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Recently, to commemorate the millennium,
I began a series of articles posted on our web site, www.iskycams.com,
entitled “Tech Tips 2000.”
The first ten or so are under the heading
“Modern Myths of High Performance.” I decided
to write them because I didn't necessarily enjoy repeating
myself
over and over in order to undo the misinformation rampant
in our industry.
So, like “Tech Tips 2000,”
Cam Session is intended to set the record straight with
the truth, the whole truth and nothing but, so help me.
Ron Iskenderian: will be setting
the record straight in each issue of Drag Racing Online.
If you have any questions concerning cams or valvetrain
components or tech, just email camsession@racingnetsource.com
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Roller Lifters:
Keep 'Em Rolling Longer
Most racers are aware of the advantages of roller lifters.
For those who are not, a brief review is in order. Roller cams and lifters
are employed today in all-out racing engines where valve lift/area requirements
preclude the possibility of employing a flat tappet (solid lifter cam).
Higher lift requires higher valve spring loads (pressures) and flat
tappet cams can only handle so much. Additionally, increased rates of
lift (cam lobe velocity) above .007" per degree for example on an .842"
diameter G.M. lifter, would cause the lobe to reach-out over the edge
of the lifter's cam face. Consequently, with either too much spring
or too high a lift rate, most racers know that extremely radical flat
tappet cams will eventually self-destruct.
But, what about roller lifters? Are they as indestructible
as many believe? How do we prolong the life of their roller bearings
in today's modern race engines? Roller lifters require special care
and maintenance if they are to provide good service life. Here are the
3 most important factors you should consider to insure their success.
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1. AVOID DRY "START UP": Roller lifter bearings are assembled
with a "tacky" rust-preventing grease that is not intended for lubrication.
Therefore, new lifters should have their roller bearings thoroughly
washed in clean solvent or acetone to completely remove this assembly
grease. After air drying, premium motor-oil (non-synthetic) such
as Kendal GT-1 should be used to pre-lube the bearings just before
installation.
2. AVOID "OVERLOAD": Increased load always
means reduced service life. Want 50% more thrust from a jet engine?
Ask Rolls-Royce or G.E. and they'll tell you to expect about one-fourth
the service life between overhauls. Similarly, employing drag race
valve springs in the 800, 900 to 1000 lb. range will reduce the life
of your roller bearings between rebuilds much the same as will employing
high-impact roller cam profiles.
3. EMPLOY A REV KIT : The primary advantage
of Camfather Ed Isky's invention of the 1950's is that by pre-loading
each roller lifter bearing to its respective cam lobe, you eliminate
needle roller bearing "skew". Skewing (the momentary mis-alignment
of the bearings' needle rollers to their respective races) is provoked
by the start-stop skidding action of the roller bearings each time
the lash is taken-up. Eliminate it and you extend roller bearing life
dramatically! Unfortunately, many engines such as the big block Chevy
which could use one the most, don't lend themselves to such an installation
because of the severe angularity of the pushrod coming out of the
lifter.
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