bearings and oil flow

Discussion in 'Oil and Lube Systems' started by grumpyvette, Sep 19, 2008.

  1. grumpyvette

    grumpyvette Administrator Staff Member

    Bearings and oil flow

    viewtopic.php?f=53&t=88 ... cation.htm

    keep in mind both engine oil temps and trans fluid temps seldom reach operational temps,fluid
    and stabilize , for semi consistent data,in under 12-15 minutes of drive time,temps have a huge effect on lubricant viscosity and durability. . ... stall.html
    Id also point out that, if you properly set up an engine's oil system, open the oil drain holes and use the proper oil pan, windage screen and crank scraper, its virtually impossible , in a well designed engine to run the engine "long enough to pump all the oil upstairs."
    as with a properly designed baffled oil pan, with a carefully fitted and clearanced windage screen and crank scraper, the oil pump simply reaches a flow rate pumping oil out of about 100 or so potential lubricant flow leakage points

    theres zero doubt an accusump oil feed is a good insurance policy to maintain oil pressure at the bearings, but simply having a 7-8 quart baffled oil pan,properly clearanced, windage screen and crank scraper will insure the oil pressure remains consistent , mostly due to the fact that theres always going to be enough oil over the oil pump pick-up, simply because theres really no room to pack most of the available oil volume in the upper engine ,plus the fact that hot oil flows well.
    OIL PRESSURE read on the oil pressure gauge is a MEASURE of RESISTANCE to oil flow, you can REDUCE the pressure the gauge reads by either increasing the engine clearances or REDUCING the oil viscosity (thickness) so it flows thru the clearances faster with less resistance.(OR INSTALLING A SLIGHTLY WEAKER OIL PUMP BYE_PASS SPRING,that limits the pump pressure before it allows some oil to re-circulate back through the bye-pass valve ,from the high pressure back to the low pressure side of the pump impellers, but only the max pressure you reach is limited by the bye-pass spring,in your oil pressure bye pass circuit and its that spring resistance determines the point where the bye-pass circuit, opens and limits max oil pressure, but the bye-pass circuit has zero to do with anything else, if its functioning correctly,
    there are many oil leakage points(100) in a standard Chevy engine.
    16 lifter to push rod points
    16 push rod 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.)
    once oil exits the bearings or valve train it flows mostly by gravity back to the oil pan sump, but a properly designed windage screen and crank scraper correctly clearanced allows the spinning crank/rotating assembly to act like a directional pump that drags the vast majority of the oil flow back to the sump, by design.

    from chevy high performance mag




    with the engine up to operational temp.of between about 180f-210f
    and using an oil viscosity that maintains at least 15-20 psi at hot idle in traffic,
    your engine should maintain a MINIMUM of 10 psi per 1000rpm and max out pressure at about 4500-5500rpm at 60psi or higher
    remember the thicker the oil the harder it is to force thru the clearances in the engine, and pressure is how you measure the RESISTANCE to oil flow, but you should use an oil viscosity that at least maintains that 15-20 psi at idle

    one factor thats frequently over looked is that many bearing manufacturers don,t seem to have placed the bearing oil feed holes in bearing shells so they exactly match the oil feed passages in the engine blocks
    example heres a common minor mis-match on the bearing shell/oil passage alignment

    but Ive seen some where over 1/3-to-1/2 the oil feed hole was blocked due to misalignment, thats usually easily cured, by drilling a shallow increased diameter recess in the blocks oil passage to open it to match the bearing or opening up the bearing feed hole, but which ever route you take be sure to carefully clean and deburr both

    increasing the groove, from 180 deg to 270 deg, lowers bearing support, increases oil flow rates and tends to increase wear


    As you'll see in Figure 1, below two different types of grooved upper main bearing shells

    the oil groove terminates before it gets to the bearing parting line. This style of main bearing has accounted for a 15 percent or more increase in hot idle oil pressure. So if you're looking to eliminate some of those unexplained low oil pressure gremlins contact your bearing manufacturer and ask about this style bearing and availability for the engine applications that you are building.

    keep in mind only the upper main bearing shell should have an oil groove, having a 360 degree oil groove lowers the bearing ability to handle high rpm loads

