is there a way to raise the oil pressure on an lly.what controls the pressure on an lly.i have noticed that the oil pumps have the same part #.so how do i get my new lly motor to carry lb7 pressure.i also now have a spare engine to experiment on.

why worry about it? you have made it to 180,000 miles without a problem. why start messing with what the GM engineers see fit for an oiling system?

remember, low oil pressure is not always a bad thing, because pressure is a resistance to flow. I noticed when I switched to synthetic oil that my pressure dropped a bit. Didn't the LLY move to a higher volume lower pressure system as opposed to the LB7?

without a problem.right up to the time the motor started knocking.

without a problem.right up to the time the motor started knocking.Are you sure the knocking is being cause by "low" oil pressure? I've read here that bad injectors can cause the engine to knock really bad. You may want to check that out before you start tearing into guts of the engine.

Are you sure the knocking is being cause by "low" oil pressure? I've read here that bad injectors can cause the engine to knock really bad. You may want to check that out before you start tearing into guts of the engine.
no,its caused by the metal on metal contact.):h we are getting off topic.all i want to know is there a way to raise the oil pressure in an lly?

You should be able to change the relief spring pressure in the pump to change oil pressure. IIRC

I recommend Lucas oil stabilizer. 2 qt's at each oil change will give you great oil pressure under the worst circumstances. Use the regular in the summer and the synthetic in the winter! I've used it in all my D/A's for many many miles before I installed the EOC without any problems!

If you need to use and additive in your oil then you need to use a better oil. As for the relief spring in the pump that won't change a thing. The spring is set at a higher pressure than what you run at normal operating temps. When cold pressure will go to about 70psi. It won't go higher because the relief is now open. I was told of a valve somewhere on the motor that will affect oil pressure but I'm not sure where it is. The guy telling me about it has and 05 and his pressure went way down and all they did was replace this valve or what ever it was.

Greg

Greg

Excess oil pressure is un needed. Even a fully rebuilt engine here with exacting oil clearances on everything will run on the low side of the gauge and thats perfect. We only need to lubricate, not saturate. Excess is drag and windage. Street or Strip dont matter.

There is a tradeoff. With higher RPMs you need more flow to keep the bearings wet. The additional load on the bearings and the rotation of the journals kicks the oil out at an ever increasing rate. Being a fluid system, you need to increase the pressure to overcome parasitic restriction in the system.

I seem to remember you wanted at least 10-14 PSI per 1000 RPM on gas engines. Diesels, with the tighter rev range, might need a pinch more.

Back on topic, I don't know that you will get more pressure out of the stock oil pump. At operating temps, the bypass is closed and the engine is getting full flow from the pump. It would take a higher flowing pump to get pressures higher when the oil is hot. An oil cooler would be one way to get pressures back up. Cooling effectively reduces the rate that the bearings eject oil.

I WANT MORE PRESSURE!!iwant 60psi at 2000 rpm and im going to do whatever it takes to get it.

If Eric says you dont need more pressure, theres a good chance you dont need more pressure...

applying "gut feelings" of what the engine "needs/should have" does not always work... Yeah, my trucks oil pressure "SEEMS" low to me too, but its within GM's minimum specs, and Eric says its fine so thats enouhg to make me not worry. GM designed the engine, not me. JMO

ben

they designed the lb7 with 60 psi at 2000.and the lly with 40.so which motor did they screw up on??

If Eric says you dont need more pressure, theres a good chance you dont need more pressure...

applying "gut feelings" of what the engine "needs/should have" does not always work... Yeah, my trucks oil pressure "SEEMS" low to me too, but its within GM's minimum specs, and Eric says its fine so thats enouhg to make me not worry. GM designed the engine, not me. JMO

ben
did i say i needed more pressure,no.i said i wanted more pressure.im the customer give me what i want!!argghhh.lol.iwanted more power,so i bought more power.i wanted bigger tires so i got bigger tires.i want more oil pressure so give it to me.ahahahh:D

Get the Lucas! Cheapest easiest way. The oil gets way too hot in some circumstances and eats away at pressure.

