There are two types of Rollers available...
those that run needle bearings at the shaft and those that run bushed, the
former being more expensive.
They come in a "true" 1.3 ratio (Dr. Marty
out on Long Island) and hi-lift 1.5's.
They do two things in 1.3 ratio and a third
thing in hi-lift 1.5 ratio.
1. reduce side loads on the valves and thus,
prolong valve guide service life.
2. reduced operating friction (needle bearing types mainly) and thus, absorb a
mite less HP.
3. more effective cylinder filling over time at any given valve lift,
especially when the flow really gets going and most especially
so with hairier cams at higher rpm's.
But see Vizard's chapter on this 'cause it doesn't always work this way with
all cams.
With a stock cam, the difference will not be
in improved high end HP as would be expected with a hairier cam and most
especially when matched to larger intake
valves (with ported head with improved intake manifold or induction set-up to
match), but more in increased mid-range torque in consideration of stock cam
profile.
In my Cooper "S" spec. 1293 running 4
degrees advanced for low/low-midrange
street torque ("stoplite to stoplite" application) there is a helluva torque
difference between running a 1.3 ratio and 1.5 ratio. We tried them both. You
don't even have to put it on the dyno.....it is that obvious in "pulling" power.
And I preferred the more quiet Mini
Mania upgraded stock (but pedestal design
improved) "true" 1.3 set-up I purchased to
take the place of the way noisier 1.5 bushed
roller set-up I had previously.
(Still got the MiniMania 1.3 set-up if anyone
interested. Less than 200 miles on it. $175
new so I guess $100+ shipping is MOST
reasonable:).
Cap'n. Bob '60 :{)
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