Hi,
I run solid lifters in my CA18det, and put them in only a couple of months ago.
See Page EN-73 of the R32 Workshop manual. Available online in PDF.or just the page at:
Shimming is a painful process. Mine were within 0.2 of a millimetre but I needed 7 different sized shims.. They are almost never all the same.
You use the tomei 2.3mm measuring shims, and then find out the clearances. All 16 need to be carefully measured with the 'measuring shims' in, then using two feeler gauges, measure the difference. "2.3mm + measured amount". You then add these numbers together, subtract the running clearance from that, and that's the thickness of shim you need to buy. The shims I needed for my head would have been special order from Tomei, so I went to Precision Shims. They cost AU$100-$200 to be custom made.
What you need, depends on whether you are running a CA20 head, or a CA18Ehead or a CA18de/t head.
Precision Shims are in Melbourne Australia. I am in Sydney after all. You could do the same. Chris is the fella's name, and they were 'spot on' after I gave him the measurements that I needed. If you tell him they are for a CA18, he should know what shape shim that you need. If you need more help, I can dig up my exact email request. You only need to supply the thickness and quantity of shims required. I had them in under 2 weeks.
http://www.precisionshims.com.au/
The shims should only need checking every 100,000kms. Sounds like your current shims weren't heat treated properly, the cam journals are wearing because of lack of oil, or the camshaft is wearing out for the same 'inadequate heat treating' or oil issue.
Regards,Chris