The VAS Tool on a 964 Engine - A Sound Concept, but Still Has All the Flaws of the OEM Method
This time, we will study a valve adjustment tool called the VAS.
The VAS concept tries to take advantage of the 1.0 pitch thread of the valve adjustment screw. On the 964 (and 911) engines, the adjustment is 0.1 mm. With a 1.0 pitch thread, one 1/10 of a full 360 degree turn of the screw = a 0.1 mm axial movement of the valve adjustment screw. Thus, seating the adjustment screw against the tip of the valve stem below the rocker arm by tightening it creates a 0.00 mm gap (zero clearance) and then backing it off 36 degrees (1/10 of a full turn) creates a 0.1 mm gap. NOTE -- Be careful to never use a tool to achieve a zero gap because you may compress the valve spring and end up with a negative gap by pushing the valve open. Using fingers only is safe because fingers are too weak to compress the valve spring (unlike shown in the video below).
The problems with this method as shown in the video below are that (a) using the "pins" on the VAS to measure 36 degrees is a guessing game at best and holding that position -- especially on hard to reach valves is an impossibility; (b) the final tightening of the jam nut with the box end wrench moves the adjustment screw out of adjustment because the screw threads have not been preloaded (a screw is just a stiff spring) and doing it while holding the VAS steady is impossible; and (c) using the traditional feeler gauge to "check" the adjustment is meaningless and difficult. If you can slip the feeler in after the supposed 0.1 mm setting has been achieved using the VAS, the gap is too big. If you can't slip it in, it may be too tight. And finally, the entire process is cumbersome and not possible on some valves due to tight clearances with engine tin, engine compartment and the catalytic converter on some cars.
All of these problems are solved by SNAPGAP as shown in the short animation at https://snapgap.us/pages/how-and-why-snapgap-works
With SNAPGAP, each valve easily can be set accurately and mechanically in 2 or 3 minutes. No guesswork, no wondering.
If you are interested in learning more about valve adjustments from this Blog, please register on this site and you will receive notice of new postings and notice of our product release anticipated for May, 2019.
For an pretty good description of the VAS and a demonstration of the problems you can run into, please watch the video below.
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