how your oil pumps pressure bye-pass circuit works,

[grumpyvette]

theres seems to be a lot of mis-information about , how the oil pump regulates its pressure curve, and the related subject of shimming oil pump springs and how your oil pumps pressure bye-pass circuit works.
PRESSURE, that you see displayed on the oil pressure gauge is a measure of the RESISTANCE to oil FLOW thru the engines clearances and its dependent on moth flow volume and oil viscosity, plus the cross sectional area of those clearance,s, but remember the oil viscosity changes with temperature.
keep in mind the oil pump spins at 1/2 the speed of the crank so at 2000rpm on the tach the oil pumps spinning at 1000rpm. and the oil pump gears teeth move a set volume of oil flow thru the pump at any rpm level, the oil trapped by the pumps gears can only move as much oil volume as the gears sweep volume allows, high volume oil pumps have longer gears,of similar diameter to stock gears,the extended length is there to add more volume, so they trap and push a greater volume of oil thru the pump body, with each rotation.
standard volume oil pumps use shorter gears than high volume oil pumps, the 10%-25% extra flow is the result of the 10%-25% extra gear length
Ive 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 .oil pressure, will be determined by the difference in RESISTANCE too oil flow volume produced by the pump and the volume exiting the bearing clearances listed below, up to the point where the by-pass piston,held closed by the by-pass spring resistance , of that spring is forced open allowing oil to recirculate thru the pump to the low pressure side, limiting further pressure increases. as the oil temp increases the viscosity tends to decrease, this, lower viscosity or thinner easier to pump hot oil, flows thru the clearances faster,this lowers the resistance to flow thru clearances thus the pressure drops as the resistance to flow decreases
OIL PRESSURE read on the 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, 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 it has zero to do with anything else, if its functioning correctly,During testing the bye-pass circuit in the oil pump should open, allowing high pressure oil to flow back to the feed or low pressure side of the oil pump, and limit oil increases,in pressure too either about 60-65psi or 65-70psi depending on the resistance of the bye-pass spring selected
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.)
your 55 psi at idle serves no purpose as 15psi-25psi is all thats expected in a new engine with tight clearances using a good 10W30 oil, if your using a higher viscosity than 10w30 its reducing oil flow rates and reducing heat transfer rates, Id suggest using a good 10W30 oil. and use of a 7-8 quart, baffled oil pan and windage tray
the idea that you can 'pump the pan dry" with a high volume oil pump, in a properly set up chevy engine has been proven false dozens of times, thats a myth , oil pumped thru the engine drains back to the sump rapidly in a properly set up engine.that myth been repeated for decades and the reason its gained its supposed verification as fact is simply that guys install a high volume oil pump in the same engine that they just removed a stock oil pump from and find that they reve the engine and the oil pressure starts to go up then tops out or even drops off , the instant and wrong conclusion drawn is that the high volume oil pump sucked the oil pan dry, but what really happened in almost every case was a bit simpler.
high volume oil pumps have a longer body that moves the oil pump pick-up closer to the oil pan floor and if the clearance is not checked and corrected to maintain the required 3/8"-1/2" minimum clearance it severely restricts the flow into the oil pump and pressure drops of as a result of the restriction on the intake side of the oil pump pick-up.










your typical small block oil pump has a 4 bolt cover, a 5/8" pick-up tube diameter and the pick-up presses into the cover , it has the smaller 7 tooth gears, and because the pick-up tube presses into the cover swapping from a standard to a high volume pump, with its longer impeller and hoseing casting, tends to move the pick-up about 1/4" closer to the oil pan floor
keep in mind that as oil temps increase the oil viscosity tends to decrease, thus cold oil, at lets say 70F might cause the oil pressure gauge to read 50 psi at idle but the pressure reading slowly goes down to 25 psi once the oils reached lets say 210F, this is normal and expected


