[Contadino]

So I have the two dial indicators set up, 44 psi feeding into the Variocam, and everything seems ok except for one thing. I zero out both dials at <acronym title='top dead center'>TDC</acronym> and start rotating the crank. I expected the dial indicator on the lifter to pretty much stay at zero until the cam lobe starts pushing on it to open the valve. But that isn't what happens. The dial indicator actually turns the other way indicating that the lifter is raising up. It gets to about 0.018" before going back to zero and then as the cam lobe starts doing its thing, it starts moving down. I stop at 0.015", loosen the cam pulley and then move the crank to <acronym title='top dead center'>TDC</acronym>.

IF the valve is actually 100% closed when my dial indicator reads +0.018" then that means it is really 0.032" open when I do my adjustment.



Does this make sense to anyone? Or am I missing something?

Thanks for any advice!

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[Cloud9...68]

Could this be the infamous movement of the variocam piston due to leakage of air past its worn seal, causing the chain to move?

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[Contadino]

No it's not due to cam timing. I'm measuring the valve lifter directly.

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[Cloud9...68]

Hmmm... That is odd. My understanding of the problem with the WSM cam timing method is that on an old variocam (which all of ours are, unless you've sprung for a new variocam to the tune of $1300), the compressed air will leak by its seals, causing the chain to slacken. I could see how this could cause a "hitch" in the lifter movement as you rotate the engine. However, the fact that you're seeing movement of the dial indicator while the flat part of the cam lobe is in contact with the lifter doesn't quite fit the chain-slackening mechanism. I don't remember if this happened while I was timing my cams - maybe I wasn't paying close enough attention, but I don't remember it happening. Anyone else have this happen?

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[flash]

cloud - correct.



as for movement while on the flat, i'd be looking to see if the indicator is making contact somewhere else. getting those things in just the right spot so you can make a full revolution repeated times, all without the needle extension moving, is a real pain.



also, where the "flat" is, relative to the timing, can be deceiving. there definitely should be a few degrees of no movement though.

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