could program them, allowed
speed equipment manufacturers to produce their own
parts. Instead of waiting for the next new casting from
GM, racers turned to specialists like Dart, Brodix,
Edelbrock and others to supply hardcore racing
components. It's now possible to build a complete
small-block or big-block Chevy V8 from a vast array of
aftermarket parts.
Racers have certainly benefited
from the work of aftermarket manufacturers because we
have access to reasonably priced parts that can
dramatically improve performance. When I put a
conventional Dart or Brodix big-block cylinder head
alongside the D-port castings that we used 20 years ago,
I am astounded by the differences. I would have loved to
have a pair of today's off-the-shelf heads on our Pro
Stock engine back in 1980 - we would have been
unbeatable! A second look reveals that the only
similarities between the factory and aftermarket
castings are the head bolt patterns - yet many racers
still regard these heads as "bolt-on" parts.
The downside to the aftermarket
revolution in racing components is that each
manufacturer concentrates on only one piece of the
puzzle. Every manufacturer strives to make better parts
than his competitors. In cylinder heads, for |
example, the ports get
taller, the valves grow longer, and the valve angles
become flatter. Since we are no longer working on a
"universal" Chevy engine, these changes ripple
through the entire engine assembly. Suddenly we need a
raised-runner intake manifold to match the ports, new
pushrods to complement the longer valve stems, and new
valve covers that will clear the shaft-mounted rockers
and large diameter valve springs that are necessary to
take advantage of the improved airflow.
The
proliferation of parts has produced pitfalls that can
trap even experienced engine builders. For example, the
length of the lifter bosses varies in both factory and
aftermarket blocks. Yes, you can drop a set of roller
lifters into a Gen VI big-block, but if the tie-bar
hasn't been raised to accommodate the block's taller
lifter bosses, the roller won't contact the camshaft's
base circle. If you set the valve lash with the tie-bar
resting on the top of the lifter boss, you get .200-inch
clearance instead of .020-inch clearance. And when you
fire up that engine, you're going to break valvetrain
parts instantly.
The trend in sportsman drag racing is
toward bigger and bigger engines. Big engines make big
power, but they can also cause big headaches because
everything has to fit inside a tighter package. You buy
a stroker crank from Company A, connecting rods from
Company B, and pistons |