REMEMBER the oil pump bye-pass is designed to limit oil pressure reaching the oil passages in the block,to usually 65psi-75psi max, by opening and re-routing oil from the pressure side of the oil pump to the suction side of the gears one its forced open, this is not the same and has nothing to do with the oil filters oil bye-pass valve,
yes the BYE-PASS IN THE OIL FILTER DOES normally open on cold mornings, or under rapid changes in engine rpms, especially before the heat from the engine lowers the oils effective viscosity, Im fairly sure you have heard or remember hearing advise not to go doing stupid stuff like burn outs in your drive way until the engines reached and maintains operational temps
(usually oil and coolant has reached 190F-215F) well one big reason is that thicker oil viscosity when oils cooler ,takes a good deal more pressure to force thru the filter medium, once the oils fairly hot it flows better, and requires less pressure as it offers less resistance to flow thru the engines clearances and thru the filter, that in turn means that hot oil with its thinner effective viscosity tends to be far less likely to force open the filter bye-pass circuit and that means oil bye-passing the filter medium is far less likely to drag metallic trash held in suspension with it to reach the bearings to cause more rapid wear.the oil filter bye-pass is designed to bye-pass oil to the engine rather than forcing it thru the oil filter any time the pressure on the inlet side of the oil filter is higher than about 10 psi over oil pressure passing thru the oil filter, this in theory prevents the semi clogged oil filter from starving the bearing of oil.but it also means that during rapid rpm changes or before the oils up to operational temps some oil is routed around and past the filter, under the concept that dirty pressurized oil is far superior to no oil reaching the bearings.
MORE USEFUL INFO



failure to use the correct oil pump,mounting stud, bolt or nut or carefully check clearances when mounting an oil pump can cause problems


ONE RATHER COMMON MISTAKE IS USING THE WRONG OIL PUMP STUD OR BOLT TO MOUNT THE OIL PUMP AS IF EITHER EXTENDS THRU THE REAR MAIN CAP IT CAN AND WILL BIND ON THE BEARING AND LOCK OR RESTRICT, SMOOTH ROTATION

I like high voluum pumps but I certainly don,t use them IF the engines nearly stock as the standard Z28 SBC pump works fine
"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












the true high voluum pumps like this below are not necessary UNTILL youve done extensive mods that require the expra oil flow voluum

14044872
SBC Oil Pump, High-Volume. This high-volume pump has1.50" long gears.It has approximately 25% more capacity than a production pump at standard pressure. Does not include screen."
http://www.melling.com/Aftermarket/Tech-Tip-Videos
viewtopic.php?f=54&t=2187
ONE VERY COMMON MISTAKE MADE by guys swapping to a high volume oil pump is failure to carefully measure the pick-up to oil pan floor clearances, because the high volume oil pump has longer gears it tends to move the location of the oil pump pick-up lower towards the oil pan floor, if that distance is reduced too less than about 3/8" the common symptom is good oil pressure at idle but rapidly falling pressure as the rpms build as the oil pump intake is restricted significantly, this results in the common MYTH that high volume oil pumps pump the pan dry as rpms increase. when the truth is that its the result of not carefully verifying clearances
the answer to that question of what SMALL BLOCK CHEVY PUMP TO USE, depends on the application and the size of your oil pan, if your using a windage tray, your bearing clearances and a dozen other factors, reading thru the links posted below should be very helpful.
youll seldom have any problem using melling 10552, if its properly installed, in almost any small block, is roughly similar to the old Z28 pump and supplies a bit of extra volume at near stock pressure if you don,t install the optional high pressure spring, that pump should be fine in about 90% of the street strip engine builds


http://www.summitracing.com/parts/mel-10552
[b]
related threads to read thru

viewtopic.php?f=54&t=2187

viewtopic.php?f=54&t=1800

OIL PUMP MODS
http://www.corvette-restoration.com/res ... ancing.htm

http://www.youtube.com/watch?v=tOiHdIXV ... r_embedded

viewtopic.php?f=54&t=64

viewtopic.php?f=54&t=52

viewtopic.php?f=54&t=5202

viewtopic.php?f=54&t=123&p=326#p326

viewtopic.php?f=54&t=2294

READ THIS THREAD[/b]









small block pumps have 7 tooth gears and 4 bolt covers and don,t provide the smooth oil flow rates the 12 tooth, and 5 bolt cover big block gear pumps provide


In this comparison, you can see the major difference between a high-volume small-block pump gear (left) and the Rat motor gear (right). The Rat motor pump enjoys a larger diameter and more pump teeth that should create a more stable output curve.

