Dyno’d my hemi the other day and noticed a slight drop on pressure at higher rpm. Wanted to get some thoughts.

4.5” stroke
Charlie’s oil pan (10qts)
Single line with milodon pump
Crank scrapper and windage tray
Added returns to the oil drain backs to get them below crank

Time for a dual line? I ran the pan and pump previously with a 4.15 crank and use to shift at 7k. I never dyno’d it or paid that close attention to what the oil pressure did during a run. That motor ran for years and bearings always looked great.

If it’s still on the dyno take a quart out and see what happens.

I run pretty much the same stuff except wedge heads. Charlies pan, Johnson scraper and screen, Indy cover on Melling HV pump, single line. All Als stuff is single line as well. Not sure if the Milodon cover is better or worse than the Indy? Did you have 10 in the pan? Or 10 in the entire motor? The factory dipstick location didn't work. The stick hit the pan above the oil level and slid across the pan. We added a dipstick to the right side of the pan. It's calibrated for actual pam level. Not engine total capacity. Usualy run it at 7 to 71/2 qts. Lower than 7 I've seen the pressure drop on hard shut down. 8qts seems fine as well with the Master lube accumulator first fire up is about 11 qts in the motor. With the exception of when it ran without a windage tray and hurt #3 it's been flawless for over 800 passes. It runs 5w20 and 5w30 at a 50/50 mix. The current pressure is about 80. I've run it as low as 60 with no ill effects thru the traps at 7200-7300. If mine drops like yours I've never noticed it in the car. Of course thats looking at the gauge at 147+ going across the stripe
Doug

You still have plenty of oil pressure, I wouldn't worry about it. Now, that water temp is a little high.


Joe

Is it not just at/opening the relief? Maybe try thinner oil? Nice power!

I had 10 in for the whole system. I modified the pan so it has a space for a dip stick. I can’t rely on the factory marks though because I have the pan spaced down.

How much crankcase vacuum?

X2

Wasn’t an option. Not sure on the vacuum. It doesn’t have a vacuum pump so I’m sure it had pressure. I’m going to pop the pan take a look at the bearings just to make sure it’s happy.

Thanks, it’s just a street/strip build. Didn’t think about it could possible be pushing the relief valve harder….

Fkn send it...FWIW I have NEVER run a dual line set up and never had an issue and all my stuff is well above your target RPM. Thats PLENTY of oil pressure.

Im no expert at all, but i will comment because at my last dyno session, oil psi was played with to get more power. If you look at the pull, the psi has only dropped not even a full 4 lbs from start to finish, It sould be a lot of things, Oil return, slight aeration begining, etc . In my opinion i would say its not anything to worry about at all, As pointed out by Al its got plenty of pressure . For what its worth, my engine at 8000 had less pressure that yours, it is a wedge with oil lines returning to the pan and it has a vacum pump. But as i pointed out, they LOWERED my oil psi looking for power.

What number did you end up at? What oil viscosity? How much power was it worth? i've run less than the current 75-80 deoending on oil temp. Just been to lazy to adjust it.

Doug

ended up with 5400 = 67.7 , 8000 = 73.3 . it only gained 4lbs the whole pull. the oil is 10w40 . The first couple pulls the oil psi was dropping and we added one quart. But the psi was in the 80's, honestly i dont remeber how much HP it gained from just that. I know its not a big deal here, but i really dont want to talk about HP numbers.

It would be interesting to see if there was any temperature change in the oil itself.

What rate of RPM per second gain were you making that pull at? 300 per, 600 per or?
the reason I'm asking is the oil will get stirred up more, aerated, at the slower rate and that may allow air bubbles in the oil to compress and loose pressure

Doug
[/quote]

ended up with 5400 = 67.7 , 8000 = 73.3 . it only gained 4lbs the whole pull. the oil is 10w40 . The first couple pulls the oil psi was dropping and we added one quart. But the psi was in the 80's, honestly i dont remeber how much HP it gained from just that. I know its not a big deal here, but i really dont want to talk about HP numbers. [/quote]

Didn't need to know your HP, just curious if the lower pressure showed any meaningful gains.
Doug

What you don't run around with 2000+ degree water temp?

ended up with 5400 = 67.7 , 8000 = 73.3 . it only gained 4lbs the whole pull. the oil is 10w40 . The first couple pulls the oil psi was dropping and we added one quart. But the psi was in the 80's, honestly i dont remeber how much HP it gained from just that. I know its not a big deal here, but i really dont want to talk about HP numbers. [/quote]

Didn't need to know your HP, just curious if the lower pressure showed any meaningful gains.
Doug
[/quote]

I’m not
Sure , we made more than one change at a time. But it did help , I’m sorry but I don’t have a number

Not relative to your post on the small oil pressure loss at the upper RPM, I have seen a 8 HP gain on a wedge motor letting the oil temps go from 130F to 160F
Ended up switching all my street builds to either 5W20Wt or 0W20 wt. Valvoline standard oil, not synthetic, and saw no gain or loss of HP going from 80F up to 220F oil temps