New iron 408 with 2.5k miles on it with a ported ls6 pump, started noticing lower oil pressure. Dash gauge never reads above 35 so I installed a mechanical gauge. When warm it will read 25 psi and almost 50psi at 4k rpms. After i beat on it, pressure is 20psi idle and 40-45 wot. The oil has not quite reached the mechanical gauge yet, maybe 6-12in left in the line before it will reach the gauge. How accurate are the mechanical gauges if the oil is not physically in the gauge? Bearing clearances are .0025 and have tried 10w-30 conventional and now have 10w-40 Valvoline synblend. I have done countless hours of searching and I am familiar with all the issues that could be causing this, I was hoping someone with similar symptoms might have an idea before I start to tear it apart. TIA.

 

Hello , I would guess that the oil needs to be all the way to the gauge to be accurate . That's something I was wondering about myself was if I should fill the little tube when I install my mechanical oil gauge ? Maybe somebody with first hand knowledge will chime in . Good luck

 

TTT for the night...

 

Anyone have experience with improper or no oil "barbel" plug in the back of the block? I wonder if the machinist left it out, but I would suspect much lower oil pressure if that wasn't in there.

 

The oil does not need to bee up to the gauge. The air in the line will compress to whatever the pressure the oil is at and give you the same reading.