Read more: http://www.carcraft.com/techarticles/cc ... z2RyXV6xCI

big block vs small block chevy oil pump

your typical small block oil pump has a 4 bolt cover, a 5/8" pick-up tube diameter and the pick-up presses into the cover , it has the smaller 7 tooth gears

your typical big block oil pump has a 5 bolt cover, a 3/4" pick-up tube diameter and the pick-up presses into the pump body , it has the larger more efficient 12 tooth gears and in many cases can be mounted on a small block, but its usually not required
BIG BLOCK CHEVY 5 BOLT cover pump


SBC 4 BOLT COVER OIL PUMP

SBC pumps have 7 tooth gears and BBC pumps generally have 12 tooth gears making the flow more consistent

oil is sucked up the pick-up (or pushed in by the pressure difference, if you need to be technical) into the pump body and swept along the outside walls of the pump,by the rotating gear teeth,and forced thru the pumps pressurized exit port passage in the pump casting, then the pressurized oil is forced thru the rear main cap on the block, fluids are not compressible, so , if the resistance to the oil flow increases, the resulting oil pressure increases until it exceeds the bypass circuit springs resistance, on the bypass circuit piston , this forces open the bypass circuit piston in its bore allowing the excess pressurized oil to bleed back into the low pressure side of the oil pump casting, thru a passage in the oil pump casting designed to limit peak oil pressure,that the spring loaded piston in the pressure relief circuit controls, the flow rate, until the pressure drops below the oil pumps pressure relief spring resistance , when the spring forces the passage to close as the small piston on the spring closes the pressure relief passage acting as a valve, that controls and limits peak pressure.
the pumps secured to the rear main cap with a stud or bolt and its indexed with the twin pins,in the rear main cap, that fit the holes in the pump casting.
the pumps spun with a drive shaft that connects the distributor gear and cam gear interface
the by-pass circuit has no effect on oil pressure other than to control the peak pressure, that can be reached before the circuit opens and limits further increases, installing a stiffer spring only delays the circuit opening point until a higher pressure is reached and has zero effect on the oil pressure up to that point in the pressure curve. a common problem is guys failing to remove the spring & piston assembly prior to brazing the oil pump pick-up onto the pump casting as the heat can anneal the spring temper reducing its resistance, thus reducing the pumps peak pressure or failing to clean and oil and properly re-assemble the oil pumps by-pass circuit components which can result in the piston binding in its bore and not allowing the by-pass circuit to open and function at all.
in years past it was fairly common to use a small washer to shim the by-pass spring to add a few extra pounds of resistance before the circuit opened, if done correctly this worked but it was common for guys to screw it up and its not advisable to go that route, as stiffer springs designed for the job are cheap and easy to install.
I,d also point out that while oil pressures over 60 psi are certainly easily reached they provide little or no improvement in lubrication, you need to try to maintain a minimum of about 10-15 psi per 1000rpm and Ive generally found a 20-25 psi at hot idle and 60-65 psi at peak rpms to be ideal.



the oil pump pumps oil out this exit passage to the main cap


heres the matching rear main cap surface


below you can see the inlet and outlet for the pressure relief passage in the big block oil pump(remember big block pumps have the pick-up in the main pump body while sbc pick-ups are mounted into the pump cover plate)



look at the picture below, the restrictive stock O.E.M. pickup if placed to close to the oil pan floor becomes a HUGE restriction to oil flow rates

you should NEVER shim an oil pumps pressure relief spring as it may prevent the piston it holds from moving down its bore far enough to allow it to open the bay-pass passage, that allows the pressure on the high pressure side of the oil pump from bleeding off back into the intakes side of the oil pump

Many pressure relief springs have one end larger than the other end,the spring always mounts with the larger end facing away from the bypass piston, if installed reversed the piston can,t move far enough to completely open the bypass circuit passage and pressures skyrocket, under some conditions


there are oil pump testers available commercially or if your mechanically inclined you can fabricate one with reasonable care, after a bit of measuring and purchasing a gauge
http://cvrproducts.com/oil-pressure-test-kit/

one point I should mention is that if you manage to wipe out a lifter and cam lobe, much of the the metallic trash is ALWAYS sucked thru the oil pump gears and its frequently packed into the pressure relief ports significantly reducing oil pump efficiency, so at a minimum it will require dis-assembly and careful inspection and cleaning and, if run awhile before you detect the problem, usually replacement













theres a great deal more info in these threads & links

http://www.chevyhiperformance.com/techa ... index.html

viewtopic.php?f=54&t=2376

http://www.livermoreperformance.com/gm_oil_acc.html

viewtopic.php?f=54&t=1192&p=2467#p2467

viewtopic.php?f=54&t=52

viewtopic.php?f=54&t=2294&p=13460#p13460

viewtopic.php?f=54&t=2187

viewtopic.php?f=54&t=1800&p=5526&hilit=brazed#p5526

viewtopic.php?f=50&t=382&p=467&hilit=MAIN+CAPS%E2%80%A6#p467

[grumpyvette]

