rustytoolss
Well-Known Member
Will using full groove main bearing lower your oil pressure ? If so how much ballpark ?
full groove main bearings oil pressure ?
- Thread starter rustytoolss
- Start date
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BigBlockMopar
BigBlockMember
I've installed FG bearings in a few engines but this was usually also done with other items like needle bearinged rockers, or in older engines it was just to make sure the (old) rod bearings got more life out of them.
If I were to guess I think it would drop the pressure about 5-10psi on a hot engine perhaps.
If I were to guess I think it would drop the pressure about 5-10psi on a hot engine perhaps.
rustytoolss
Well-Known Member
I replaced my rod bearings, full groove mains (clearance .0015 each) new standard oil pump, new cam and lifters ( no cam bearings) I'm getting about 52 psi cold, and around 12-15 hot idle with 10w30... I'm not as happy as I was hoping:sad10:
EL5DEMON340
Well-Known Member
I think they make a 3/4 groove
rustytoolss
Well-Known Member
will a high volume pump help ?
So what's wrong with that?
BigBlockMopar
BigBlockMember
For me, any pressure below 20-psi is 'worrying'.
The cambearings could still be the cause of the low hot oil pressure.
More oil volume could help keeping the pressure up a bit.
Or change to a 10w40 oil perhaps.
The cambearings could still be the cause of the low hot oil pressure.
More oil volume could help keeping the pressure up a bit.
Or change to a 10w40 oil perhaps.
rustytoolss
Well-Known Member
I agree ..under 20 is scary. I will probably put in a HV pump. I guess I could even go 20W50.
805moparkid
Slant and AFX Guy
THIS, i will be using these on my next build
71Scamper
Mopar runs thru my veins!
Take a look at this sticky:
http://www.forabodiesonly.com/mopar/showthread.php?t=103623
To support the full groove bearing with proper flow and pressure you need to clean up the supply passages as well as run an HV oil pump with a pan that can hold at least 6 quarts of oil. I've also done the mods mentioned in this sticky, as well as removing all the casting flash, to allow for faster return flow. Although I haven't run my engine yet, I'm confident this will greatly improve the life and durability of my 340. I'm sure these mods are good across the board for small blocks.
Absolutely ZERO wrong with 10 PSI at idle with a stock volume pump. NOTHIN, NADA, ZILCH. You ever tried to hold back 10 PSI on something with your thumb? That's enough to slobber oil ALL OVER the inside of that engine. Some of yall need to worry about important stuff.
Why not put the high pressure relief spring in the oil pump?
Whether you run a stock or HV.
You are having a problem with PRESSURE, not VOLUME. It makes more sense to use a high pressure spring to increase your pressure versus trying to throw more volume at it. However, It wouldn't hurt to go with the high volume oil pump AND the high pressure spring.
I've ran the high volume Mellings pumps with the high pressure spring for years and hundreds of thousands of miles without any problems on daily drivers with stock 5 quart oil pans.
Whether you run a stock or HV.
You are having a problem with PRESSURE, not VOLUME. It makes more sense to use a high pressure spring to increase your pressure versus trying to throw more volume at it. However, It wouldn't hurt to go with the high volume oil pump AND the high pressure spring.
I've ran the high volume Mellings pumps with the high pressure spring for years and hundreds of thousands of miles without any problems on daily drivers with stock 5 quart oil pans.
Those mods are good, but I feel that they are overkill on a street engine. IF you are going racing, then I would use some of them.
Opening up your passages will REDUCE your oil pressure. Pressure is force over area [pressure = (force/area)]. So if you increase the area, you lower the pressure.
Simple engineering... If you have a surface that is wearing under a force, you increase the area to reduce the net force per unit area. :read2:
fishy68
Tyr Fryr's Inc.
I totally agree. I have seen several engines in work trucks run for hundred's of thousands of miles with less than 10 psi at idle and 30 psi at full throttle. Very few cars will tax the engine like a work truck does. I used to subscribe to the theory that you had to have a bunch of oil pressure when I was young and didn't know as much but I learned on an old 360 that only held 10 psi at idle and 45 wide open and ran the crap out of it for years running low 13 second 1/4's that you don't really need a bunch of oil pressure.
