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Having trouble understanding valve lash with check springs installed and vtec locked

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I'm so lost in this p2v clearance checking situation. Ugh. So I've measured my p2v with check springs at 0.000 lash. The numbers were all low and that scared me. I made a post about it and was enlightened that because I have solid rockers the actual clearance that matters is the clearance at zero lash + the value of the running valve lash. This fixes my problem if that's correct.

So I thought I'd do a little experiment and set the lash on the check spring valves to the running lash and check clearances that way. The running lash is specified at .08. Well it was just bizarre as hardly an 1/8th of a turn of the adjustment screw from 0.000 lash brings me a lash where I can slide a .15 feeler through. Turn it back 1/8th of a turn to where it was and I can't fit any feeler through so it's back at 0.000. It might have even been less than 1/8 of a turn! I'm especially amazed and confused by this, normally a 1/8 of a turn is far less dramatic.

For kicks I depressed the valve with the checkspring when the .15 feeler fit through and my p2v clearance at the same crank position checked with zero lash was not .15 greater. It was more like .005 greater. So nothing adding up here.

Is it just that it's not really possible to lash valves besides zero lash with check springs installed and I'm wasting effort on this experiment? The valves are all the same fixed height as long as the springs are strong enough to hold them up. Other factors at play here are I've got vtec locked for the process and just visually I can tell/think that doing that seems to raise up the two adjacent locked in rocker arms to a higher level. Regardless of what level the rocker is sitting at lash is lash no? Also lash is typically measured between the cam base circle and rocker pad of the non-vtec lobes. For this experiment I've tried measuring it at the non-vtec lobes and vtec lobe since vtec is locked in. No difference.

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