ITS a good idea to inspect the oil filter internals when you change oil as it may allow you to detect a problem with cam or lifter or bearing wear far earlier than you might otherwise detect it.

http://store.summitracing.com/partdetai ... toview=sku


viewtopic.php?f=54&t=117

its basically a heavy duty can opener designed to make it easy to internally inspect oil filters, by allowing you to remove the filter element , from inside the surrounding (CAN) for close visual inspection.
If you don,t have one, and have not used one, your unlikely to see, or appreciate the benefits,close inspection can and does frequently give you prior evidence of impending or at least gradually occurring wear and with practice you can make an excellent guess as to the parts and condition of those components.
IT also helps to trap crud if you install a couple high temp magnets on the filter and in the oil pan.

btw, add a few magnets to the oil pan and drain back area in your engine, the trap and hold metallic dust that comes from wear and increase engine life span by preventing that crap embedding in the bearings

http://www.kjmagnetics.com/proddetai...d=D66SH&cat=13

http://www.kjmagnetics.com/proddetail.asp?prod=D66SH

http://www.kjmagnetics.com/proddetail.asp?prod=D82SH

these are even more tolerant of temp swings and retain strength at even higher engine oil temps plus they are smaller and easier to use

The SH material in the D66SH magnets, means that the magnets can be heated to 300° F without any loss of magnetic strength, unlike standard neodymium magnets that begin to lose strength at 175° F. Suitable for many high temperature applications.

BTW if you break in a new engine or install a new high voluum oil pump and find oil pressure , peaks at less than 60 psi,remember pressure is a measure of the resistance to flow,if your oil pressure peaks at less than 60 psi, the first thing Id suggest is checking with a separate oil pressure gauge and sensor because its hardly rare for those sensors to be defective.
FLOW IS THE KEY HERE!
now if the oil pump pick up is mounted too close to the oil pan floor it restricts oil flow rates entering the pump and as the rpms increase so does the flow up to the point the oil flow can,t enter the pick-up due to the restricted area between the oil pump pick up and the oil pan floor.
this will produce the exact symptom your describing, and can happen at 20psi, 30psi, 40psi,, depending on the bye-pass spring which may be weak and opening early or clearance between the pick-up and oil pan floor,but its not the only possible cause., and its the source of the myth that high volume oil pumps pump the oil pan dry, because high volume oil pumps sit lower in the pan and if you don,t carefully check oil pump pick-up too oil pan floor clearance theres a good chance swapping to the longer pump restricted oil flow into the pump.
the next thing to do is swap to a thicker viscosity oil (save the old oiil) and a new oil filter, if the pressure increases, on both gauges to well over 40 psi, to 60 psi you know the gauge is reading the resistance and its not the oil pumps bye-pass because if thats defective, or the pumps intake pick-up clearance, is restricted, the bye-pass circuit will still open at 40 psi. and the pumps still restricted, if pressure goes up, with the thicker viscosity, and new oil filter theres a good chance its the bearing clearances, or the old oil filter was restricted, if you, now drain the oil and put the old oil back, but keep the new oil filter, and it still has the higher oil pressure it was obviously a restrictive filter. if it returns to the 40 max psi, theres a good chance its a restricted pump inlet or defective bye-pass circuit,or excessive clearances
the aftermarket drive shafts are held to a much higher strength tolerance, and a steel collar and and the reduced mid section are both good features, for the very low price Id strongly suggest pitching the stock drive shaft in the dumpster
be sure you select the correct oil pump drive shaft
SB - is a bit shorter about 5.75"
BB - is a bit longer about - 6.50" or so
there should be about .050 vertical movement, of the oil pump oi,l pump drive shaft between the oil pump and lower distributor gear with the manifold and distributor seated correctly

heres two related thread to read

viewtopic.php?f=54&t=3536

viewtopic.php?f=54&t=150

[grumpyvette]

