| I had to make up a set of special lifters for this test since it isn't a running engine that can maintain oil within the lifters and cranking the cam around to open the valves would squeeze some of the oil out of the lifter, affecting the amount the valves are compressed and throwing the measurements off. So I machined these: 
You can see the two lifter bodies, one of them on the left has the dowel I machined to provide action on the valve stem. The one on the right has the dowel removed and it is sitting between the two lifter bodies. The bits at the top of the image are the OE parts for the lifters that were removed. I measured the lash of the lifter when the cam is installed, which came right out to 0.030". When I made the dowels, I machined them down using this spec and when the cams are installed there is just a small running clearance of a few thousandths between the lifter cap and the cam lobe to ensure I am getting full valve and spring action when the cam actuates them. And here is the video (and sorry for the low light, but the meat of it is all there): [ http://ashspecz.com/Image%20Gallery/VTC%20MOD/VTC-no-Over-rotate.mpeg ] I was surprised to find that it only took that little amount of torque to turn the cam - I'm so used to turning them by hand which is pretty tough to do, LOL. AS seen in the video, the cam torque will not overpower the VTC and allow the cam to over-rotate. Even when I tapped on the VTC housing, which is required in order to get the piston helix to snap loose from its grip on the gear teeth by way of the anti-lash mechanism, the cam did not rotate at all. The cam caps, lobes, and lifter bores were liberally lubricated with assembly lube for this test, and that stuff does really well in tests like this due to his really high viscosity. The VTC gear also has oil in it to keep its running surfaces lubed up and that is an unmodified VTC gear in the video. I might also take a video of the bench test showing what it takes to make the VTC over-rotate, and it is pretty ugly. YOu have to load it pretty good and then smack the VTC or the camshaft to get the piston helix's anti-lash mechanism to let go just enough to let the piston helix slide back and allow the cam to rotate. Without a shocking impact, it will not let go. It appears to me that the anti-lash mechanism also serves as a locking mechanism for the piston to prevent it from being driven by the cam on the closing event. Just after the video, for kicks I put a wrench on the cam at the cast-in hex to try and make it over-rotate, which it wouldn't do until I smacked the VTC housing. I understand that this is not a 100% conclusive test because the engine isn't actually running so take it for what it is worth. Brett is aware of the test I will be doing that will enable me to actually test this out on my engine to see if they are actually over-roating with the engine running. That will be the real acid test... But given the fact I am running the OE internal spring and my VTCs aren't rattling, I dont expect to find that the cam is over-rotating... If what I think I will find really is the case, this will pretty definitively show that 1) the piston isn't moving from cam drive and 2) the piston isn't the source of the noise. In your testing, Brett, did you do a running test like I've described?
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[ agpowers@bellsouth.net ] Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the tailor.
Albert Einstein
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