Hi:
I am a new member and have a 1986 560SL (140,000 miles); and looking for advice with diagnosing a valve problem. I think my problem may be either worn valve stem seals or valve stem guides. My problems/symptoms are:
- burns some oil, I get a puff of blue smoke when starting cold on cold days
- 3 of the plugs are fouling, presumably from oil leaking down the valve stems
- engine runs smooth with clean plugs
- recently failed the emissions test on high hydrocarbons

I am trying to confirm my suspected diagnosis and determine if its seals or worm valve stems. I understand I can replace the seals without removing the heads, but stem guides need the head to be removed. Obviously I would prefer not to remove the heads if possible. Is there a test (compression or leak test) that would help confirm which way to proceed? Also, a friend told me to replace the timing chain guides/tensioner while doing this. Is that recommended?

Any advice/suggestions would be appreciated.
thanks
Neil