BTW HERES AN IMPORTANT TIP, IF YOUR INSTALLING A REMOTE OIL COOLER, IT is really common for guys to use lines that are far too small, that restrict flow oil flow or select a transmission or oil cooler that has to small of internal passages, shop carefully you want a MINIMUM of 1/2, or AN8 line size and 5/8" or AN10 is BETTER.
[b]many guys don,t realize that adding an oil and/or a transmission fluid cooler, with its own fan and radiator that allows those liquids to be cooled separately, to your engine and drive train, significantly reduces the heat load on the radiator, and generally allows the engine temps to decline noticeably. in fact just adding a high volume oil pan and a transmission cooler can drop your engine coolant temps 20F-30F in many cases
OIL PRESSURE read on the 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, 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 it 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.)
your 55 psi at idle serves no purpose as 15psi-25psi is all thats expected in a new engine with tight clearances using a good 10W30 oil, if your using a higher viscosity than 10w30 its reducing oil flow rates and reducing heat transfer rates, Id suggest using a good 10W30 oil. and use of a 7-8 quart, baffled oil pan and windage tray


(NOTICE ITS A 4 BOLT small BLOCK HIGH VOLUME OIL PUMP WITH A 5/8" pickup}
10553

10553High pressure performance upgrade for M-55 & M-55A.
Standard volume oil pump.
The 10553 housing and cover are CNC machined and phosphate coated.
Manufactured with pink spring installed for higher pressure (M-55A).
To change pump to lower pressure (M-55) install the supplied yellow spring.
Includes intermediate shaft with steel guide.
The 10553 uses a 5/8” press in screen.

10552

High volume performance oil pump.
10% increase in volume over stock oil pump.
The 10552 is manufactured with the drive and idler shafts extended to allow for additional support in the cover eliminating dynamic shaft deflection at increased RPM levels.
The cover is doweled to the pump housing to assure alignment of the shaft bores.
Screw in plug retains relief valve spring instead of pin.
Relief hole in cover uses screw in plug instead of pressed cup plug.
All bolts are self locking socket heads, with the wrench supplied.
The housing and cover are CNC machined and phosphate coated.
Includes intermediate shaft with steel guide. Uses both 3/4” bolt on or press in screen.
The lower pressure spring is included to reduce pressure if desired.
Patent No. 5,810,571.

10778C (Anti-Cavitation)
(NOTICE ITS A 5 BOLT BIG BLOCK HIGH VOLUME OIL PUMP WITH A 3/4" pickup}
http://www.summitracing.com/parts/mel-10778
High volume performance upgrade for the 10770.
Increase in volume of 25% over stock oil pump.
The same as the 10778 except with the addition of grooves machined in the housing and cover. The grooves reduce cavitation effects in high RPM applications.
Using this oil pump will reduce pressure at idle.
Includes intermediate shaft with steel guide.
Uses 3/4” press in screen.
Racing applications only.
Patent No. 5,810,571


from chevy high performance mag










you might want to read thru these links and sub links,
as theres a great deal of related useful info contained


viewtopic.php?f=54&t=2187

viewtopic.php?f=54&t=52

viewtopic.php?f=54&t=2102

viewtopic.php?f=54&t=64

viewtopic.php?f=54&t=1334

obviously the first two steps in diagnosing any oil pressure problem you suspect is to check your dipstick for the proper oil level in the engine and then test the pressure with an independent test gauge to verify your cars gauge is correct, and you do have a problem , not a defective sensor or gauge
the oil pressure sensor location, is next to the distributor base,on most sbc engines on the rear of the block, but if your trying to track down an oil pressure issue it could be either a bad sensor, bad connection on the sensor or gauge, or a defective gauge, causing the high pressure reading OR it may be a defective oil pump, or bearing clearances or an oil passage plug, or the wrong oil viscosity, or a busted oil pump pick-up or incorrect installation of the oil pump or pick-up,defective oil filter or several other potential sources if its a low pressure issue as previously mentioned.


broken , or improperly installed oil pump pick-ups can cause several major oil pressure issues





http://forum.grumpysperformance.com/viewtopic.php?f=54&t=3536




http://www.harborfreight.com/engine-oil ... 92687.html

you MUST have an independent oil pressure gauge to verify any oil pressure issue before you start randomly replacing components or pulling the oil pan


oil pressure switch to fuel pump

gauge sensor, both connect near distributor base at rear of the block



temp sensor, mounts near oil filter
theres several block port locations to check oil pressure or instal sensors, theres several, but different castings vary locations





C4 Sensor Information

http://www.aa1car.com/library/air_temp_sensors.htm

The C4 Corvette makes use of numerous sensors that feed information to the ECM/PCM (Electronic Control Module/Powertrain Control Module) and to the instruments on the dashboard.

