine-tuned, he uncovered some interesting personality traits. To no one's surprise, the engine was very peaky: utmost horsepower occurs at a stratospheric 7,100 while max torque hovers around 6,200. Not only that, but the engine clearly prefered larger 131/44-inch headers over the smaller, chassis-friendly 151/48-inch versions. The bigger headers made 10 more numbers everywhere in the curve, so it's a shame they won't fit in the car.

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