Grooved vs. Smooth
There is hope for improved
performance from the inversely mounted RKSport/Powerdyne supercharger. The blower comes with a smooth 3.12”
(6psi./lbs pulley) that spins off of the backside of the engines serpentine
belt. This is not the best way to do
things but it does work. This setup
suffers from slippage between the blower pulley and accessories belt. Many methods have been tried to reduce
slippage. One such method is to tighten
down the serpentine belt to such a degree that you may prematurely wear out the
bushings in your other accessories or using liberal amounts of belt dressing,
etc. Not the best choices. Others who have gone before have another
answer. They use aftermarket grooved
pulleys. The best known provider is www.ASPRacing.com You will not find the RKSport/Powerdyne pulleys on their website but
you can contact them and they will fix you up.
For example, ASP Racing sells a grooved (horizontal – cross cut) 3.12 @ 6psi or 2.9 @ 9 psi pulley (also 2.7 and 2.8 for 9-10 psi) for about $120. They even have 2.6” pulley. This is what the horizontal or cross cut 3.12 pulley from ASP racing looks like:
ASP cuts a 1/32 wide x 1/32 deep groove horizontally across the pulley face about every inch into the outer surface of the pulley..
Reports from users of these pulleys show they
dramatically reduce slippage and in turn improve performance of the
RKSport/Powerdyne L36 F-Body super charger system. When you combine a grooved pulley with the “John D
Power Wrap” performance
of the pulley system is even further enhanced.
Basically, when you upgrade to a grooved pulley such as shown above your
super charger will come closer to delivering (and sustaining) the actual PSI
rating based on the diameter of the main blower pulley as opposed to the stock
‘smooth pulley system’ of using a smaller pulley and allowing for slippage and
delivering an estimated or averaged PSI rating. This technique, however, gives erratic performance gains while
slippage is occurring.
It is possible that the
vertical or ‘spiral’ grooved pulleys can increase or accelerate belt wear. This is not completely conclusive but some
users have reported as such.
Having read so much about smooth pulley
slippage even with the improved belt wrap I went straight for a 6 psi grooved
pulley before ever running the stock smooth pulley. AWESOME!
Tips on changing out the pulley:
Remove blower unit from car. I used channel locks to hold the puller
inner hub and removed bolt with wrench.
You will probably need your pulley puller to finish the job of removing
the pulley. You don’t want to whack it
with a hammer or pry it off…can you say spindle-bearing damage? Oh, don’t lose the KEY.
Pre-heat the new pulley in an oven for 20
minutes at 250 degrees. This will cause
the pulley to expand a bit.
Using the stock KEY that came with the Powerdyne
start the new pulley on by hand. If it
does not slip all the way on the spindle to the base of the pulley hub you can
LIGHTLY tap the center hub with a rubber mallet. You can also use something like a 15/16” socket to center on the
pulley hub and then tap the pulley in place.
Once the pulley was positioned I again
used channel locks to hold the inner hub and a wrench to tighten the bolt.
BELT
SIZE: When and if you change to a smaller diameter
pulley such as the 2.9” - 2.7” you will most likely need a smaller serpentine
belt than the 105” belt that came with the original RKSport kit. A 103 – 103.5” belt should do the
trick. I have a Gatorback belt chart
right HERE. You can use the part numbers
at the parts store to cross reference a Dayco belt if you prefer that brand. The 103” Gatorback is #4061030 and the 103 ¾
is #4061037.