This is exactly why I prefer not to mess with hydraulic tappets with hp engines. By zeroing your hydraulics, your basically trying to convert to mechanical lifters. Should have just gone with mechanical in the first place.
Here's the thing with zeroing hydraulics. You must be sure the engine is at 'operating temperature' when you do this. As the engine warms, the valvetrain clearance will open up. Expansion and contraction of the valvetrain components, along with the heads and block.
If you weren't quick at adjusting the valves on a fully warmed engine, you're going to end up with an amount of clearance on some of the rockers when things really warm up. When cold, you are still going to have a small amount of preload on the lifter. If you get on it with the valvetrain and engine not up to full temp, you may still get a small amount of lifting.
It's much easier dealing with having to adjust mechanicals every few months than playing around with hydraulics. By zeroing your hydraulics you're going to need to check valve adjustments just as regularly as you would have with mechanicals. Only it's much harder to get a definitive adjustment value with hydraulics (comparing values between hot and cold).
With mechanicals you can get the engine really hot and adjust the clearance on one cylinder real quick. Let the engine cool overnight and check that same cylinder at ambient temp and you will have a good cold adjustment figure to go by. Now you can run the valves at your leisure with a cold engine, not having to rush to make sure some cylinders don't cool down too much and give you differing adjustment values at a particular engine temp. Not sure how you could do that with hydraulics and have the same amount of accuracy.
I suppose you could zero lash everything on a stone cold engine, get it nice and hot and recheck the clearances to see how much growth you're getting on the valvetrain, but how would you translate that figure to a cold setting for a hydraulic?
Adjusting mechanical tappets also gives you the opportunity to inspect the upper valvetrain, check for broken springs, dampeners, and find out if any adjustments radically changed on you, which would be a very important clue to an excessively wearing valvetrain component.
With aluminum heads and block, you can have as much a .010" lash difference between engine hot and engine cold. Iron block won't be as much, but you are running aluminum heads.
It would be a good idea to get an in-car valve seat spring pressure checker to see if the valve springs have lost any pressure.
By the way, the engine looks HOT!!!
:biggrin: You need to add it to the hot engine bay pics thread!