Last month, we put together our 402's short-block with forged internals from Lunati and Wiseco, and went over how to set up bearing clearances, ring gaps, and other essentials for assembling an engine that will hold up under the rigors of a heavy right foot. This month, we'll put together our top end, and go over a process that has become hotly debated in recent years: breaking in a flat tappet cam.
More than a few readers are probably wondering why we went with a flat tappet cam in the first place. Why not a "modern" roller valvetrain that will make gobs of power? Well, first, roller cams aren't exactly modern. Most people don't realize that roller cams in engines go back to the early part of the 20th century, and are just as old as flat tappet cams. The first aftermarket roller tappets came out in the ‘50s, designed by Bruce Crower. By the ‘60s, most of the performance valvetrain companies had roller cams and lifters in their product lines for use in racing and hardcore street applications. But these were expensive, and flat tappets still ruled the world.
It wasn't until the late-'80s when roller cams became standard from the factory that their affordability in the aftermarket started to increase, and almost 30 years later roller cams are as common as flat tappets, but they still haven't been able to depose them as top dog, sales-wise. The reason still comes down to cost. When going to a roller cam, you're typically looking at an increase in cost of build between $1,500 to $2,000. That includes the cam, lifters, pushrods, valvesprings, retainers and locks, and cam button spacer. For the engine builder on a budget, that is a hefty price increase.
Flat tappet cams still offer great power, but on a more budget friendly level. And for racers who compete in classes where rules specify them, flat tappets are the only option. So, in sticking with our theme of a real world, budget-friendly big-block build, we chose a flat tappet cam. Specifically, we went with a mechanical/solid lifter cam, for that old school feel.
The main issue with flat tappet cams today is their break-in procedure. Twenty years ago this wasn't a problem. But the EPA tightened standards on motor oil and forced companies to remove most of the heavy metals that were in the oil, so breaking in flat tappet cams became problematic. Zinc and other ingredients in oil were having a negative effect on certain factory emissions control equipment. These metals were critical for initial flat tappet break-in. Without them, the break-in procedure wouldn't go properly, and you'd end up with a cam lobe (or several) wiped out.
Thanks to the performance lubricant companies, this is no longer a problem. Special "heavy metal" oils are now readily available from Comp Cams, AMSOIL, and others that help ensure cam break-in goes smoothly …as long as the break-in procedures are followed.