Yes the cleaning helped. Glad to hear it is running good!

today we re-adjusted the valve clearance at 0.14 hot (after our oil change last sunday) after we have put the valve cover and started the engine i was amazed at how the engine was much much more quieter and runs smooth too. test drive it and i immediately felt the responsiveness of the engine compared to before. and now both the rocker arms on # 1 cylinder has a lot of oil coming out.

i am certainly happy about this.
maybe it has something to do with us cleaning the rocker arm/shaft as well as the oil sump and pick up net.

i see..
next oil change i will try to use other brand.
we've been using castrol for a long time now, my dad's been using it for his diesel engine (passenger jeep) for almost eleven years now. but hes always on time for his oil changed.
me, i've been using it for five years ever since i got our datsun from my father in law.
and it's just lately that this problems arises.
let's just say it's a hand me down car. but i really love this pick up.

castrol oil sludges up engines for some reason (maybe the additives it has). this is why i don't use it. many years ago i done many engines failures (heaps)for a holden dealership that ran castrol oil in there servicing for new cars.they had castrol from new, eg; as little as 39,000km 3 oil changes by the book using castrol, engine locked up on bearings, when engine dismantled sump & pick up full of sludge and blocked up. was good for me, gave me work.

i remember now, before my last oil changed i went to this mechanic and told
him then engine is a little noisy then went inside and instantly poured something and as he's
pouring the substance into the engine i ask him what it was. he told me it was a diesel additive,
the smell awful and that was one month before my last oil changed.
could it be that it caused the sludge?

my last oil changed was November 30 last year.
am always using Castrol GTX 20w50.
we never used the datsun on long trips, just here in the city.
in the morning and evening only.

how often did you change oil before, what oil where you using before this problem.

yesterday we've finished our oil changed. turns out the oil pick up net on the oil sump is clogged.
we cleaned the rocker arm also. the oil was very thick, dark and dirty.
after we put it all back together, poured the oil and started the engine.
the engine runs smoother and the clanking sound was gone, just quieter than before.
but still less oil goes to the number 1 cylinder rocker arm intake and exhaust and we can hear a
little noise like metal to metal noise at times.
we did thoroughly clean the rocker arm/shaft.

i see.. i'm going to try the castrol magnatec 10w-40.
i'm gonna post a feedback after..

valvoline 20w/50 would be my next choice over penrite.