When rebuilding and upgrading my stock 500EFI to a 800hp whippled 509 2 years ago, the only parts I reused were the block, crank and 8qt oil pan. I upgraded the entire oil system to the Melling 10778C oil pump, -12 lines, AN fittings, and one of the largest Teague oil coolers rated for up to 1400hp. When oil temp is under 120 degrees the motor always has 70-80psi of oil pressure at idle, warm oil temp is ranges from 70-85+psi at 2000-6000rpms. Even when oil temperature gets up to 250 degrees in the pan it still maintains 65-75psi running WOT at 6000rpms. I have installed an oil temp sensor before and after the cooler to verify temps, and have found the oil cooler lowers oil temp by about 70 degrees. So if the engine oil is showing 250 degrees in the pan, I am seeing 180 degree oil temp going back in the motor, after the cooler. Most of the time, hot oil pressure at idle is 30-40psi when oil temp is above 200 degrees in the pan. I am running a mechanical Auto Meter oil pressure gauge and to me, this pump has been operating and performing as it should.

This past weekend we were running hard between 80-105mph at 4500-6000rpms for 30+ miles, with air temps being 110-115 degrees and water temp around 85-90. After running in these conditions, the oil temp was 240-250 degrees in the pan and I noticed it only had 12-20psi at idle, which was a little unsettling. If I bumped the idle up to 1500rpm, oil pressure went up to 35-45psi instantly and returned back to normal pressure after idling for 5-10 min. The motor only has 65 hours on it since I built it, about 15-20 hours since the last oil change, and I've always ran Kendall 20w-50 and Wix 51222 filters.

Melling states the 10778C pump may produce low oil pressure at idle since it has anti-cavitation grooves, which I was aware of when assembling the motor. With the elevated water and air temps being so high this past weekend, maybe it is what it is, and should not hurt anything. I now find myself wondering if there is a windage issue; could the oil have been aerated and needs a bigger pan with more capacity? The pan might only hold 8 quarts but when priming the entire system initially, it takes almost 12 quarts to fill the filter, cooler and all the lines in between. Would a straight 50 weight oil be better for these conditions? Maybe I am over-thinking this, since it is still above the oil pressure standard of 10psi per 1000rpm. But it just doesn't sit well with me when this motor typically has plenty of oil pressure. I am now also contemplating pulling the motor to swap oil pumps, to the Melling 10778 without the anti-cavitation feature, in hopes of solving the low oil pressure condition at hot idle. I am now loosing sleep over this and any educated advise would be much appreciated.

had basically this same issue. dont worry about it. mines been running great for four years now.

that is why i don,t use the 10778c in a marine engine,i have installed many 10778 pumps and the pressure does not fall after long hard runs,i would not loose any sleep over it,you will be fine.

Should be fine me personally i like a 10 qt pan ,sounds like u got the rest coved ..

Exactly. I ran that pump in a 548 and had same issue, I won't ever use it again.

That’s a trait of the 10778c pump. It will be fine. Doesn’t need much pressure at idle, still has decent volume. I dont use the c version for that reason

When I built this motor in 2019, I had originally planned on using a M-77HV pump which has always worked well for me in the past. Teague recommend the 10778C pump and claimed they have not experienced any problems with low oil pressure at idle from the anti-cavitation feature. So I purchased the entire oil system from TCM, minus the oil pan. Of course now when I asked Teague about this, they stated that they do not run the "C" pump anymore because of low oil pressure at idle... Since I cannot leave anything alone, I'll probably swap to the 10778 pump at the end of the season in hopes of resolving this issue. Thanks for the responses and reassurance.

Ive run several 20-50 products, Kendall, Lucas and Mobil 1. My idle oil pressure almost always dropped after 20-25 hours. Do an oil change and run Amsoil Racing 60wt. Or whatever your favorite is... See what your idle oil pressure is - its only an oil change. For me, the Amsoil 60wt ran cooler and sustained higher idle oil pressure for me, sometimes twice as long.

i tried different oils and weights, nothing made a difference. even put pop off valves on my valve spring oilers thinking they bled off too much oil. ive had my oil tested three times, every time it came back normal. now i dont worry about it, ive got 70psi at 5400.

Your over thinking it. Your only measuring your oil temps. What you not taking into consideration is the block component temps after those long runs. Just as the oil gets a lot hotter so does everything else not in direct contact with a water cooled surface. Clearances open up during those long hard runs right along with the oil getting hotter. You've still got plenty of oil pressure at idle. You've still got more than plenty of oil pressure once you bump it off idle. Add to it you've done oil analysis multiple times and nothing found in it proves you've done no damage and have no real issue other than seeing an entirely new to you condition. Go run the balls off it and have fun.
And not running an anti cavitation pump just because of idle pressure makes no sense. That pump saves your motor at high rpm where it's needed. They'll live at idle on next to nothing.