Why Flat Tappets?By now, our Engine Masters' competitors are digging deep into the rules of the build, developing a mental picture of what engine combination they can conjure to fit within the constraints, while still displaying power above all rivals. The rules serve as a guide, essentially defining the boundaries of the competition. One of the key changes this year is a move to a flat tappet cam limitation. With the growing popularity of rollers, some of you might wonder why. Initially, the rules of the challenge specified street-style cams, with no solid rollers allowed. In the last few years, we have allowed solid rollers, a change made to address cam failures experienced by some builders when pushing the abilities of a flat-tappet design over its limits. It might seem like the result was a good thing, since cam failures were predictably all but eliminated, but racers being racers, the rollers created other issues.
Building an engine for the Engine Masters Challenge is always a delicate balancing act, especially when considering the combination. With the rpm range set to begin at a rock-bottom 2,500 rpm, and the top of the test range at a moderate 6,500 rpm, the cam specifications are critical. Too much duration will certainly hurt the torque in the lower and mid-range of the dyno pull, taking the score down with it. Lift, on the other hand, can add power without the same penalty down low (as duration), and with very high-flowing heads, typical in the contest, the ideal cam would tend to have moderate duration and as much lift as possible.
By design, solid rollers are not limited by velocity (though the acceleration rates are), so the direction in Challenge engines has naturally been towards incredibly aggressive solid-roller lobe profiles. To make these lobes effective, the supporting ensemble of large custom-journal diameters, roller cam bearings, full-race or custom-made valvetrains, and comparatively high valvespring loads all began to make their way into our competitors' engines. Though cam failures became a thing of the past, valvetrain failures became a common point of attrition.
From the beginning, the Engine Masters Challenge was designed to showcase the ultimate in street engines. With extreme camshafts and 0.900-inch lifts, it seemed that engines were straying from that concept. While a lift rule would have brought the peak valve lift to whatever specification we deemed appropriate, the overall effect would be even less realistic than the previous unlimited format. A flat tappet is limited in peak velocity by the lifter design, and thus self-regulating for the purposes of the challenge. By going further and specifying regular production lifters and cam cores, the Challenge builders will have to work within the same constraints as any street engine builder. This year, it will be up to the builder's judgment-not the rules-as to how far a flat tappet can go
Snap-On: The Official Tools Of Engine MastersOur competitive engine builders are some of the most knowledgeable and capable engine experts you'll find anywhere. When it comes to tools, we knew a compromise on quality was out of the question. With so much on the line, tools have to perform; they can make the difference between getting the job done, and letting precious time slip away. For the second year running, Snap-On has stepped up by graciously sponsoring the tool requirements for the 2007 Engine Masters Challenge. Jumping into the Challenge requires confidence that the essential tools are up to the job, and Snap-On's reputation with engine professionals speaks for itself. Their tools give our participants the peace of mind that comes with knowing the tools they depend on will provide the performance they need, and more.