This is a great explanation why you never run HV pumps on the street as it is unnecessary.....written two years ago by Jeff Smith:

​​​​​​https://www.onallcylinders.com/2023/...20the%20engine.

Anybody can do whatever they want.......but if you are running a HV pumps and pushing more than 60psi of pressure under any circumstance.....you are doing it wrong......big Oil Pressure number may give you a half chub sitting in the car revving it.......but know that over 25% of the oil is just blowing out of the bypass over 60psi......and if you have an 80psi bypass.....you are just sucking more power and putting stress on the oil pump driveshaft......
Having 60psi at idle hot is stupid.....not needed and just pushes extra oil up top that has trouble draining back anyway.

Consider that the 302DZ (you know, which revved to 10,000 rpm all day hopping coke cans on pump gas)....and the LT-1 did not come with HV pumps from the factory and that really should say enough.....

Prove me wrong.

Jebby

 

I just ported my stock oil pump so that is flowed more oil to the engine vs backing up at the poorly shaped pump exit point.

 

 

Very common....I chamfer the recieving hole in the cap with a burr....most high end shops do....smooths the flow....

Jebby

 

I tend to prefer clearances a little looser...but I rev the devil out of them. With a HV pump in my engine I idle around 25 psi...and hit 75'ish at the upper end at 7000-8000 RPM. The HV pumps do a good job of "outrunning" the leaks caused by pressure fed solid roller lifters, turbos, loose clearances etc. I also tend to put a lot of oil to the top side to keep springs cool since i drive on the street and highway a lot.

Z-28's used a higher pressure spring in a stock pump to kick up the pressure on the top end a little. You can make 100+ psi with a stock pump if you have enough spring. HV pumps just get there quicker...the spring and pressure relief set the max pressure regardless of pump size.

But I agree.....many folks are running around at low speeds with the pump on bypass and that's bad. It creates aeration/foaming in the oil and will starve the engine of a steady oil supply when it needs. Oil pressure needs to steadily increase as RPM builds. You don't want it pegged while riding around at 60 MPH.

That said....some OEM's ran 100+ psi on their stuff back in the 60's and it worked fine. They were using pressure to deal with other issues. Not the best way...but it worked in certain applications.

If folks run tight tolerances, the machine work needs to be dead on and the parts top notch to not move around too much.

Melling has some good info on their site also.


JIM

 

Just block the bypass and filter all the oil. You need a strong truck oil filter, a pump with hardened gears and a lot of oil because you will have a lot of pressure in the filter and alot at the top of the engine. Racers have been doing this for years, especially since they tend to break things from abuse and want to keep the crap out of the bearings if they can revive the rest of the motor. Ive run a high volume pump, no bypass, K&N truck filters for the volume and rev my 427 mk IV to 6400 which is where my rev limiter is set....(bumping that to 6700 rpm this winter) with zero performance issues, just bad gas mileage from the pedal meeting the floor. I run 15w50 or 20w50 depending on what Walmart has in stock, both for the ZDDP BECAUSE Im running solid flat tappet EDM lifters and for the thickness to keep the oil in the bearings at higher rpm.. My pressure is around 70 psi when cruising and 50 psi at idle hot. I can go from idle to 6500 pretty quick and I dont need to wait for the oil to catch up. The truck filter is taller and has that much more filter element so more filtered oil will get through so it isnt backing up in filter which could cause it to blow out. If it got really high the K&N filter has a bypass that opens on 11 psi differential pressure, so if the pressure on the upper engine side goes down, the bypass opens to let more oil up there.....not an issue

If its a very hot, thin oil you wont have the cushion that the bearings are designed to have. If the crank contacts your babbit it will score it and will continue to get worse and worse creating a space too big for a thin oil to fill. It will compound the damage. I also want as much oil on my cam an if my lifters so they dont get damaged either. I prefer to push as much oil into those bearings and let it sit there before it slowly gets pushed out. I run a 7 quart baffled pan with a kick out and crank scrapers so what oil is in the pan is right at the pump. What isnt up there is at the top coating the springs and rockers.....oil isnt a problem. Ive changed it twice already this summer and probably will again shortly just to keep it clean and have it somewhat fresh while its in storage for the winter.
If you design and build it right and use common sense plus doing some some decent reading, you can build it to last. You just dont/ cant believe the internet builders that buy parts and just put them together or spout things because they will work IN THEORY. Never had an engine fail for lack of oil. Had a 327 430Hp motor fail on broken CompCams solid roller lifters on a hydraulic cam, not oil related, just bad lifters breaking the wheel tangs off, possibly due to being needle bearings and not bushed bearings. And had my 427 famously fail due to bad crank to rod bearings. THose delaminated and fell out of the journal in traffic getting on the highway. Very disappointed since I wasnt being immature or having fun at all when it happened. THat was at 500 miles when I was just getting the paper and heating the third oil change since break in. I had many large pieces in the pan and posted pics of those. Those were Clevite bearings. Went with King triple babbit bearings and they take abuse.
many miles since then and still dishing out the fun.