    The main bearing oil groove is required for the sole purpose of supplying oil to the
    connecting rod big end bearing. At one time it was common to have a full 360° groove on the
    main bearing to provide an uninterrupted supply of oil to the big end by means of a single
    drilling from the main journal. This was achieved by having identical upper and lower bearing
    As bearing loads increased this design proved unsustainable as the oil film thickness, on
    which every crankshaft bearing relies, became insufficient for reliable main bearing
    operation. The solution was to increase the bearing area on the more heavily loaded lowerhalf
    bearing by reducing the extent of the groove to around 230° or even 180° in order to
    provide a single bearing land of greater width. Any increase in bearing width enables a
    higher oil film pressure to be sustained as the distance from the centre of the bearing to the
    edges, which cannot sustain an oil pressure, is increased. This in effect allows the
    generation of a thicker oil film with which to separate the shaft and bearing shell.
    The reduced oil groove extent would sometimes be compensated by a cross-drilling on the
    main journal in an attempt to maintain an uninterrupted supply of oil to the big end bearing.
    However, in many cases it was found that the big end could cope very well with the
    subsequent intermittent oil flow offered by a single drilling from a 180° groove.
    Nowadays, with the use of computer simulation and engine testing the optimum extent of the
    groove may be determined. It is not now just a case of allowing the big end to survive but
    that the efficiency of the bearing system can actually be improved by due attention to the
    groove geometry. This is because the big end bearing, like any hydrodynamic lubricated
    bearing, will use as much oil as it needs to generate an oil film for any given operating
    condition. Any less than this amount risks disrupting the oil film and ultimately starving the
    bearing of oil, but equally, feeding excessive oil to the bearing simply results in additional
    leakage, and reduced efficiency. Therefore, the oil groove, like many other features on a
    bearing shell, can be optimised.

    read thru these links ... forman.pdf ... ooving.pdf

    TB 2051 2/10/2000
    Influence of Grooving on Main Bearing Performance
    Various forms of main bearing grooving have been used over the years. We are
    frequently asked what difference grooving makes.
    First, it’s essential to understand that bearings depend on a film of oil to keep them
    separated from the shaft surface. This oil film is developed by shaft rotation. As the shaft
    rotates it pulls oil into the loaded area of the bearing and rides up on this film much like a
    tire hydroplaning on wet pavement. Grooving in a bearing acts like tread in a tire to break
    up the oil film. While you want your tires to grip the road, you don’t want your bearings
    to grip the shaft.
    The primary reason for having any grooving in a main bearing is to provide oil to the
    connecting rods. Without rod bearings to feed, a simple oil hole would be sufficient to
    lubricate a main bearing. Many early engines used full grooved bearings and some even
    used multiple grooves. As engine and bearing technology developed, bearing grooving
    was removed from modern lower main bearings. The result is in a thicker film of oil for
    the shaft to ride on. This provides a greater safety margin and improved bearing life.
    Upper main shells, which see lower loads than the lowers, have retained a groove to
    supply the connecting rods with oil.
    In an effort to develop the best possible main bearing designs for High Performance
    engines, we’ve investigated the effects of main bearing grooving on bearing performance.
    The graphs on the next page illustrate that a simple 180
    groove in the upper main shell is
    still the best overall design.
    While a slightly shorter groove of 140
    provides a marginal gain, most of the benefit is to
    the upper shell, which doesn’t need improvement. On the other hand, extending the
    groove into the lower half, even as little as 20
    at each parting line (220
    in total), takes
    away from upper bearing performance without providing any benefit to the lower half.
    It’s also interesting to note that as groove length increases so do Horsepower Loss and
    Peak Oil Film Pressure which is transmitted directly to the bearing
    Last edited by a moderator: Mar 24, 2017
  2. grumpyvette

    grumpyvette Administrator Staff Member ... NG-SPACERS
    Part Number Description Price Qty Add
    EB-MB5224AM Chevy 350 to 400 Spacer $49.99 ... K,533.html

    400 sbc block/350 crank main bearing spacers

    theres also TRW MS3110P is the part number for a main bearing set to put a standard pre 1968 small journal (283, 265, sj327) crank into a medium journal (350) block ... index.html

