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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.

---0---- --0----- -0------

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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