1979 FN help please

Reman Gen 4 454
79 fish natique
first couple of runs since engine install I noticed lifter tick on startup and then it goes away so I didn't run it hard went get it fixed.
Mechanic told me number 1 and number 3 lifters needed to be adjusted..
two weeks ago I run it and I noticed all the lifters start making noise when the engine oil gets to about 210 degrees . Brought it back to boat shop and they again readjusted all the valves

I was using straight 40
They had me switch to 20/40

so I go run it today as soon as the engine oil gets to 210 degrees the lifters start clattering

Oil pressure 25 idle 45 hot.. I also noticed that it runs a little bit different when the lifters are clattering.. if I put the boat in neutral and rev it up I hear a little bit of a pop or backfire..
if I continue to idle as soon as the temperature drops below 200 it quiets up again and runs perfect.. but if I get it back on step and get to 210 there it is again....

I'm lost . Hopefully the great Keno responds . Also a called my tech and he said timing may be too far advanced??

I'll have to find that out today .
Can timing too far advanced mimic or cause lifter like noise .. but runs perfect up to the point that oil gets up to temp , only after being on step

I think I might just sorta casually ask the technician what would happen if he went to zero lash plus 3/4 of a turn or even a full turn.  

Just to add a little extra .when oil is hot at 210 and lifters are clattering oil pressure is about 15 to 18 PSI at 500 RPMs. As soon as I raise the idol it's right up to 25 at 1, 000 and higher from there in the normal range.

Fuel pump push rod is in the block still ....

When lifters are flattering the exhaust sounds different almost a little muffled
Not a major difference, but different you can definitely feel something is not right..


Again it def sounds like lifters on both sides

I'm pretty sure base timing is set around 8°

Thank you Sir