    IT should be obvious that you'll need to pre-prime the blocks oil passages and adjust the rockers so oil flows from the rockers with the engine being pre-primed with a priming tool being used BEFORE trying to start any engine with a new cam to insure oil flow begins instantly on the engines start-up,you WON,T get oil to all lifters equally unless the engines crank & cam are spinning,(so during testing spin the engine slowly with a breaker bar or ratchet), because the oil passages feeding the lifters aligns differently at different lifts,your oil leak at the distributor base is normal, but the clearances and flow may be excessive, with a priming tool, some are not nearly to spec. ID measure the diam. of the oil pump primer and then measure the distributor base, Id bet the distributor base is larger and fits better, which reduces the potential for leakage.
    those bottom two bands form a wall on the oil passage, some guys cut a rounded grove and install an O-RING so the upper band seals too the block, you don,t want to do that to the lower band simply because that's the oil flow source to the distributor /cam gear
    20 psi is about normal for your typical 3/8 drill,max pressure is not nearly as important as checking flow, and for leaks where there should not be leaks, with an engine primer tool,Ive brazed a socket to the top of my oil pump primer and use the 1/2" drive air ratchet to drive it, it won,t heat up and burn up like a electric drill will.
    don,t get alarmed if you get zero pressure or flow for a few seconds,(the oil filter and passages need to fill first) that's one reason WHY your pre-priming, to get oil flow to the bearings instantly on start up , you don,t want them running without oil flow if you can prevent it even for 20 seconds
  3. grumpyvette

    grumpyvette Administrator Staff Member

    IF your having excessive oil heat problems with an engine, my
    first suggestion swap to a decent synthetic oil in the 10w30 range or at least the thinnest viscosity that maintains 20 psi at hot idle temps, as SYNTHETICS don,t generally start breaking down until about 280F PLUS while mineral base oils tend to start degrading after repeated 250F use, and the thinner the oil the faster it circulates thru the clearances, and the faster heats absorbed and transferred out off the hotter components
    and Id need to know more about the complete engine parts list, clearances, etc. but Id sure want to verify the fuel/air ratio is at about 12.6:1 not alot leaner and your ignition timing was carefully checked to not be a couple degrees advanced from ideal., and that your running a 7-8 quart oil pan, heres the oil cooler I use and I had to install a thermal switch or it OVER COOLED my engine oil in FLORIDA where average outside air temps closer to 90F
    oil does most of an engines real cooling and the cooling system allows heat absorbed by the oil and transferred to the block to be transferred to the coolant and removed, but a significant percentage of that heat can be removed if an efficient oil cooler is installed, that maintains a significantly lower average oil temp while the engines under stress., think about it a second. the HOT PARTS like rings, valves, cams, lifters, bearing surfaces and valve springs and pistons get cooled mostly by oil splash or pressurized oil flow not direct coolant contact

    my oil pan looks similar to this ... 88bb985ecf
    Canton Oil Pans
    11-120 and 11-120T Oil Pans

    but I extended the sump forward with 14 ga steel and a tig welder to add 4 inches extra to the sump to get 10 qt capacity ... mage=large


    But I was always under the impression that Chevys liked thicker mineral oils, and I should avoid synthetics? Not true then?

    IVE run a MIX of 90%/ synthetic 10% mineral oil in my race cars for many years

    usually 1 qt MARVEL MYSTERY OIL, 9 qts MOBILE 1 10w30 synthetic ... /Oils.aspx

    obviously these won,t fit all chevy applications but if you have the room for the longer, spin on filters

    The "longer high capacity oil filter" Purolator is L40084.

