PRESSURE is a measure of RESISTANCE to FLOW
thicker or higher viscosity oils tend to RESIST the flow thru smaller clearances untill they warm up and the viscosity tends to drop off.
as long as the oil pressure stays above about 20 psi at idle and below about 80psi your NORMAL and should have no problems, but THINNER viscosity oils pump faster and reach the parts faster on start up where much of an engines WEAR occures, WITH SYNTHETIC OILS,THICKER oils DON,T, provide a big increase in protection as the FILM STRENGTH is similar, remember the object is to prevent DIRRECT mechanical contact thru having a FILM of oil under pressure BETWEEN the moving surfaces, the oils viscosity has little effect AS LONG AS its sufficiant to form that barrier FILM, and ABSORB AND CARRY AWAY HEAT,DEBRIE,(CRUD) from the bearing surfaces. modern synthetics DON,T THIN OUT under heat to nearly the same extent as mineral base oils did so thinner 5w30 and 10w30 can protect parts as well or better than 10w40,20w50mineral base oils that thinned out under high heat conditions
keep in mind the CLEARANCE between moving parts determines in part the load rates the oil film can support, as an engine wears it tends to have increased clearances so the resistance to flow drops slowly with wear.
if you want some further info, read thru these
http://www.bobistheoilguy.com/
http://www.performanceoiltechnology.com/tenmythsaboutsyntheticlubrication.htm
http://www.oil-tech.com/motoroil-comparison.htm
http://www.micapeak.com/info/oiled.html
http://minimopar.knizefamily.net/oilfilterstudy.html
most comon question I get? "will a high volume oil pump help or hurt my engine?"
followed by some guy saying
"If you're using a stock capacity pan, the high volume oil pump could actually suck out all the oil from the pan before it is drained back in, thus creating bad, bad problems"
absolutely proven false bye SMOKE YUNICK with HIGH SPEED PHOTOGRATPHY and CLEAR WINDOWS IN ROCKER COVERS AND OIL PANbut what can and does happen is the oil pump pickup can and does get mounted or moved too high or low in the oil pan,restricting access to the oil supply, sometimes the pickup comes loose or under hard acceleration or brakeing the oil in a non-baffled pan can rush away from the pickup under (G) forces, this is not pumping the pan dry, a baffled pan with a windage screen with the same oil supply volume would work perfectly
ok lets look at a few things, pressure is the result of a resistance to flow , no matter how much oil is put out by the oil pump there is almost no pressure unless there is a resistance to that oil flow and the main resistance is from oil trying to flow through the bearing surface clearances and once the pumps output pressure exceeds the engines ability to accept the oilflow at the max pressure the oil return system/bypass spring allows the oil circles back through the pump ,now the amount of oil flow necessary to reach the furthest parts in the engine from the oil pump does not go up in direct relation to rpm, but it instead increases with rpm at a steadly increaseing rate that increases faster than the engine rpm due to centrifugal force draining the oil from the rods as they swing faster and faster since energy increases with the square of the velocity the rate of oil use goes up quite a bit faster due to the greatly increased (G-FORCES) pulling oil from the rod bearings over 5000rpm going to 8000rpm than the rate of oil flow increases from 2000 rpm to 5000rpm (the same 3000rpm spread) and remember the often stated (10 lbs per 1000rpm)needs to be measured at the furthest rod and main bearing from the pump not at the pump itself, next lets look at the oil flow itself, you have about 5-6 quarts in an average small block now the valve covers never get and hold more than about 1/3 to 2/3 of a quart each even at 8000 rpm (high speed photography by SMOKEY YUNICK doing stock car engine research with clear plastic valve covers prove that from what Ive read) theres about 1 quart in the lifter gallery at max and theres about 1 quart in the filter and in the oil passages in the block, that leaves at least 2 quarts in the pan at all times and for those that want to tell me about oil wrapped around the crankshaft at high rpms try squirting oil on a spinning surface doing even 2000rpm (yes thats right its thrown off as fast as it hits by centrifugal force, yes its possiable for the crankshaft WITHOUT A WINDAGE SCREEN to keep acting like a propeler and pulling oil around with it in the crank case but thats what the wrap around style milodon type windage screen is designed to stop)the only way to run out of oil is to start with less than 4 quarts or to plug the oil return passages in the lifter gallery with sludge or gasket material! now add a good windage tray and a crank scrapper and almost all the oil is returned to the sump as it enters the area of the spinning crankshaft! forming a more or less endless supply to the oil pump, BTW almost all pro teams now use DRY SUMP SYSTEMS WITH POSITIVE DISPLACEMENT GERATOR PUMPS that are 3,4,or 5 stage pumps each section of which has more voluum than a standard voluum oil pump because its been found total oil control is necessary at high rpms to keep bearings cool and lubed
