Hi all,
I've been using the original VIS kit for a little over 6 years now. To
address Bob's question about the BY-pass valve, this is what separates
this design from previous blowers. The by-pass valve is a vacuum
operated diaphragm connected by linkage ( on the earlier generation I &
II, the 3rd gen's are built into the SC body) to a door in between the
carb to blower & intake plenum. When vacuum is present at idle or normal
driving the door is in an open position, allowing air/fuel to circulate
round & round. It is sucked in just like a normally aspirated motor.
When you step into the peddle, vacuum drops in the manifold & the servo
return spring takes over & shuts the door allowing boost to build. This
happens seamlessly with no sudden bump, but a rapid build of torque. So
in theory , you could drive around all day and never see boost. I can
testify that this will never happen ;-) . The power & acceleration is
intoxicating as all of you know who have upgraded motors. My set up
uses an SU HD8 which is a great carb but has some issues in cold weather
driving (below 40 degs) . I don't know enough about the Holley Moss is
using but I'll bet it's been choked way down. The Eaton unit is self
lubricating & requires no oil feed line. I also like the serpentine belt
, much better than my V-belt .
As far as modifications go, it only makes sense to me if I'm putting in
more air/fuel I want it to purge it better. With 5-6lbs of boost the
stock manifold should do ok. A restricted exhaust might raise engine
temps too. I have used headers from day one so I can't give a comparison
on before & after. I am using Integrals SC cam which is similar to a GP1
with the overlap (113 deg)designed to contain the boost. The cam is also
installed with valve lift at 112 deg (slightly retarded, I think 110 is
stock) I have used the smaller pulley to raise boost to 9lbs. The SU
needle does ( UT) does make the motor a little rich, but it's my
insurance against denotation & piston ring damage. Am MSD with boost
control is also installed. I have done other basic engine changes to
enhance performance & keep things together but this applies to any
rebuild. Better ignition is critical.
Performance is certainly going to be better. The claim is 40-50%
increase in HP & torque. It's the torque numbers that are the most
impressive. The usable HP is also an improvement over conventional
methods. I still think that the SC is the best bang for the buck. Having
peak HP/torque at high rpm's is great for the track but in street fun or
autoX the power band is much wider & the torque is amazing. Although
these are not dragsters my last G-tech time was 14.5 1/4 mile & 5.5
0-60. Certainly not Ferrari stats but way better than stock. I would not
recommend this for extended road course use unless allot more internal
motor mod's were made.
To sum all this up , I'm a big fan of superchargers & would do it again
in a heartbeat.
--
Mitch Seff
Oceanside N.Y.
75 TR6SC
http://www.triumphowners.com/384
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