The mods Guitar Jones described are great for a race car, or even a super hot street/strip car but for the normal street car are overkill IMO. Like Krazykuda said opening up the passages can lower your oil pressure. You need a good HV pump and larger pickup and more capacity for those mods to properly work.
If you really want more oil pressure up the oil grade to 10w40 or 15w40. That should give you nearly 10 psi more
Keep this in mind also. The more you pressurize oil the hotter the oil gets. The purpose of oiling the bearings is to lubricate and cool them. If your making it hotter how is it going to cool as good?
rustytoolss
Well-Known Member
I put a different gauge on it, and am showing 17-20 psi hot, so after what has been posted. I will drive an see how thing go. Thanks guys
nm9stheham
Well-Known Member
Yes, I would not worry over that level. And note that pressure increases will tend to pump more oil to the heads, and at high RPM's, can pump so much to the heads that the pan level gets low; going around curve under those conditions can leave the pump sucking air for a moment. So high pressure has to be done with some caution and knowledge of where the oil will go.
Use a good qualiity oil and you will be fine. With a full synthetic (after break-in), you will never see an issue.
Use a good qualiity oil and you will be fine. With a full synthetic (after break-in), you will never see an issue.
rustytoolss
Well-Known Member
Don't have a tach on it yet.
nuttyprof
Well-Known Member
If you put a high pressure spring in it that will NOT help IDLE pressure. The pressure relief is not open at that flow rate, the relief is only there to limit MAX oil pressure. To increase idle pressure you need to increase oil flow, that is why the pressure goes up as rpm goes up. a high volume pump will increase pressure at idle but increase load on the pump drive, add to the possibility of aeration of the oil ( as it sprays from the pressure relief ) add heat to the oil, etc. I've always heard 10 psi per 1000 rpm up to 50-60 psi was good, I do not claim to know for sure on that but I would not worry about 12-15 at idle. Cleaning out the restrictions in the oil passages should not lower the oil pressure unless they were restricted before you cleaned them. Oil pressure is a function of the oil flow into the system vs oil flow out, and viscosity, period. The clearance on the bearings is specified to allow adequate oil in and a certain amount of oil out ( to cool the bearing). If the clearance is to great then you will have an oil pressure "leak" that can only be fixed by reducing the "leak" or increasing the flow. If the pressure comes up to over 50 psi before you get to 5000 rpm and stays above 10 at idle I'd be happy. Full groove bearings should not lower oil pressure if the clearances down stream are good. It would reduce restriction at the crank but if cam bearings are good and lifter clearance in there bores is good should be no problem.
moper
Well-Known Member
71Scamper
Mopar runs thru my veins!
The reason he's having an issue with pressure is because he doesn't have enough volume to support the natural oil leaks inside the engine which in turn caused a low oil condition. Increased oil volume should increase the pressure also. Remember pressure is the result of restriction in the oil system.
Simple engineering... if you have too low of pressure because your pump can't put out the proper volume of oil to compensate for the larger "internal oil leaks" then your pressure is going to go to crap.
Yes opening passages will reduce pressure because you reduced the amount of restriction in the oil system, in turn supplying more oil to key critical areas. in order to support the reduced restriction in the oil system, you will need to run an HV pump.
Here's something to ponder upon: If you opened up the oil passages in your oil system but left the openings alone in the bearings, and you have a reduction in oil pressure, what does this tell you? The restriction was the supply line the whole time, and the bearings can support more oil flow (volume). Who in their right mind would not want more protection for the engines critical areas (main/rod/cam bearing)????
^^^Exactly!^^^
Theoretically, yes. But no, not for me. I built one engine that way, never again.
Restrictions will REDUCE oil flow while increasing the pressure. A high pressure spring will INCREASE the flow along with the pressure.
If he his larger "internal oil leaks" then he should fix those. You don't replace your water pipes in your house with larger diameter pipes to compensate for a hole in your garden hose to overcome the loss due to the leak, you fix the hole or replace the hose....
