Date: Sun, 3 Jun 2001 12:38:31 EDT
Reply-To: Wolfvan88@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Lilley <Wolfvan88@AOL.COM>
Subject: Re: WBX Mods Graph
Content-Type: multipart/alternative;
Larry,
Here is a copy of the post I made earlier.
Stock rockers are 1.1. What the ratio means is that for every X amount of
cam lift, the valve opens further by 1.1/1.25/1.3/1.4 inches. Using ratio
rockers is a way for the valve to be opened further than the actual cam lift
to keep the wear on the cam and lifters minimized. The cam does not have to
go to extreme angles against the lifter to achieve the same total lift.
The ratio is achieved by moving the center pivot line further to one side.
The longer one side is the greater the ratio.
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One other plus for using ratio rockers is that the arc that the adjusting
screw takes is reduced and that reduces the side load on the valve stem,
increasing the valve guide life. When you use swivel adjusting screws or
roller tip rockers the side load on the valve stem is further reduced,
further increasing the valve guide life.
Boston Bob states that the 2.1L tends to eat guides, by simply utilizing
swivel adjusting screws on stock 1.1 ratio rockers (You will have to use
aftermarket Rhino 1.1 ratio rockers with a 9 mm adjusting screw) you can
dramatically increase the valve guide life.
**attached is a picture that shows the rocker arm shaft off center compared
to a stock (1.3 ratio)
________________________________________________
<<<The ratio rockers in on these dyno reports are 1.4. The Pawter rockersare
1.3, and I believe the original rockers that Robert Lilly had usedwere 1.25,
and then switched to 1.3. which I guess you have.>>>
I have a modified cam that has an increased lift from stock. I choose the
1.25 and 1.3 because the total lift is more than the 1.4 rockers on the stock
cam.
I used the 1.25 at first. These were the VW Rhino 1.25 with the 9 mm
adjusting screw. I used the Rhino swivel adjusting screws. They have the
entire head that swivels to reduce valve stem side load. Used with solid
rocker shafts, they are an inexpensive upgrade and are mild.
I then switch to the Pauter 1.3 roller tip rockers. I wanted the roller tip
to further reduce stem side loading (even though the arc is reduced the Berg
rockers DO NOT reduce the stem side load as much because they still slide on
the valve tip during the lifting motion) The 1.25 were discontinued from
Pauter that is why I went to the 1.3.
IF you DO NOT change the cam use either the 1.3 or 1.4. IF you ever plan to
change the cam use the 1.3 to avoid changing in the future otherwise use of
the 1.4 is fine.
stock cam I: .330 with 1.3: 0.429 with 1.4: .462
E: .317 with 1.3 0.412 with 1.4: .444
#91 WebCam I: .363 with 1.3: .472 with the 1.4: 0.508
E: .363 with 1.3: .472 with the 1.4: 0.508
Looking at the above chart, the use of the WebCam cam AND the 1.3 ratio
rockers, you get a greater lift than with the stock cam and the 1.4 ratio.
I chose ratio rockers because they offer increased air flow, maintain air
speed through the intake ports at lower speeds and improve the bottom end
because the valves are opening faster than stock valves and accelerate the
air flow.
Another key is, with the WebCam, the exhaust is open greater and longer
allowing for more exhaust to exit along with the increased duration to get
the fuel mixture into the cylinder sooner from increased exhaust scavenging
to give each charge more power. Added to the cam benefit is the coatings
that keep the exhaust hotter as it exits to keep a higher exhaust gas speed
that increases scavenging. This is why, in my set up, the stock exhaust pipes
work better. Plus the stock pipes are patterned after 914 race exhausts...4
to 2 to 1.
Rockers increase airflow without expensive port work. Sometimes with
porting, you lose low power because the air flow decreases in larger ports
due to reduced air speed (physics) the way to overcome this is a higher rpm
to pick the speed up. The length of the total intake also affects air speed.
Ratio rockers do not decrease low end power but increase it. The valves are
opening sooner, opening further and held open longer but air speed is
maintained because the port size has not changed, thus allowing for more
air/fuel to enter the chamber, producing more power. The effect will be
enhanced when you also modify other systems to flow more air. Better
muffler, air filter, match porting, cleaning up ports of restrictions. All
small changes add up to a big change overall.
If you put on rockers add exhaust wrap to keep the exhaust gasses hot to pull
more from the intake into the cylinders, change the air filter, change to
triple or quad plugs to burn the gasses better to get more power, then you
will need to use less pedal to get to the same speed and use less gas because
you are getting more power from the same amount of fuel. When you make
changes to one area, see how it changes other areas to keep it balanced...
Robert
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