NOW I POSTED THIS BEFORE BUT IT NEEDs REPEATING
ok look at it this way,what your trying to do here is keep an pressureized oil film on the surface of all the bearings to lube and cool them and have enough oil spraying from the rod and main bearing clearances to lube the cam and cylinder walls/rings. now a standard pump does a good job up to 5000rpm and 400 hp but above 6000rpm and 400hp the bearings are under more stress and need more oilflow to cool and because the pressure on the bearings is greater you need higher pressures to maintain that oilfilm.lets look at the flow verus pressure curve. keep this in mind, good oil flow volume across the bearing surfaces to cool and luberacate them and to provide a boundry layer between the metal surfaces is more important than the pressure reached at all rpms. since oil is a liquid its non-compressable and flow will increase with rpm up to the point where the bypass circuit starts to re-route the excess flow at the point were the pressure exceeds the bypass spring pressure. but the voluum will be equal to the pumps sweep voluum times the rpm of the pump, since the high voluum pump has a sweep voluum 1.3-1.5 times the standard pump voluum it will push 1.3-1.5 times the voluum of oil up to the bypass cicuit cut in point,that means that since the engine bearings leakage rate increases faster as the rpms increase because the clearances don,t change but the bleed off rate does that the amount of oil and the pressure that it is under will increase faster and reach the bypass circuit pressure faster with the high voluum pump. the advantage here is that the metal parts MUST be floated on that oil film to keep the metal parts from touching/wearing and the more leakage points the oil flows by the less the voluum of oil thats available for each leakage point beyond it and as the oil heats up it becomes easier to push through the clearences.now as the rpms and cylinder preasures increase in your goal to add power the loads trying to squeeze that oil out of those clearances also increase. ALL mods that increase power either increase rpms,cylinder preasures or reduce friction or mechanical losses. there are many oil leakage points(100) in a standard chevy engine.
16 lifter to push rod points
16 pushrod to rocker arm points
32 lifter bores 16 x 2 ends
10 main bearing edges
9 cam bearing edges
16 rod bearing edges
2 distributor shaft leaks
1 distributor shaft to shim above the cam gear(some engines that have an oil pressure feed distributor shaft bearing.)
so the more oil voluum the better.chevy did an excelent job in the design but as the stresses increase the cooling voluum of the extra oil available from the larger pump helps to prevent lubracation delivery failure,
do you need a better pump below 5000rpm or 400hp (hell no! at that level the stock pump works fine) above that level the extra oil will definitely helppossiable deficient oil flow and bearing cooling and a simple increase in pressure does not provide a big increase in voluum that may be necessary to keep that oil film in the correct places at the correct voluum at all times.the stock system was designed for a 265cid engine in a passenger car turning a max of about 6000 rpm but only haveing the stress of under 300hp transmitted to the bearings, Im sure the orriginal designers never thought that the sbc or bbc would someday be asked to on occasion hold up to 450-800hp and 6000-8000 rpm.nore did they forsee valvesprings that placed sometimes as much as 500lbs and up loads on the lifters and the use of over 9 to 1 compression ratios in the original design so the oil voluums and pressures necessary to cool those valve springs and bearings at those stress levels were never taken into account for that either , the stock pump works but was never designed for the loads and rpms that a modern engine hotrodded to over 450hp sees
the standard volume pump gears are about 1.2" long the high volume pump gears are about 1.5 inches long (depends on manufacturer)
heres the discriptions right from chevy
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
14044872
SBC Oil Pump, High-Volume. This high-volume pump has
1.50" long gears.It has approximately 25% more capacity than a production pump at standard pressure. Does not include screen.
and yes I comonly build small blocks useing bbc oil pumps like the ls7 pump, it has
1.3" gears but they are bigger in dia. and have 12 not 7 teethlike the small block pumps (many standard sbc pickups use 5/8" dia. pickups) (the ls7 pump is best used on 8qt-9qt road racing oilpans as the larger 3/4" pickup flows lots of oil for extreme high rpm engines with a multi baffled pan useing windage screens, scrappers and cut outs for extreme (G) loads where a dry sump can,t be used or cost makes you stick to a wet sump pan.
these LS7 pumps dont fit most sbc oil pans so your stuck using the high volume sbc oil pump if your not using a true racing 8-9 qt style oil pan in some cases
