If six rockers are getting oil, there is no problem with the block-to-rocker shaft oil feed.

Since only two valves are not getting oil, disassemble the rocker shaft assembly to find the problem:
1. Set the engine to TDC, and check that it's on #1 valves are loose (have clearance)
2. Loosen all eight rockers
3. Unbolt the shaft assembly

i see. thank you so much for your inputs. i deeply appreciate it.
now i know the right procedure and how to clean the rocker shaft assembly.

right now the engines really noisy even when driving it 35minutes to work under the hot sun.

i'm really glad i joined this club because here in the Philippines there is no clubs or groups like this.
even the parts here are very rare, the guy at the auto supply told me that i have to wait one week
before i can get the distributor rotor and rotor cap cause they don't have it on stock.

anyway, sir would you recommend the castrol magnatec 10w 40 for the a12?
before i'm using castrol gtx 20w 50.

thank you so much!

I recommend natural oil, rather than synthetic. But synthetic oil works too. 10W-40, 10W-30 or 20W-50 is good. The most important factor is to change it regularly.

Here is official Nissan recommendation by temperature:

thank you so much... :)

penrite HPR-30 is what i'd use ; cheers

cant get that penrite in malaysia :(

yes the key is to change the oil regularly.

sadly, no penrite oil here in the philippines..

what other brands do you have.

Mobil 1 Fully Synthetic 5w-50
Mobil 1 Super Synthetic 15w-50
Castrol GTX Mineral 20w-50
Castrol Magnatec 10w-40
Shell Helix 5w-40
Shell helix Super Mineral 20w-50
Caltex Havoline Fully Synthetic 5w-40
Caltex Havoline Energy Synthetic 5w-30
Caltex Havoline Formula 20w-50
Citgo Supergard Mineral 10w-30, 10w-40, 20w-50
Petron Ultron Touring Mineral 20w-50
Valvoline Dura Blend 10w-40

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