    "longer high capacity oil filter" N.A.P.A: # 1794

    "longer high capacity oil filter" ACDelco: PF932

    keeping the oil cool basically comes down to having the oil flow thru both the engine and the cooler but having the surface area of the cooler large enough and the number of passes thru the cooler ,allow the oil to transfer most of the heats its absorbed in the engine back out into the air flowing thru the cooler,before its routed back to the engine,and that generally requires ducting cool air into the cooler and placing it where the flows not restricted, on my corvette I removed the rear spare tire, and built a mount that allowed a good deal of clearance and no significant engine heat, with it working all the time I had problems getting the heat over 220 f and it mostly stayed at or near 200f,theres basically about 3 qts in the upper engine and oil passages at any time , absorbing heat so having a similar volume in the cooler, releasing heat during the same time makes sense, and having a similar amount in the baffled oil pan sump and filter sure helps,naturally if you have the oil routed to spend more time with the majority of the oil being heated and less of the oils times spent cooling average temperatures rise rapidly
  4. grumpyvette

    grumpyvette Administrator Staff Member

    theres some confusion as to the correct oil pan size and dip stick markings,, ILL try to keep this simple, basically the oil pan should never be less than a 5 qt capacity in a performance application, and as long as clearances under the car permit a 6-7-8 or larger capacity baffled oil pan with a windage screen is preferred, some guys will suggest restricting oil flow return routes to the sump by installing lifter valley breather tubes, but a decent cranl scraper and windage screen on a high capacity baffled oil pan reduces windage losses significantly, and that oil cools the pistons, rings and cam and lifters so reducing its ability to cool and lube those components by restricting flow is not a great idea

    theres about 2-3 quarts of oil in a running engine thats not sitting in the sump, around the oil pump that lowers the oil pan oil level a good deal, normal 5 qt oil pans still have 2-3 qts around the pickup, but that lowers the oil level in the oil pan in most cases about 2-3 inches while the engine runs, so most dip sticks measure the correct oil level as about 2" up on the crank counter weights, because once the engines spinning that puts the oil level below the windage screen or at least below the spinning crank.
    DIP STICKS are NOT always correctly marked,you should be able to research your oil pans intended capacity, Id suggest running NO LESS than a 5qt capacity oil pan and a baffled 6-7-8 qt is vastly preferable if your not sure add 5 qts to an empty oil pan and start the engine for a minute to fill the oil filter and oil passages, then look at where the oil level is in relation to the indicator band on the dip stick so you know what the minimum level should be, if its significantly lower than the dipstick marks, add the required oil level the pans rated for and pay attention to the dipstick.
    just remember oil levels drop several inches once the engines running and as the rpms increase the level tends to drop slightly more, your very unlikely to (PUMP THE PAN DRY) like you commonly hear as a MYTH with the high volume oil pumps, because hot oil with a well designed oil pan and windage tray drains back into the sump quickly and the vast majority of the oil never makes it to the upper engine as its leaking from rod, man and cam bearings and lifter bores and gets swept back into the sump.
    now it should be obvious that to use a high volume oil pump you need a MATCHING high capacity baffled oil pan and windage screen to CONTROL the extra oil flow rates, and the bearing, and other engine clearances and oil drain holes in the block should be designed to use the extra oil flow.



  5. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    if your serious about building engines as a hobby or even as a part time side business,
    you'll be forced to either buy or borrow some decent quality precision measuring micrometers,
    simply due to the need to check clearances accurately (ABOUT $250 a set)
    (ABOUT $415 a set)
    (ABOUT $877 a set)
    dial bore gauges are about useless without a set of accurate mics, in the sizes of the bore diameter your checking as you use a dial bore gauge to measure consistency in a given bore size and basically how consistent or "ROUND" a bearing is but you use the mics to verify dimensions.
    in my opinion you,ll also be smart to cross check ,bearing clearances with plasti-guage

    [​IMG] [​IMG] [​IMG] [​IMG]

    Last edited: Jan 6, 2017
    Strictly Attitude likes this.
  6. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    IF you find metallic glitter in your oil during any oil change that metal came, from someplace,and things are likely to get worse over time, if the engines still driven, ,if you pull it down for a close detailed inspection NOW, you might find its fairly cheap and easy to repair,
    COMPARED, too what it will be inevitably if you continue to drive it in its current condition,
    as all that metallic trash in the oil WILL constantly continue to do ever more DAMAGE

    read through these links, the time spent will be well worth the effort anf knowledge gained should help

    moroso sells plug kits
    be sure only one oil passage plugs drilled, generally only the pass side oil passage plug with a single .025-.030 hole, many guys use a 1/32" drill bit because its easy to locate, I prefer the smaller #72 drill

    Last edited: Apr 6, 2017
    Strictly Attitude likes this.

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