i want more oil pressure so give it to me.ahahahh:D

but maybe its not what the engine wants.

id rather have the engine getting what it wants, not what I want for it.

did i say i needed more pressure,no.i said i wanted more pressure.

so, why do you want it if you dont need it? :confused:

ohh please.you think the engine wants to turn bigger tires or run the 1/4 in 12 sec.or pull 34000 lbs loads.these trucks have always been about what we want.we dont care what the dealer wanted for our trucks,we dont care what gm wanted for our trucks.it has always been about what we wanted.so give it to me now!!!more oil pressure now!!):h how come when i start a thread somebody always wants to know why i want something?or argue about it.i want what i want just like anbody else.it dosent matter why i want it,i just want it.

Seriously, get a modest size engine oil cooler with a thermostatic bypass. Otherwise you will have to find a bigger oil pump.

maybe i can hook up some kind of dry sump system??ooh then i could add capacity,maybe an xtra gallon or 2.

Just crimp one of the lines, oil pressure will go way up!! LOL

I have always thought the lly had low pressure myself.

I was going to recommend an oil treatment until I read this

http://skepdic.com/slick50.html and this

http://www.ftc.gov/opa/1997/10/valve.htm

Stuff like this is what makes me super sensitive to manufacturer's claims..

Good luck with your quest!

As I stated earlier if you need and additive you need to change to a good oil . Good oils do not need additives. The only good thing about Lucas is they no how to market the product and theirs a hugh margin for the retailer.

Greg

As I stated earlier if you need and additive you need to change to a good oil . Good oils do not need additives. The only good thing about Lucas is they no how to market the product and theirs a hugh margin for the retailer.

GregI gotta side with ya on this one Greg:ro)

How do you disagree with the "masters." All good points. I'm not a Lucas salesman, nor did I want to Hijack the thread and turn it in to a promotion. He wants more oil pressure, this stuff will give it to him. It does what it says it will do, does no damage that I'm aware of in close to 1/2 million miles on 2 D/A trucks of mine. I was once in his shoes. Heavy towing in hot weather does cruel things to duramax oil, it can be a mind bender to see 20 psi oil pressure at 65 mph pulling a large 5th wheel! Maybe that's ok, I was never comfortable with it. For $20 a gallon, it was worth the peace of mind for me.

How do you disagree with the "masters." All good points. I'm not a Lucas salesman, nor did I want to Hijack the thread and turn it in to a promotion. He wants more oil pressure, this stuff will give it to him. It does what it says it will do, does no damage that I'm aware of in close to 1/2 million miles on 2 D/A trucks of mine. I was once in his shoes. Heavy towing in hot weather does cruel things to duramax oil, it can be a mind bender to see 20 psi oil pressure at 65 mph pulling a large 5th wheel! Maybe that's ok, I was never comfortable with it. For $20 a gallon, it was worth the peace of mind for me.

Look at it this way if it raised to oil pressure all that means is its harder to pump. Does not really mean that you have any more flow to the bearings. Pump wet cement through a pumper and then dry it up a bit and you will see the results. It pumps a lot harder but you don't get anymore cement out the other end. People also get alarmed when they switch toi a sysnthetic because sometimes the pressure will drop a bit, its just pumping easier. The oil pump is a positive displacement pump and will pump x amount reguardless.

Greg

Dude, I think you need help... I am no expert in fluidity or hydro-carbon circulation, but I have built a few high performance sand cars in my day and believe that higher pressures in the oil robs HP, and means that the sticky stuff is harder to move around and get in the places it needs to be for proper lubricity.

Oh and I live by "If it aint broke, don't fix it"

I haul a 40 foot toyhauler loaded with quads and a sand car in 120 degree weather, my truck's oil pressure has not changed since I bought it and it IS much lower than the Corvette engine in my sand car, but that is comparing apples to soybeans.....

jmho.

Look at it this way if it raised to oil pressure all that means is its harder to pump. Does not really mean that you have any more flow to the bearings.

:exactly: excellent point Greg.

ben

Dmaxitol , I never argue with a man that hunts with big guns like that one you have.

