Mopar Street Big Block Oil Pressure

I need some advice. My engine builder assembled my 499 stroker. The bearing clearances are on the loose side with the rods at .0026-.0027, and the mains are .0031-.0032 and number 3 bearing at .0034. I ran a standard psi/standard volume melling pump. Oil pressure at 6000 rpm on the dyno was at 53 psi, but the engine was only 160 f.

Before installing the engine I replaced the oil spring to a high pressure spring.

Now that I have the motor in the car and the ambient is 90f and running at 195f water, I can tell that the oil pressure is lower. At idle it is at 15 psi and 5000 rpm it is 53 psi. I haven't taken it to 6000 rpm yet but I can't see getting more oil pressure than that. When you increase the rpm the oil pressure does react quickly.

Is this okay to leave it like this or should I be looking at a high volume pump?

You could put the HV pump in there to see what it does. That is a fairly simple experiment to run. Sometimes the best solution is a HV pump with a standard spring, other times you need the black spring.

AndyF, I only have a 3/8 pickup. I am running a 7 quart pan with a good windage tray. Is the pick up okay?

I run a basic HV pump on my 493. I set my clearances a tad on the loose side as all the mains were about .003 and the rods in the .002 to .0025. I just looked close at my car friday as I took a 90 mile round trip and it runs about 30 psi when hot (195) at idle and about 70 PSI at 60 mph which is about 3200 rpm cruising down the road. I am using Valvoline 20W-50 VR1 racing oil though. Ron

Way better to have to much volume and pressure than needed I would install the high volume pump as is but inspect and clean it before use, and then see what pressures you end up with
I normally use that pump on all my Hi Po BB builds, I will trim some coils off the black spring if needed, IE a street and strip motor that will see 6500 RPM max I will shoot for 65 lbs at 6500 RPM with hot oil(160F+) on the dyno or in the car On your deal if you decide to reduce the pressure on the high volume pump do as AndyF suggested, remove the black spring and put in the other spring from the standard pump to see what that does for you I have added shims(thin flat washers that will fit in the bypass valve cup between the srping and cup) to a standard pump to icrease the bypass pressure.
Let us know what you decide and find out, it will help others on here

Gentlemen, thanks for all the feedback. I will try the high volume pump.

Can I run the standard MP oil pump distributor gear with the HV pump? Do I need to pull the distributor and oil pump gear to replace the pump. Or can I just pull the oil pump?

(1) I believe so but wait for the BB guys to chime in. (2) I would have the pump bolts barely snug then insert the intergear then final torque the pump bolts for dead on hex alignment. I want to ask what weight of oil are you running? I would want the lightest weight you can get by with & still have adequate psi

Hey RapidRobert, I am running 15w50

Alright & I ain't enough of an oil guy to know if that is thin or thick oil (or somewhere in between)

I agree the HV pump is a good solution. With the higher clearances you need more flow, especially hot idle. It has worked well for me on my 496 with 3/8" pickup. Usually the relief spring as supplied is about right though there can be variation.

The HV pump needs a strengthened drive gear for reliability. Key improvements are hardened hex, radiused transition from hex to shaft and pinned gear. Higher loads with the HV pump can fail the stock piece. Mancini and others have them.

Oil viscosity can be used to "tune" the pressure. Mine likes 15W40.

I run a stock drive on my HV pumps with no problems at all. And go ahead and try installing the new pump with the drive in place. Spin the pump back and forth as you slide it up into place so that the hex can align. If it fights you, you can always bump the engine over a bit to help align the hex.

