BACKGROUND
THE HISTORY of
traditional rocker arm geometry, for those who've used any philosophy of
design at all, was always based on two things: a SHOE TIP (scuff pad)
contact surface for depressing upon the valve, and a formula for roughly
measuring the rocker arm's length and pivot position which has been
known as the
1/3 RULE. Roller tip rocker arms
were not novel to Over-Head Valve (OHV) engines when they were first
applied to V8 automotive engines in the 1950's, having been used on
radial aircraft engines decades before. But roller tip rocker
arms DID make the
LEAP FROM the SHOE tip principles of design. THIS was
a mistake.
In 1958, the first roller tip
aluminum rocker arms were developed from an inaccurate method of design
that wasted rocker arm motion. (See:
History Of MID-LIFT.) It has been duplicated by every popular
rocker arm manufacturer ever since. It doesn't matter how big the name,
or how long they've been around, even the OEM manufacturers didn't
follow the now accepted (and demanded by some Detroit companies)
geometry called MID-LIFT.
The
History Of MID-LIFT
explains how an amiable, hard working, easy going Midwest machinist made
a simple mistake by taking an idea in his head to cut and paste
a roller to the end of a shoe tip rocker arm. But how do you explain
the insanity of bad geometry being used by racing's valve train industry
for so many years? The "roots" of most of racing's oldest and most
respected companies lies in men of racing passion, who got their hands
dirty; not in squeaky clean white lab suit engineers sitting at a
draft table holding a slide rule. The answer is underscored by examples
set in Detroit. There is no lack of accredited engineers at Chevrolet,
Chrysler or Ford. Yet, for cost reasons or just adhering to old school
thinking mistakes continued.
