Hello from Houston. I want to lower the oil pressure on my 71 383 Cuda that pegs the dash gauge when cold and only comes down slightly when hot. I installed a spring gauge and confirmed 80+ cold and around 80 hot. I had a friend rebuild the engine in 95 and he put a high pressure oil pump (M63HP) on it and I run 10-30 oil. I found an old post on this site that discussed oil types and high volume pumps but not high pressure pumps ( https://board.moparts.org/ubbthreads/ubbthreads.php/ubb/showflat/Number/4589685/site_id/1 ). O'Reilly sells three different pumps, standard, high volume and high pressure.

Why high pressure over high volume or even a standard pump?

The old post mentions adjustable springs for pressure, do they still sell these?

What oil type? Can I, should I consider synthetic?

In addition to all this the engine has a knock which is another post but I will see if an oil pressure reduction affects it.

Thanks, Kevin

High pressure increases pressure.hi volume increases the amount pumped Ie say 10 GPM vs 20 GPM.There are adjustabe springs avaliable as far as I know.I beliebe Moroso makes one.There are different springs avaliable also.I run 20 50 most time.My 440 runs hi volume hi pressure pump whic were avaliable when it was rebuilt.Runs 80 PSI just about all the time.been like this since at least 2000.Never a problem.I run kendall GT1 when i can get it.Some dont like hi pressure I do.Rocky

80 ain't gonna kill you tho it stresses the intergear more (not a dealbreaker as everything gets stressed) but unless this is a high RPM screamer I'd want less. what I do is (1) get the wt of oil that I am comfortable with (as light as I can safely run & not sure if straight wt is better than multi or not) then (2) go with the pump/spring needed. I'd get the O'reillys std pump (they're cheap), clean it & bolt it on & see what you get for psi. another option would be to cut a coil at a time off of yours

You can lower the oil pressure several different ways, replace the high pressure spring with a standard pressure spring, trim one to two coils off the high pressure spring or change the pump I use a good set of side cutting wire cutters to trim 1 1/2 coils off most of the high volume pumps I use That normally makes the pressures drop some on most of the motors I've done this to, starts and has 80 lbs cold(below 40F) at idle, 25 to 40 lbs idling when warmed up with 10/30 Wt oil. 65 lbs at 6500 RPM with hot(above 160F) 10/30 wt oil On my old 518 C.I. low deck pump gas stroker motor with real loose oil clearances throughout the motor it would have 18 to 20 lbs at 650 RPM with 180F+ oil temps, 30 lbs at 1200 RPM and 65 lbs at 2000 to 7000 RPM with that oil temp. with 5/20 WT straight petroleum non synthetic Valvoline oil

I'm having the same issue. Just fired up my freshened race motor. Indy single line pump, standard body. Lifter bores, mains, and rods are all on the high side of tolerance. It has 80psi@150 oil temp @ 5000 rpm. It used to run about 60-65psi through the lights at 7100. When it was pulled apart the relief valve spring was broke in half, pump gears were chewed from a broken valve spring, cover was scored. I milled the cover replaced the gears and spring. It has an adjustable pressure relief which is backed out as far as it can go. Has the 10/40 break-in oil in it. When it gets the 5/30 synthetic looks like I might have to trim the spring.
Doug

this will let you put it where you want it [ within a given range ] while it is on the car ! http://store.440source.com/Adjustable-Oil-Pressure-Regulator/productinfo/200-1093/

Its not broken don't fix it Yesrs ago I raced a 340 demon with 40-psi and only slightly less with heat ran fine and would go 6K easily. My old 318 pickup only had 20psi period due to clogged pickup and it ran for 3 years like that?

This is the combo right here.^

As for spring vs volume. Why correct this problem with a spring. What is the point of having the oiling system constantly running on bypass? It's done because it's easy.

Once an engine is clearanced. It should be tuned in with pump volume to achieve the desired numbers. Not too much volume and bypass until you are happy.

I've corrected too much pressure many times on fresh motors by switching to an old worn out stock pump.

the above makes VG sense (I learned something today). My thoughts: (1) get the clearances where you want em when you build (2) pick reasonably light wt of oil (3) start with std vol pump & go from there

Here is a possible solution...

Adjustable oil pressure regulator..

http://store.440source.com/Adjustable-Oil-Pressure-Regulator/productinfo/200-1093/


Just my $0.02...

Mine has one. PSI still to high. The first thing I would do is try thinner oil. My race motor has been running 5w/30 for 300 passes at 65 psi@7100. Rod bearings looked perfect mains not bad considering the power is (close to 900). The adjustable regulator which is turned down all the way. It does have the tall rotors (high volume). Idle psi is 55, 75 at speed after cutting the spring by one coil. It still has 10w/40 oil fo break-in . My bet is that with the 5w/30 it'll be real close. If not I'll lop off one more coil.
Doug

For me around 20psi at idle is what i shoot for. 60psi on the intermediate shaft during idle is never good. Lots of strain. The old rule of thumb 10 psi for ever 1000rpm is more than enough.

My pump has a metal tag stamped M63HP and the plain color (black) spring. I purchased a standard pump repair kit and the rotors in the kit are identical to the ones in my pump so it appears that the only difference between standard and HP is the spring (I apologize if someone already posted this information). I have also ordered an adjustable regulator from 440 Source (thank you very much for this info). Paperwork with the kit states that idle pressure is not affected by the spring selection which supports the thinner oil approach. My plan is to return the kit, install the adjustable regulator on my original pump and experiment with oil. I will start by going to 5w-30 from 10w-30.

Regarding the note that advises to rotate the pump while submerged in oil, is this for priming? What to do if I don't have the clearance to install the pump assembled (I had to split the body to get it out).

Thanks for any guidance, Kevin

Your oil pressure is fine. Leave the fly poop in the pepper and move on. I'd rather have 80 at idle than 20. Unless it is DEAD stock.

Your hope that reducing pressure will cure a knock, is nothing but wishful thinking IMHO

I want to reduce the pressure because I don't think it needs to be that high. I don't have any hope of a pressure change curing my knock, but am interested to see if a change affects it.

You want to reduce the pressure for the same reason EVERY car manufacturer has reduced the pressure.

It wastes fuel and robs power. There is a pressure that is too low and pressure that is too high and there is a super wide margin in between. The smarter of us run near the low side without going under.

Are you using a electric or mechanical gauge?
I wouldn't worry about the cold oil ressure at all, never If it has reasonable oil pressure, at least 10 lbs per thousand RPM, with hot oil running down the road your golden

If you want to reduce the hot oil pressure then you need to reduce the pump volume. Put a std volume pump in there and see what it does. If that reduces the hot oil pressure too much then put the high pressure spring in the standard volume pump and you should be in good shape.

Original elec in dash and a mechanical mounted on the engine to confirm that it is actually running high as the dash gauge shows.