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

I run my wifes van with a 200,000 mile 5.9 magnum on 0w20, I run all my hemis on 0w20 and even my 6.4 in my 2011 3/4 ton with piston oil squirters and a "low volume" 5.7 oil pump still never drops below 20 PSI at idle even when the oil temp got to 230F

I would think as the run or dyno pull progresses, the heat generated by friction at rod and main bearings, for starters, would heat up a lot right before it leaves the bearings, then mixes with the oil in the pan, heating that up some? So a straight weight 50 would change the most, a 0w20 the least. Sound logical?
That seems to make sense to me.

The thicker and cooler the oil is the more power is gain by getting it hotter, 10W3Wt gained 3 HP from 120 F oil temps going up to 170F oil temps, if my memory is accurate still
5W20WT no change in HP with cool or hot oil

Cab, what is the lightest oil you have succesfully run in a big block, say over 800 hp and over 7000 rpm? I assume bearing clearances would be tighter?

Just for info, typically we will drop from 70 psi to 60 psi during a pass at the track. This with a vacuum pump pulling a max of around 12 in/Hg by the end of the pass from a 5 in/Hg start. Water temp also increases by around 10 - 15 degrees F. According to the racepak data.
No ill effects bearing wise and we usually run the pan as low as we dare with the oil just showing on the dipstick. Also have a Canton accumulator in there too.

I once in desperation had to go off brand choice, oil wise and ran some cheap (ish) 10/40 mineral oil rather than my usual 20/50 valvolene racing stuff. Car was noticeably quicker in the 1/4 and we ran 4 small pb's that weekend, it was the low oil pressure when hot idling that put me off from continuing to use it, 25 psi IIRC. The next race meeting we were back on the usual oil and back to the usual et's, It took a cam. intake and carb swap to best the ET's we ran that weekend.

I have run my 4.15 stroke 502 engine to 7500 with 60 PSI of oil pressure too. Mine doesn't drop however. Stays 60 PSI from the hit to the stripe. I struggled with oil control issues in the pan when I made it quicker and ended up going with the single line with the Indy swinging pickup and the Milodon flat pan (tube k-member) and that completely fixed my psi drop at launch.

I'm not entirely convinced but I think that the Vacuum generated in the pan (which increases with time and RPM during the pass) may have something to do with the oil pressure dropping as I think the sensor "sees" pressure relative to atmosphere ??
Dual line and an accumulator, aIso run a long sump too, but modified for steering link clearance. A class we run in, required "stock type" suspension. Though I'm sure the rules are open to interpretation as there is a mopar with coil over front suspension competing now

No way that's on pump gas.

It does, but mine was dropping 30 or more PSI on launch and I only pull 10 psi vacuum. I pulled the belt one day and made a pass and the overall pressure was slightly higher but still dropped.

Vacuum doesn't affect my pressure readings at all that I can tell. In the answer to Gregs question on viscosity. As stated mine runs a 50/50 mic o 5w20 and 5w30. Bearing clearances are .0027 Rod/ .003" main.
Doug

I've never had a motor that liked to be revved over 7500RPM, I used Valvoline VR10x30 oil in the last race motor that ran 8.86 at 150.+ MPH in my S/P car that weighed 2850 lbs. with me in it, 5.50 at 125 MPF at the local 1/8 mile track in Madras, OR at 2500 ft. elevation.
I use to shift it at 7000 RPM and decided to move the shift RPM up to 7300 RPM at Woodburn, OR (1/4 mile track) and the car ran exactly the same ET but pick up 2.0 MPH in the last 300 ft. 45 minutes after the other run in the morning in time trials: confused:

Tig, i see 25-30lb at a hot idle [1000rpm ?] as ok, as long as when you go above idle, it shoots up.

it was also mentioned about a 200k van using 0-30 ?
my "bus" with the 3.3 engine [175k] gets 15-40, but i haven't gotten around to put a pressure gauge on it.
i'm considering going to 10-30 on it, but i just did an oil change about 500 miles ago, and since i don't drive as much any more, i have been changing at 2500 miles.
a big WIX 51515 filter also fits, so i have been using those for years. however, with WIX now being made overseas [?], after i use up my stash of 51515's, i don't know what brand of filter i will use.

Like others said, Send it! Mine did the same last time it was on the dyno. There is a chance the single line is contracting or sucking in creating a slight restriction at high rpm; you can put a spring in the line (Call Todd @March Performance) and/or use a larger line. If you have the indy maxx block and have not opened up the lifter valley (cut a hole to create opening or direct line of sight to timing chain) it can cause this as well. Essentially there is no access lifter valley and the lower crankcase once the engine is running. This because the only opening between the lifter valley and crankcase are the oil return holes. The oil return holes are covered with oil shortly after startup and at high rpm the return holes never clear off. Once that happens the oil in the sump is being sucked by the pump but resisted in the crankcase because it is now effectively creating a vacuum.

I have not run anything thicker than 10w30 for YEARS, no reason to. If you run an aluminum block when they get hot oil pressure can get quite low at idle. Like 15-20psi depending on clearances when assembled. As long as oyu have pressure and it responds to RPM no worries. I dont like to run as muchb pressure as the OP is showing. Its just costing some power, not really enough to worry about unless you are a heads up racer. Most my stuff I try to keep under 70 period regardless of RPM. I have had a few engines that are happy above 7500rpm but no reason for 90lbs of pressure then either. Unless you are talking about a blown hemi deal or similar I suppose.

FWIW I always run a single line if its a wet sump deal. Usually try to use a -16 line and ALWAYS use a spring in the pickup line. Everyone who sells AN line also sells springs for them. Loosing a bit of pressure at the top rpms on a dyno might just be an oil control issue, or lack of adequate drainback. On ther dyno the engine is static no g forces trying to move the oil and it can have a tendency to "pool" in spots that may be an issue on the dyno. For instance with the Vette we have to run almost 10 qts of oil in it on the dyno, on track we run no more than 7qts. And whenever we see a trend of oil pressure going down on a run we simply ad a little oil and its right back where it was.