Need advice on gen 4 bbc oil bypass. Should I replace take out or cap? Pretty sure I am having issues with bypass. Motor starts at 70lbs cold idle. 40 lbs hot idle. After long pass goes to 20lbs. After idling around oil pressure comes back up to 40lbs. Have checked all mains rods everything all good. Any one have some.advise on this?

I'd say it's all working like it should. Your pressures sound pretty normal for an engine with clearances at mid spec or slightly above. So long as you've got 10psi at idle and over 30psi at 3000 rpm your in good shape. Mine runs pretty much the same as yours.

i had the same issue. i beat my head around trying to figure out something was wrong. thats been three years ago, motors still run perfectly, dont worry about it.

What is this bypass on a MK4 that you speak of? The bypass is a disc and spring in the oil filter adapter on a truck engine. When a remote filter adapter is installed on the block, that is removed.

I am also wondering what you are referring to as the bypass ??

The bypass only works when there is a differential pressure from the oil filter. It allows oil pressure to flow past the oil filter if the pressure differential is too large. reasons for this would be a oil filter that is plugged. If your oil pressure drops when the oil is hot and comes back up when it cools down, this is normal.