What you will hear here is a lot of experience from what these guys have built over the years and what has worked for them. A lot of these guys have been racing for 30 to 50 years. Some are in the 200 mph club. But we all do what has worked for us and rely on that information. I like high volume. Used a high pressure pump once but didnt really get any benefits from it, dont suggest using them either. You cant go wrong with more oil in the bearings, just make sure its filtered so they survive, make sure you have the surface area to get it there, make sure it stays there and dont cut corners in a build.

 

From Google AI:
"For a 500-horsepower V8, rod bearings can experience peak pressures ranging from approximately 6,000 to over 10,000 psi."

A 60 psi vs a 100 psi pump is not going to make any difference there. The pressure in the rod bearings is exponentially more.
What matters is FLOW. But I do not know of any engine that uses an oil flow meter.

"...a standard cam-driven SBC oil pump typically flows around 3.1 gallons per minute (gpm) at 1.000 RPM"

More RPM generates more flow, since it is a positive displacement gear pump.
Since the psi usually tops out at around 3000rpm, I would guess that is about a 9gpm max flow, thru the engine.
Then the bypass spring opens. The engine will not take any more flow.
Spinning the pump higher, does make more flow, it just goes out the bypass.
High Volume pumps just get to the max flow/max pressure point sooner, and open the bypass sooner.
What is the advantage?

High rpm throws off more oil, faster, from the spinning crank.. So more flow is needed.
What happens is the bypass closes down some, so the psi stays the same, but the flow goes up.
If you open up the rod clearances a lot, like they did in the old days, (they thought loose was fast),
That increased oil flow a lot. And the bypass would shut more, maybe all the way. And the pump still could not keep up, with all the leaks, and at high rpm, the oil psi would nose-dive.
Not good.
So the "need" for high volume pumps developed.

Unless that is happening you do not need a high volume oil pump.
Most people do not build engines that way anymore. Not street ones anyway.
SBCs have some of the best oiling on the planet, and stock oil pumps, and stock clearances, are fine to 6500rpm or so.

More psi does increase the flow thru the engine restrictions, to compensate for a little more high rpm "flow".
Therefore the higher psi spring in the high rpm 302 and LT-1 oil pumps.

8,000 rpm is a whole different animal, especially in a big big block, like 427 hotrods.

 

You should eliminate the Google AI part of your response.........AI is full of garbage, it scours the internet and doesnt know the difference between truth and bubba....just regurgitates whatever it finds....it would be more believable without it
Closing the oil bypass solves all those issues, just use a racing filter

 

But when we speak of bypass, we are talking about the oil pump pressure bypass.....and just about anyone with an HV pump that pushes more than 60psi is riding around with this pushed open all of the time....and even more at every acceleration.

You can go wrong with more oil to the bearings....if the clearances and restrictions push your oil pressure over 60-70psi at max rpm or around town....it is just flatout unnecessary.....and once you hit the bypass you actually reduce the amount of oil being transferred.

Your engine is your engine and that is cool....but I will not build them that way because it is outside the parameters the equipment is designed for.

And I will always ring a word of caution to a crate motor company that builds them this way too.....as they should know better but choose to do what they do.

Go purchase a crate motor from Nelson, Reher-Morrison, Musi...etc....and it will not be built that way.
I have mentioned before that I was mentored by bulders of this caliber many years ago.....they know what is going on in an oiling system....all these guys do now, and have for over 25 years....and once they did, their engines will have the right amount of oil pressure for the job.....


Jebby

 

Your engine and the how you use it are what all of the HV pumps are designed for.....and your clearances reflect that....you have a good insight of what is going on in there. You understand that pressure/volume and clearance is a balancing act and high pressure numbers are conducive to tight clearances....or volume overcoming the clearance that is set.
You can make 100psi with a stock pump given enough spring but there has to be enough restriction to do that.

My stuff traditionally is set .003 mains and .0025 rods. This almost always gives me the 25-60psi sweep when warm with a std. pump.
If I remove that pump and put a 100psi spring in it....it will still sweep 25-60psi....it just now has the potential to make 100psi before the bypass opens.....and this is where a lot of people get it wrong and confuse themselves. To actually make 100psi I would have to tighten clearances to the .001 area or close to it.....
That is too tight....even if **** is machined perfectly.....any particles that are larger than .0005 could get stuck and scored around on the babbit....this is important and never discussed either.