The thread on increasing the oil passages is great, but not necessary for a street engine. They are only necessary for a racing engine. Some of those mods are a little above the capabilities of the average weekend hobbiest/enthusiast.
The automotive manufacturers go through many hours of testing to prove the engines are capable for the public to use before ever making them available to the masses. Bench testing, dyno testing, and proving grounds testing, not to mention road trips to areas with extreme conditions (hot/cold) to prove out the design. Each component supplier also doing the testing on each of their parts involved also. Have you seen the pictures of the engines on the dynos at Highland Park that were run at wide open throttle for HOURS and the exhaust manifolds are glowing orange they are so hot! The 'standard' passages will work fine for street engines.
Now your last paragraph on opening up the oil holes and the bearings being able to handle the extra flow is diving way too deep. The oil flow for the main, rod, and cam bearings is limited by the radial clearance. If you increase your radial clearance to try to get more oil flow through, the clearances will be too great. The engine will knock due to the excessive clearances and you will wipe out your bearings and mating components. Do a little research on "Boundry Layer Lubrication" which is how your lubrication on bearings works, it's part of Fluid Mechanics. It explains how the oil can support the load on the bearings and prevent the metal to metal contact that creates wear (shear). Too much clearance won't allow the fluid to support the load and you will get metal to metal contact which will destroy your engine. It's based on the old hydraulic thing where you can compress air, but not a liquid/fluid.... You have to APPLY the laws of physics, you can't break/change them (trying to do so may result in personal injury up to and including death)...
All of my engines get the high volume pump with the high pressure spring. Some people argue that you do not need the high volume pump, but I would rather have it myself.
moper
Well-Known Member
Here's a very good article:
http://nzetc.victoria.ac.nz/tm/scholarly/tei-Gov04_02Rail-t1-body-d22.html
I think you might be confused about boundary layer lubrication... Internal combustion engines use hydrodynamic lubrication because the oil is the load bearing member and the development of the oil wedge is dependant on the rotational motion. With boundary layer the surfaces are the load bearing members. Least that's how I understand it.
Also in regard to having high indicated pressures... The oil pressure tap is off the lifter galley in smallblock Mopars. If you are pumping a ton of oil into the system, you are not reading what the mains are seeing. You're reading what the lifters are seeing and hoping that this indicates the mains and rods are getting enough. If the passages to the mains are left at factory size, you are not "seeing" the bearing clearance in that reading because you're pumping so much oil into the galley. Pressure is resistance to flow and what it indicates can be doublesided. You have to make sure that the higher indicated pressure isn't resistance caused by passages that are too small or too much of a volume entering the system. Otherwiase you're using a bit of power to make a bunch of heat.
http://nzetc.victoria.ac.nz/tm/scholarly/tei-Gov04_02Rail-t1-body-d22.html
I think you might be confused about boundary layer lubrication... Internal combustion engines use hydrodynamic lubrication because the oil is the load bearing member and the development of the oil wedge is dependant on the rotational motion. With boundary layer the surfaces are the load bearing members. Least that's how I understand it.
Also in regard to having high indicated pressures... The oil pressure tap is off the lifter galley in smallblock Mopars. If you are pumping a ton of oil into the system, you are not reading what the mains are seeing. You're reading what the lifters are seeing and hoping that this indicates the mains and rods are getting enough. If the passages to the mains are left at factory size, you are not "seeing" the bearing clearance in that reading because you're pumping so much oil into the galley. Pressure is resistance to flow and what it indicates can be doublesided. You have to make sure that the higher indicated pressure isn't resistance caused by passages that are too small or too much of a volume entering the system. Otherwiase you're using a bit of power to make a bunch of heat.
Boundary layer lubrication is the main principle behind hydrodynamic lubrication. It is the ability of the fluid to support the load and keep the two moving surfaces from contacting each other and causing shear. With too much clearance, the fluid cannot support the load and moves out of the way to allow metal to metal contact and shear wear. Hydrodynamic lubrication is boundary layer lubrication with a fluid supply (on steroids).
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