Possible cause of an oil leak

[NeddyBear]

While under the Commodore repairing the exhaust system, I had a new U bend made up and I then welded up the entire 2.5'' piping to form one piece.
I noticed a small drip on the transmission drain plug and after further investigation I see on the rear right side of the block oil build up.
Block fittings wise I can't see anything that would be causing the leak and am now thinking with the help of the forum the cause might be the tappet cover seals which were last replaced 220,000 ks ago so I'm to degrease the entire block and gave it a water blasting using a short hand piece and am going to replace the right side seal and see if that stops the oil leak.
The example engine in the picture is of a 100,000 k engine that's going in our Austin project.
Wondering if anyone else has had an oil leak in this area and was the seals the cause.

 

[NeddyBear]

Well guys I jacked her up and gave the entire underside and block a good degreasing/scrubbing and gernied everything with a gun adaptor great for acessing those tight areas.
Added a new bottle of the Nulon engine stop leak that we've been using for 8 years and never a leak.
Next up will be to replace the tappet cover seals and then take her for a 600 k drive and see what the results are.

 

[Lex]

I thought l remember you replacing the rocker cover gaskets a couple of years ago?
Must be wrong?

 

[NeddyBear]

Time flies when were having fun and getting older, I remember Holden doing them before realizing I could do everything myself and yes I do remember buying a pair of the seals but couldn't find them.