Question; Does the HV pump have that much more resistance to turning than the std pump? It would seem that the pressure would impact the resistance more. At say 60# pressure, how much harder do you think it would be to spin an HV pump over a std pump?

the HV pump would probably help lower rpm volume but may not add a lot of volume in the upper rpm due to the 3/8" pick-up. anyhow, i use an HV pump with 1/2" pick-up and stock low pressure spring. hot idle in gear is 40lbs, running pressure 60lbs with 30wt oil. my bearing clearances are a little tighter.

me to for higher RPM/spirited driving I think adequate area on the suction side is important (1/2 pickup & a bit more mods upstream). I want adequate area (pressure side as well)/correct bearing clearances/correct (as light as possible) oil weight/bypasses as some journals can be starving tho the gauge at the beginning of the system (rear of the block) shows an adequate number) THEN see how much pump/spring I need to obtain enough psi

15w50 oil? That seems a bit overkill. I'd put some 10w30 in there and see where you're at. The thick oil is hard to pump so the engine doesn't get as much oil flow.

He'll have less pressure with 10w30. 10w30 and a HV pump might be the perfect combination though.

between loose bearing clearances and probably wide rod side clearance the bottom ends a "bleeder". this seems to be very similar to a build i had a couple of years ago. mine was 18psi hot idling in gear with a heavy base stock 30wt oil and half groove mains. i tightened the bearing clearances up (.0005"-.0007" tighter), got rid of half the rod side clearance (i will never believe side clearance doesn't effect pressure. it's a hole, it's a leak!) and more than doubled low rpm pressure (with added full groove mains) and the engine runs smoother

Same issue. Stock melling pump with the heavier spring. Running 15/40
Idles at 20pds hot and cruises around 6o-70 hot

You'll be fine with the 3/8 pick up.

If you insist on running the thicker oil then I would seriously consider upgrading to the HD oil pump drive ... i would do it no matter what oil ... it's cheaper than the cost of rebuilding the motor if the hex shears off.

John,if you knew what I have been running in my bird for 33 yrs you would be

Thanks everyone for all the great feedback. I will try the HV pump with 10w40. I ran 10w40 with the current pump and yes the oil psi was even lower.

Does anyone know if the Mopar Performance Distributor gear is a good match these HV pumps. The MP catalog does mention that it's hardened, or should I just order the Milodon distributor gear? Any other distributor gears that you guys recommend with HV pumps?

Higher oil pressure from thicker oil isn't necessarily a good thing. The higher pressure just means that the oil isn't flowing thru the engine very well. The pressure rise is due to reduced oil flow which isn't necessarily a good thing. The bearings need some oil flow across them to carry away the heat so less flow could be bad.

60 psi with thick oil and a standard pump could be a lot less oil volume than 60 psi with thin oil and a HV pump. People tend to focus on oil pressure since almost everyone has an oil pressure gauge but oil flow is also important.

Very good point Andy.

Yes I agree. Ron

You may believe it or not, but the laws of physics don't change for your beliefs

You do realize that the oil "leaking" from those gaping side-clearances had to come from the oil passage in the journal, pass through the much smaller bearing clearance, then exit via the side clearance? It's a series circuit and the vast majority of the resistance (to fluid flow, just as with electricity) comes from the most restrictive part which is the bearing clearance...

On the heavy duty pump drive... the MP piece I purchased > 10 years ago has worked well for me.

Bill you're crazier than me


He asked for opinions and I gave mine to his situation and the small cost outweighs the cost of a full rebuild. 53psi at 6000 rpm is a little risky to me.

Pick your poison

no disrespect, but i don't agree. my real world experiences say side clearance is a leak.

Side clearance is a clearance just like bearing clearance, the wider the gap ....

Yes, and so is header clearance. Not the point. Please go back and read my post more carefully ... where does the oil (that's escaping from those side clearances) come from? That's right, it's already been through the tightest restriction, the bearing clearance. It is NOT an "independent" leak stealing oil directly from the pressurized galleries and dripping it back to the pan!

So the effect of a wide side clearance is very small (if not absolutely negligible) compared to bearing clearance. As many guys who have put Chevy-width rods on Mopar-width cranks have discovered, with plenty of oil pressure.

Meanwhile, go on believing as you please. No point in trying to teach something to people who already "know".

So you have some identical engines that differ solely in the rod side clearances, and the ones with tighter clearances have more oil pressure? NOTHING is different but that? Same operating temps, oil viscosity, brand, etc. etc. Please provide more info here... If I'm wrong, I'd love to know why other than just claiming "real world experiences". (The plural of "anecdote" is NOT "data").

