Measuring shim clearance with feeler guage question!

[-Nemesis-]

A quick question for the mechanics:

I'm doing the shims on my 1uzfe on the passenger side bank as one is very noisy. I'm measuring clearance with a feeler gauge. The question is:

How hard do i force the feeler gauges in between the lobe and shim to check clearance?

You can't attack the shim from directly side on with a feeler gauage, you have to come down at a bit of an angle because of limited room. I noticed that I could get the feeler gauge in where it fits snug. But if I add up to another .1mm on some of them, if I press the feeler guage in hardish, it will still all of a sudden slide in between the lobe and the shim, once flat i can move it back and forth. What i'm wondering is if by pressing fairly hard on the guage, will it actually be slightly depressing the shim/bucket and give a false reading? Should I just get the feeler guage snug between the surfaces, or get it so I can't quiet force it in?

Any tips? (I've already got the suspect ones out and measured, i'm just paranoid now about whether I under-measured the tolerances....

 

[-Nemesis-]

For example:

On the main suspect shim I found that I could get the feeler gauges in the gap set at .35mm with only moderate force. Once the feeler guage was in the gap they move around quite freely.

However on the same shim I found that even up to .49mm worth of guage I could still get it to slide between the shim and lobe using considerable force to get it in there initially. Once it was in there I could move it back and forth but feel it was getting a decent amount of pressure (drag) from the shim and lobe surfaces.

 

[rms]

Clearance for inlet is .15 - .25 mm. Set a 'go' feeler at the clearance you are aiming for with a slight amount of drag, and a 'no go' feeler at .05mm larger.

Why have the clearances increased ?

Is the aluminium bucket (follower) collapsing under the shim ?

The reason early UZ's spit shims when using high rpm or aftermarket cams/springs is the aluminium bucket collapsing and allowing the shim to rock.

 

[-Nemesis-]

That's what i'm unsure of, the higher clearance I mentioned (0.49mm) was me forcing the feeler gauge in there. So I wasn't sure if it was going in because it's actually depressing the shim/bucket.

I think i'm going to gauge it off the snugly fit clearance, which was .35mm exactly. Which means it's out by .15 and no doubt was the cause of the really annoying tick in the back corner of the head!

Incidently, two of the four shims I pulled out to replace are the exact thickness required of an alternate two of the four being replaced. If that makes sense hehehe.

 

[Lextreme II]

Perhaps this article would help http://www.lextreme.com/valve_clearance.html

 

[-Nemesis-]

Woohooo no more tick tick tick...

Big thanks to Rod (Zuffen) for the loan of his shim tools!