Thread: What happened to these valve/rocker arm shims?

Here is a picture of 4 of my 16 valve shims (well technically I have 8 shims and 8 guides, lol). These were the only ones that were worn down. Here's the kicker... the motor has 122 miles on it! Everything else looks bitchin and compression is perfect. Nothing else is bad in the motor. Any ideas on how this happened and how I can stay away from it happening again? Thinking of sending my cams out for WPC as well.

General Motor Specs that directly interface with shims:
S13 SR20DET
Tomei Solid Lifters
Tomei 260 Cams
WPC Treated Rocker Arms
Tomei/Nissan shims & Guides
Supertech Ti Spring Retainers
Supertech Dual Valve Springs

Complete motor specs can be found on 2_Liter_Turbo if you really want to know the rest.

The gap was set before the motor was ran. It was all within factory spec (.14mm-.17mm). There is oil getting to the shims just fine. The mating surface of the rocker arms and the tops of the valves all look good (a tad bit of discoloration on the surfaces where the really bad shim was).

"Chinese/eBay" shims?

How out of spec were they before removing them?

Looks like they actually cupped themselves around the top of the valve stems. Never seen that happen before. Like Ben said, maybe a cheap non oem shim that the metal quality was not soo great on. Ive yet to see any wear on any shims ive taken out.

Interesting

I wish it were that easy, lol. These are tomei/oem Nissan shims. The cupping happened on the rocker arm side, not the valve side. I might send them out for hardness testing and compare them to the hardness I got from old used shims (60 rockwell c scale), but used shims will always be harder due to the work hardening over the years. When i made my own shims a couple years ago, I was able to get up to 70 scale using O1 tool steel and heat treating, lol. The worst shim gap measured at .28mm I believe it was, lol

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If available you might want try to do a hardness test. I suspect that the ones that are cupped will be harder than the others. If so It might be possible that originally they were softer than the rest.

Lol, that's what I said a couple posts ago

I question the lashing method...

Lol, I'm pretty confident in my abilities to do no-brainer things like simple math and use a feeler gauge...