Also no disrespect intended, of course, but I've met far too many people in my life who know things that just ain't so...

I've got a build pretty much like original poster myself and have similar pressures via stock replacement pump. Decided to run 20-50 as the car is summer weather toy anyway. Pressure now stays at 20 psi min and up to 55 or 60. On the side clearance issue, I've built a bunch of industrial diesels with GOBBS of side clearance from the factory, so it's not a huge pressure loss as ya might think.

Correct. The governing pressure drop is going to be the tightest (smallest area) flow in the system. Once the oil has squeezed through the bearing faces, it is basically open to the internal of the engine. If the side clearance was zero, there would be no flow but you may not necessarily see infinite pressure because of oil flowing through other parts of the engine (the next largest open areas). Once the side clearance is equal to the bearing clearance or greater, it no longer has a significant impact on pressure drop.

By this logic (which I agree with) is 53 psi necessarily a bad thing? From my limited understanding of journal bearings, as long as there is enough oil present to support a hydrodynamic layer, the feed pressure isn't that critical. It's hard to picture a bearing being starved at 53 psi or for that matter 30 psi.

Now you can point your finger and laugh,65 Race Hemi rods and main bearings,standard crank,from 20/50 Kendall GT1 in the early 80's to Brad Penn 20/50 now,65 psi at idle hot and roughly 75 + at 3K,never had a problem,thats how we did things 30 yrs ago.This is what it looked like after 30 yrs when I changed the intake gasket last year.

The general consensus on BB and SB Mopars is 10 lbs of oil pressure for each 1000 RPM, so a motor shifted at 7000 RPM needs to have 70 lbs of pressure at 7000 RPM No matter what weight oil or the oil temps. I got away with 65 lbs of oil pressure shifting at 7000 to 7500 RPm with 5W20 WT oil at 160+ F oil temps in my old pump gas 518 low deck stroker motor with BB Chevy rod journals with .003+ bearing clearnces on the rod bearings and .0035+ on the mains It had from .054 to .035 rod side clearances using a set of 6.800 long BB Chevy type H beam stel rods also, it went against the grain on a lot of the old myths posted on here

I think NASCAR engines run 9000rpm @ 50 psi oil pressures.

Volume peeps, volume.

So I will be happy with my 20lb - 60lb hot

Aren't they running that with a mere half thousandth of bearing clearance and oil as thin as water?

To the OP and everyone else who tried answering without thinking things through: 15psi at idle and 53psi at 00 rpm are very much in line with the old "10psi per thousand rpm" rule of thumb. Why change anything? Your question seems to be based in ignorance. The first responders should have gone there first. Another thing: bearing clearances. I didn't see any bearing clearances that were out of line with what's been suggested here lately.

If you must do anything, add a high volume pump, you can do that from the outside. No need to mess with the spring. No need to disassemble the engine and add a 1/2" pickup. Maybe that's worthwhile on Hemis running 7000rpm for hours, NASCAR 1960s style, but for a street engine it seems to be just another way to screw up a perfectly good block.

IF you have all the money in the world, eliminate the internal pickup and use an external pickup setup, but it is clearly not needed on an engine that just the way it sits has 53psi hot oil pressure at 5000 rpm.

I don't care what oil pump you run, I'd change the pump drive/distributor gear to one that doesn't have a sharp step between the shaft and the hex. That is a stress riser or concentrator. Just from the mechanical design alone it is wrong.

As to the other items that popped up, fluid dynamics is not intuitive. That's why I had to take it twice. The second time through it popped into focus. Then I spent 19 years designing pump systems.

R.

I am running a HV pump on my hemi and the pressure was over 100 cold to 75 hot at idle with Brad Penn 10W40. I switched to 5W30 synthetic and now it's 75 cold 25 @ idle hot 50@ 3000 and maxes out a little over 75. The engine runs a lot happier.