Hmmm, maybe GM has a reflash that will make the pressure gauge lie.

Dmaxitol , I never argue with a man that hunts with big guns like that one you have. Awe, That was just a weekend pleasure trip to Irac!:ro)

GM over the years has lowered the oil pressure on the Duramax. IIRC the 03 was the first year the pressure was lowered after a lot of testing. It does hurt mileage and performance. This was part of the reason GM lowered it. At this time engine manufacturers are looking at a new pump system that has a variable pressure output depending on the rpm of the engine. This was said to increase mileage a few percent.

GM over the years has lowered the oil pressure on the Duramax. IIRC the 03 was the first year the pressure was lowered after a lot of testing. It does hurt mileage and performance. This was part of the reason GM lowered it. At this time engine manufacturers are looking at a new pump system that has a variable pressure output depending on the rpm of the engine. This was said to increase mileage a few percent.
the question is how did they do it?the part number is the same for lb7 and lly.but they do not carry the same pressure.what is different?

I for one can testify that lowering the oil pressure to improve MPG, if indeed it actually was, didn't help! I believe it was another "gauge trick." My '01 got 25 mpg on the highway, the '03 averaged 23 mpg, the '04.5 is lucky to see 18! Oil pressure has very little to do with MPG on our trucks! I've tried them all, brands,viscosities and additives. Dino and syn.! Very little differance.:rolleyes:

Just out of curiosity, what is normal oil pressure for an LLY? When my truck is at an idol it is about 28 psi. It sure seems like this is low to me. Is this normal pressure for the LLY?

Thanks

The factory gauge lies. Using EFI to look at the real signal, mine is typically 14 PSI at idle hot. (normal operating temp) Running down the highway, usually 35 - 45 PSI. As the engine works harder and get hotter, the pressure will drop, but I have not paid close attention. I will log it the next time I pull the trailer.

Expect to see thinner oils mandated by the OEMs in the future, lots more Zero weights, just one way to increase mpg and efficiency in new motors.

The factory gauge lies. Using EFI to look at the real signal, mine is typically 14 PSI at idle hot. (normal operating temp) Running down the highway, usually 35 - 45 PSI. As the engine works harder and get hotter, the pressure will drop, but I have not paid close attention. I will log it the next time I pull the trailer.

wow fingers thats low...14psi is the MINIMUM spec at idle isnt it?

Tuesday was VERY hot here (95*+), I was towing for parts of the day, truck was working pretty hard, ECT never moved, trans was just barely a tick over 200, but oil pressure hot at idle (according to the Tech 2/EFILive) was 22psi. Cruising on the highway I didnt check it on the data bus, but the guage always reads 60psi or above. This is with Rotella 5-40 synthetic...

I thought the oil supply to the underside of the piston was shut off at 35 psi. That would kill an already super hot piston to lose its oil bath.:eek:

I thought the oil supply to the underside of the piston was shut off at 35 psi. That would kill an already super hot piston to lose its oil bath.:eek:

Book says 14 PSI minimum at idle, 42 PSI at 1800 RPM. Under piston jets open at 29 PSI. FWIW

I use Rotella 15w40. If that makes a difference. I think Rick uses it too as does Sideswiper. I'll check it again the next time I go out.

would the 5-40 syn versus 15-40 dyno make that big a difference in psi?

would the 5-40 syn versus 15-40 dyno make that big a difference in psi?

It could because the synthetic pumps easier. The best thing to do is drive it and don't worry about it unless it goes way low. Its the volume you of oil and the pump will pump the same volume if it is a synthetic or dino oil but pressure can be a bit less with synthetic.

Greg

Greg is right. You don't need any more than about 10 psi per 1000 rpm. Higher pressure after that just means your engine is having to work harder than necessary to achieve the required flow, which wastes energy and hurts fuel economy.

Flow is the key. More flow = more lubrication and better cooling. If you're foolish enough to ONLY want higher oil pressure, just run straight 50 weight oil and you'll see an amazing jump in pressure, but you're not doing your engine any favors. In fact, just the opposite is true. Oil experts will correctly tell you to run the thinnest oil possible that will still give you a minimum of 10 psi per 1000 rpm, and that meets your engine's API rating requirements.

