smoke puffs, dirty spark plugs and detonation

["Trenta Ltd" <Trenta@domain.elided>]

The problem is following:

1) When changing spark plugs on my 164 3,0' 1990 I noticed that the plugs
from cylinders # 4; 5 and 6 are "dirty"
2) On medium to high revs I see a smoke puff behind me.
3) When the engine is warm there is a rather strong detonation when
accelerating (due to the dirty plugs?)

Just changed the oil (BP semisyntetic) and after driving ~350 km I don't see
any oil level changes and it is still clear like from a can (recently had to
change the oil pan). I heard an opinion that if the rings are weared the oil
should become dark pretty fast.

So, the questions are:

1) How can I check what has to be replaced (seals or rings or :-( smth else
too )

2) Is it reasonable to change the seals, etc only for the upmentioned head?
The other 3 plugs were perfect.

3) Is there any chemical treatment known that could help for a while?

4) What is the parts cost in Europe and where to order?

Thanks in advance

Janis

P.S.
In exchange to this information I can offer a nice receipt how to keep the
engine clean. I tried it myself.
You have to find a nice speed bump or something similar. Larger stone (my
case) on the road can suit your needs. If you don't know any such place to
go and are lazy to drive around looking for it, you can ask your friend
(supposing you will not like to do it yourself) to help with a hammer.
The aim is to get a medium sized crack in the oil pan. After it is done you
have to drive your car daily for about 1 - 2 weeks checking oil level twice
a day and adding oil when needed. I had to add ~ 0,5 liters daily. After a
couple weeks you have to replace or fix the oil pan, put in a new oil and
you can be sure the engine is perfectly clean. I have done it twice, first
time only for 3 days, but now changed the front springs to stock ones to
avoid the 3rd.

------------------------------

End of alfa-digest V7 #976
**************************