A 500hp street engine will not be setup the same way.....

A looser engine is a happy engine....any way you slice it....

Jebby

 

I get you Rescue. But my memory just isn't what it used to be. Pretty good stroke recovery, but some memory holes here & there.
And heaven help me if I quote a wrong number here, some keyboard warrior will jump all over me!
I just use it to confirm what I think I remember correctly.
And I agree with you 100%, there is a lot of junk info out there in internet land, but some of it is very good.
The trick is being able to confirm the facts and/or trust the source.
I taught that to my students for years. You should have seen the junk they told me sometimes!
My goal, both then and now, is to shoot down some of these old "myths" that have been floating around, some for decades, with science and facts.

I was speaking of the bypass spring in the oil pump itself. That is the one that controls the oil pressure.
There is a second bypass spring, near the oil filter, that protects the engine, in case the oil filter clogs.

I know many racers delete that one, and I suppose it might keep some broken debris out of the engine.
But that always sounded like an old racers myth to me with very weak reasoning.
If I break something, and I have, that engine is getting all the way dissasembled. Period.

And I have seen an oil filter blown off, in the race shop, with cold oil, with a filter bypass installed.
Can you say big mess?
It just seems like a lot of trouble to me, with as many downsides as upsides.

IIRC (there goes my memory again) a SB or BB only filters about ~60% of the oil volume, in certain instances.
Isn't that mostly when the oil is cold?
Then you have to be very careful warming up the engine.
But once it is warm, does it do anything?
But forcing all of it to go thru the filter? All the time? In those circumstances?
If it restricts the flow, the pump pressure will skyrocket, the pump bypass opens, and you will actually get less flow to the bearings.
And this is a good thing?
Has anyone ever measured oil flow?

Someone convince me why it is more beneficial to have a filter bypass?

You know me, I'm a science guy, I like facts, not myths.
Teach me.
What big name builders do it?
On which engines?

 

Yes, i am talking the bypass spring that routes oil past the filter. You are talking the pressure relief spring inside the pump. Read this from Grumpys sight. He points out that chevy pumps recirculate the oil inside the pump versus sending it back to the pan. He also states the Z28 stock pump is high volume. Ive read through sections of it multiple times.
https://garage.grumpysperformance.co...it-works.3536/
And the oil pressure at the gauge on a chevy is after the filter, so your oil pressure at the gauge is from passageway restriction and bearing gap restriction. You wont see oil pressure prior to the filters unless you add a oil filter remote mount and take pressure from that line. Actually not a bad idea to have oil pressure before and after to judge your filters contamination....
High volume isnt going to hurt a performance engine and is necessary depending on the build . It will not hurt a stock build either, but it is most likely very unnecessary.
Its a good read and very informative. 2 of the local guys recommending it in person was John Kippin who i highly trust, and has multiple wins in TA/FC division. And one of his builders who i believe is retired, Roger I believe of R&L machine, a third, Gregg Hekemian Hekemian Racing, also John Liggenfelters book on racing/ building SBC...Its pretty common in racing but you have to use a performance filter. Thats the caveat, high performance, high volume filter. I use the K&N 3003.
As for changing the pump pressure, i havent had an engine that needed a higher spring pressure while using a high volume pump and 15w50. My engines dont show oil wear in the bearings or cams and they run very cool...too cool on cold mornings. I am tempted to add an oil temperature gauge but havent had time to plumb it to see if i need to bother with an oil cooler. Being able to take heat away from the bearings with oil flow will also help prolong life

Heres a really good write up on chevy oil pumps and the oiling system again. While poking around i saw more and more builders are suggesting plugging the oil filter bypass on LS builds. I havent done anything with an LS yet, but if i do it will be an all aluminum 6 liter or larger

https://garage.grumpysperformance.co...it-works.3536/

 

I think there’s grains of truth with everything being said about oil film strength and cooling.
I am not a master engine builder or a professional race engine builder,
BUT
from my experience, with very very large bearings and oiling systems(journal bearing shells about a foot wide) when there is higher load a secondary booster pump is activated to raise pressure and flow. The higher pressure strengthens the oil film barrier between journal and bearing and the higher flow removes more heat from the bearing.

one might say, if HP/HV is good for crank shafts that weigh 2000 pounds, why isn’t it good for my tiny tiny SBC/BBC?

I personally think it is unnecessary in our tiny engines. Stock oil pumps are more than capable enough. Which is why I run stock pump

 

OK, all you oil pump pundits, a straight-forward question about sbc for y'all:

Premise is with No regard if pump is Hi or Lo Volume and with No regard if pump is Hi or Lo Pressure.

