[DeTomaso] Roller Rocker Arms
JDeRyke at aol.com
JDeRyke at aol.com
Sat Jun 25 01:19:28 EDT 2011
Use aluminum full-rollers for street engines with reasonable valve spring
pressures, and cast-steel or even forged steel on engines with locomotive
springs. The alloy used is not weldable nore hreat-treatable= kinda like piston
alloys. The main effect is a cooler running engine from less friction in
the rocker system, not necessarily more power. One article mentioned 15F
degrees less oil temp in a high horse engine with full roller rockers.
As Chance said, Harland Sharp arguably built the first aluminum roller
rockers, and I got my set- used -from a road-racer some 15 years ago. Still
running just fine. Nowadays, there are off-shore shops that have a machine that
extrudes a 6 foot long rockerarm-shaped bar, which is then sawed up and
machined to make aluminum full-roller rockers all at very low cost. And low
strength, too.... beware of really low cost assemblies.
The rollers that run against the valve stems in all these assemblies are
just hardened steel running on a hardened steel axle, lubed by splash; look
for a rocker in which the 'axle' is removeable with a c-clip or something so
the roller can be replaced. Cheaper assemblies use a staked rivet or other
non-removeable shaft. The rollers do occasionally flat-spot from valve float
or lack of oil up on top, and if you can rebuild the assembly, that's worth a
little extra. Otherwise, a flat spot junks the rocker. FWIW- J DeRyke
More information about the DeTomaso
mailing list