Or what is the purpose of high ratio rocker arms? Many people ask this question, "Why buy a cam and high ratio rockers arms?" Good question. For many applications they may not be cost effective and in many cases should not be used. They will usually be easier on all of the valve train. Practically every other auto, Chevy, Ford, Porsche 912, etc., manufactured in history has used high ratio rockers as standard items. When I was unable to achieve the performance from the cams that were available in the early VW days, I discovered that all high performance cams being sold for VW's were actually designed for 1.5:1 ratio rocker arms. In 1961 I took the 4 cylinder Porsche rocker arms and remade them to fit a VW with as much added ratio as I could. They turned out to be about 1.4:1. Now, even though many correctly designed 1.1:1 ratio cams have since been manufactured, we found many of the reasons and benefits Chevy, Ford, etc. gained by using a higher ratio which were very beneficial.
At first, we looked only at the race applications and have been using high ratio rockers for years. This was to get the lift needed to match the airflow that our modified heads are capable of delivering, especially in the 0.500" to 0.800" lift areas. It was simply impossible to have a 1.1:1 rocker arm cam ever work or have the valve train live at those ramp angles. So, the only way to have the engine live and work at the range the heads worked best at was with the high ratio rocker arms. With the use of proper ratio rocker arms we have now successfully been using up to 0.785" lift in our race car for years.
Many VW enthusiasts soon discovered these benefits of ratio rockers and are now using 0.475" to 0.525" lift in daily drivers and 0.550" to 0.625" valve lift in their all out street cars with great success.
The greatest benefit is that the high ratio rocker arm allows reducing the camshaft lift, ramp angle, and the acceleration rate at the camshaft and amount of side load over the distance the lifter must travel. This improves the tracking capabilities of the lifter and produces much smoother operation of the entire valve train. Lifter bore hole wear is reduced. The valve springs work less when the rocker arm weight is reduced at the valve spring end, one of the main reasons for moving the screw to the pushrod end. Also, the spring effectiveness is multiplied to the screw end of the rocker by the amount of added ratio in the rocker arm on the spring end, returning all the rest of the valve train much easier.
Most people agree that high ratio rocker arms give them more HP, much less noise, longer valve train and case life than a high lift cam using the stock 1.1:1 rockers. These benefits obviously make the higher ratio rocker arm set a wise investment. Another big plus is more valve lift without increasing the basic opening duration. This gives a much broader power range of all around usable HP. There is no loss of low end performance, which occurs with a long duration cam, which provides that much lift. If the same amount of lift is added at the cam, the lifter must be accelerated faster, then stop and return faster and has more side loading. This creates far more noise, wear, and requires much more spring tension to make the valve train track the cam. The wear and failure rate is much greater with a cam that has the lift added to it, rather than with the use of a set of high ratio rocker arms.
The Berg high lift rockers work superbly with the stock VW cam. They are an excellent bolt on item for improving the performance of your VW. Installing our GB 411-140 high ratio rockers with any of our carb sets, GB 903 or equivalent exhaust and GB 622 distributor really wakes up an otherwise stock VW!