? Which is the better pickup tube diameter; the smaller 5/8" OR the larger 3/4" ?

 

When you compare stock 200 hp motors versus a 600 hp motor, the shock from the combustion process is much much higher and that energy translates to the bearing surfaces in the rods and crank, more so at 6000 rpm. At that point you want a stronger film with a higher sheer strength to keep metal on metal instances from happening.
There is a great deal of diiference in motors making 0.5 hp per cube to one making 1.35 hp per cube.
This conversation really has nothing to do with a stock motor making less than 0.75 hp per cube

 

Maybe two of Uncle Tony's videos describe this better than I can.

The first video describes how a canister oil filter works.
It has a bypass spring inside of it that opens at a 20 psi pressure differential across the filter media. Bypassing some % of the oil past the filter, some of the time. Particularly when flow is high. Metal chunks can get thru.


The second video describes destructive engine particles the best.
Jump to the 4 minute mark and the 10 minute mark.
The only way to protect your race engine, from metal pieces, from bearings or valve train chunks, is by using an Oberg filter.
It is just a fine screen but it filters 100% of the oil 100% of the time, and oil does not does not bypass it, ever.

Otherwise if you lose a camshaft lobe etc, those particles get thru, you will need to clean the oil galleries by dissasembling the engine, and scrubbing the particles out.
Honestly I worked at a drag race engine shop for 40 years, and they did not use these Obergs at all. And they saw a lot of broken engines. They just took them apart and cleaned them out.

 

Grumpy's site is very good indeed.

All the above comments are correct, except for one thing.
The Z28 / LT-1 pump is standard volume, and high pressure. High volume SBC pumps have 1.5" tall gears.

"12555884
SBC Oil Pump, High Pressure Z28/LT1. Production high-pressure oil pump with 1.20" gears. Will produce 60-70 psi oil pressure. Does not include screen. The pickup tube dia. is 5/8" for this pump.
62.17"

Grumpy quote and my engine builder / machinist's quote:

"I've always found the best results from keeping the low rpm pressure , in the 15psi-20psi at hot idle and no more than 65psi at high rpms, is really useful, the volume required depends on the way the engines clearances and oil systems designed or modified ,volume/viscosity/clearances in the approximately stock range works fine in most "

So yeah, if you open up the engine clearances enough, for the low rpm oil pressure to drop below what is recommended above, then you need a higher volume pump.
More volume, that gives more pressure than the above, is not needed, and is just a HP drag.

 

Im assuming you make 600hp and run a HP/HV oil pump?
I make 550ish HP and run a stock oil pump.
Neither one of us has bearing damage. That’s all I’m saying, stock pump is plenty.

 

Yes it is....if your clearances are setup so you have 25-60 idle/redline....that is enough oil. Period.
As far as combustion pressures go and load on the bearing....consider what I said about NHRA Pro-Stock running the 25/55-60 that I spec and consider it does it with a much smaller and narrower rod bearing....25/60 from a Pro Stock engine across the bearing is no different than a street 350....but the pumps volume and the clearances will be.....they run like .004 and have a bad *** pump to keep up......

The statement from Grumpy is correct....he gets it.
You have to understand the corrolation of clearance vs. pressure vs. volume to even begin to know what is happening and sadly most people do not.

Melling says its Z/28 pump will make 70-80psi....well, if your engine has a std. pump and makes 60psi max....when you bolt the Z/28 pump on it will make 60psi too....it has to, the pump is no different save for the spring. It will have to move more oil to create more pressure. If it does not, it won't. Simple physics.

The surface tension or meniscus of the oil is what keeps the crank from touching the bearing....higher pressure does nothing, the journal isn't "pressurized" it bleeds....more pressure at the gauge is just the restriction at the crank oil hole where it meets the bearing.....all the bearing needs is a good flood....anything more is unnecessary at .002/.003 clearances on the street....all you are doing is holding the bypass open and putting extra strain on the oil pump drive and distributor gear.....

Fun Fact: Bronze gears last twice as long with my oil pressure specs rather than the 60-80 psi everyone rants about.....given the same clearance, the differance between a std. pump and a HV is over 5hp.....guess where that power is being used.

Jebby

 

* I didn't look at those videos.

I've never worked in a "drag race engine shop" but have worked in an endurance race engine shop; and visited several others.
Oberg filters were de rigueur with many cars. However, most of those w/ Oberg filters also had dry sump systems.
FWIW, Oberg supplies different sizes of screen mesh; and yes, different width filters as well. Oberg is USA.