I'm running Amsoil HDD (Heavy Duty Diesel) 5w-30 synthetic. My pressure dropped a little, but is still more than adequate. This indicates that I'm getting all the flow I need, but the engine is working less hard to provide that flow.

Before flaming, please do a google search for a series of oil articles by A. E. Haas, a world renowned oil researcher and expert. :cool:

You guys may be missing my point, or I may be missing yours.:)

If the nozzles cooling the bottom of the pistons shut off below 29 psi, and I am towing heavy with a ton on egt and ect, and my oil pressure drops below 29 psi then I have lost a ton of protection at the worst possible time. If I can keep the pressure above 29 psi at all times then all 8 of my pistons survive and stay with me.:)

If the nozzles shut off at 29psi, they're probably off a lot of the time at idle or low rpms. Sounds like a good reason to keep rpm's up when towing up a hill......:)

I think GM was worried about high cold pressure. There are several things too high pressure can do and none are good. You mentioned that the pumps both have the same number. Do the pumps come with the drive gear? If not that could be where the difference pressure comes from. Our pumps are positive displacement and variable volume. GM could have decreased the pressure in any number of ways. Pumping up pressure with an additive is messing with the viscosity. The oil manufactures do a lot of engineering with viscosity modifiers to insure we have proper flow from -10 to 105F. Later! Frank

You guys may be missing my point, or I may be missing yours.:)

If the nozzles cooling the bottom of the pistons shut off below 29 psi, and I am towing heavy with a ton on egt and ect, and my oil pressure drops below 29 psi then I have lost a ton of protection at the worst possible time. If I can keep the pressure above 29 psi at all times then all 8 of my pistons survive and stay with me.:)

Rick
Anytime I am off idle I have at least 40psi. If you are dropping below the 29psi with anything less more than just and idle I would have to say something is wrong.

Greg

If the LLY and LB7 have the same part number it is probably because the LLY superceded the LB7, GM won't keep seperate part numbers if the later one will work in place of the older one.
You could always put in a good used LB7 pump to test your therory.
IMHO, Merle

You guys may be missing my point, or I may be missing yours.:)

If the nozzles cooling the bottom of the pistons shut off below 29 psi, and I am towing heavy with a ton on egt and ect, and my oil pressure drops below 29 psi then I have lost a ton of protection at the worst possible time. If I can keep the pressure above 29 psi at all times then all 8 of my pistons survive and stay with me.:) I don't know if that the statement that the nozzles are shut off is a good explanation of what happens. the thresh hold pressure for the nozzles to operate at peak output is 29psi. meaning that the pressure needed to squirt the appropriate amount of oil to the pistons is obtained at 29psi. there is no physical valve that shuts the nozzles down and the pistons will still receive oil just not as much as if the nozzles were under 29psi of pressure. my worry would be about cylinder wall lubrication and not so much cooling as the pistons will cool fairly fast with the smaller charge of fuel being shoot at them on idle and the roughly the same amount of air charge being moved past them. as long as there is no combustion or at least little to no combustion the pistons will dissipate heat quickly. the ects are at 200deg and the air charge at 200deg this will do wonders to cool off pistons. no oil needed for cooling at these times.

Just went to the garage to double check. Each nozzle has it's own little pop off valve integrated into the bolt. The bolt holds the nozzle assembly in similar to a banjo fitting with the oil flowing though the bolt into the nozzle assembly. So yes, they shut off below about 29 PSI.

Fingers is correct. I dont know if its exactly at 29 lbs, but its darn close, regardless of what the spec says

Just went to the garage to double check. Each nozzle has it's own little pop off valve integrated into the bolt. The bolt holds the nozzle assembly in similar to a banjo fitting with the oil flowing though the bolt into the nozzle assembly. So yes, they shut off below about 29 PSI.never looked at the jets themselves, thanks for the info. it interests me to know how the cylinder walls get lubrication at idle. are there squirt holes in the con rods? or dose GM just rely on the rod bearings slopping off enough oil to sling it to the bottom of the piston?