Build a Budget Race Car Part 3

In most parts of the country, when you flip the calendar page over to October, the "car" season is officially done. Race tracks close, cruise spots roll up their sidewalks, and all the nice cars go into hibernation. Conveniently, I moved from L.A. to Detroit three weeks into October. That meant my Camaro Mustang Challenge project was about to come to a screeching halt, at least in terms of time behind the wheel. But there's another big difference between gearhead life in California and the Midwest: The off-season gives you plenty of time to get to the work you never had time for during the good weather. And I have plenty to do.

Topping the list is building a new engine. After half a dozen track events, the original 5.0L in my '84 Mustang GT was hanging its tongue out, with oil pressure that started at about 40 psi and quickly dropped to under 20. Many times I'd glanced down at the gauge while running flat-out on a straightway to see it reading zero. But the tough little 302 just kept taking a licking. It wouldn't quit, even when the temperature gauge wrapped itself back around past 240 a few times, and that's after I installed a brand-new Fluidyne aluminum radiator and an oil cooler. But still, the writing was on the wall, so it was time for a rebuild.

Back in California, you can pretty much race and test year-round. Here in Michigan, the car goes inside, though my CMC Mustang sat on the back of an open trailer for almost three months getting rained on, snowed on, and frozen in ice until I finally moved into my new garage in Ann Arbor.

Building a CMC engine is pretty simple on paper, because the class rules regarding engine modifications are pretty strict. The letter of the law in the class is that everything must remain stock, with the exception of a few spec parts that can be replaced if you choose to run a carburetor, in which case you can upgrade the stock Holley/Motorcraft 4160-style four-barrel and aluminum intake manifold to a Holley 4776 600-cfm double-pumper and an Edelbrock PN 2121 Performer dual-plane intake. That's pretty much it, although there are some gray areas. The rules do allow for oversize rebuilds, and any flat-top replacement-style piston is OK, lightweight versions included. You're also allowed to update or backdate engine components within the allowable engine families. For Mustangs, that means heads, cams, and blocks from any '79-'04 Mustang are legal with the exception of Cobra engines as long as the engine meets the most important CMC engine rule of all: it cannot make more than 230 hp and 300 lb-ft of torque at the rear-wheels as measured on a NASA-approved chassis dyno. For every 1 hp or lb-ft over that limit, a 10-pound weight penalty is tacked onto the 3,150-pound minimum weight (for Mustangs; Camaros have a different weight) up to a maximum of 100 pounds over the minimum. After that, you're DQ'd. The horsepower/weight rule is meant to discourage racers from exceeding the class limits, because only a fool would take 10 hp at the cost of 100 extra pounds in a road race car unless he had no hope of making the minimum weight anyway. Considering that my Mustang weighs about 2,800 pounds dry and 3,000 with me in it, I already have plenty of room to spare. As it is, I'll need to add at least 150 pounds of ballast to make the minimum.

While plenty of CMC race cars run stock high-mileage original engines (at least until they blow up), don't let the low horsepower limit fool you into thinking they lead an easy life. The duty cycle of any road race engine is brutal in comparison to a street or mild drag racing engine, with lots of operating time spent either at wide-open throttle (WOT) or decelerating from high rpm followed by WOT acceleration. The constant cycling between high and low rpm puts a lot of stress on the engine's bearings and reciprocating assembly even at relatively low power levels. High oil temperatures from sustained high-rpm operation also take a toll.