Even if the sensor is operated by vacuum or pressure, the output is converted into an electrical signal for processing by the ECM.

Most faulty sensors will cause a trouble code to be set (resulting in a 'Check Engine/SYS ' Light) and also alter the performance of the automobile.

When troubleshooting the reason for the code, the normal approach is to go straight to the sensor and assume that it is faulty.

While this may be the normal practice, you are strongly cautioned that it is seldom the sensor but rather a connector, a power problem or a grounding issue that is actually causing the problem.

Or, the sensor may simply be doing it's job and reporting an occurrence that is at variance with what is allowed or expected by the ECM/PCM.

In any event, because the sensor really is the easiest thing to check, the following information is provided to assist you in determining if the device is operating properly.

You will need a D-VOM (Digital Volt-Ohm Meter) to check the items below. It should have at least a 10 megohms per volt rating---something that will be shown in the specifications.

For those sensors listed below that have ohms listed as the measurement item, disconnect the negative battery terminal and then the sensor harness connector and measure the sensor's terminals.

For voltage measurements, you can obtain test harnesses from any of the Corvette specialty catalog houses.

Before beginning your efforts, print the ECM codes page along with this page so you can cross reference the code information with the sensor information.

Sensor Outputs:

Sensor


Measured Value

Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. (lower sensor above oil filter) 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.

some early c4 vettes have the gauge and oil pressure switch on an adapter near the distributor base into the block


Oil Pressure Sender/Switch. (top sensor in picture above) 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.

Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.

low coolant sensor
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.


MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.

Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.

TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

KNOCK SENSOR
Sensor Locations

Sensor


Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.

[grumpyvette]

BTW this tool can save you hours of what could be un-necessary work ,you might otherwise do, pulling an oil pan under some conditions to do internal inspections, simply drain the oil and insert the tool to inspect the oil pump pick-up and its clearance to the oil pan floor which is frequently the info you need to diagnose a problem.
I know Ive used my tool dozens of times to prove to guys its a defective pick-up on the oil pump or a bad installation or not enough clearance to the oil pan floor causing their pressure issues
ITS also great for finding bent valves or cracks in combustion chambers, worn cam lobes, detonation damage on pistons, cracked cylinder walls, under some conditions,
BTW it helps to have a length of 20lb fishing line tied on the tip as it helps you bend and move the view once its inserted in the oil pan

http://www.toolrage.com/prodView.asp?sku=SLI-PV618


http://www.thetoolwarehouse.net/shop/SLI-PV618.html

ProVision 618 Flexible Fiberscope w/ 18" Non-Obedient Shaft



High resolution lens provides a clear image of objects as close as 3/4 inch and over one foot away while providing a wide 40 degree field of view.
Powerful lamp illuminates dark crevices on-demand with the push of a button conveniently located on the handle.
Ergonomically designed handle is comfortable to hold and allows one-handed focusing and light activation.
Rugged and water resistant, ProVision is made of high impact ABS and flexible cable sheathing. (Note: Shaft is water resistant, not the handle.)
PV-618 and PV-636 models have .23” diameter, flexible, non-obedient cable. Durable carrying case included.
Accessories available to optimize ProVision for specialized applications.
Made in the USA
Specifications:

Cable Length: 18" (457.2mm)
Cable Diameter: .23"
Handle Length: 6" (152.4mm)
Handle Width: 1.43" (36.2mm)Overall Length: 24" (609.6mm)
Weight of Scope w/ Carrying Case: 1 lb. 5.7 oz (615 g)
Field of View: 40°
Optimal Viewing Distance: Min. .8" (20mm); Max. is dependent upon ambient lighting conditions.
Lamp Volts: 2.7 volts (Halogen)
Power Source: 2 AA batteries (not included)
Pressure Necessary to Operate Lamp: 2.9 avg. p/psi; 3.2 max. p/psi


drain your oil , and you can use the flexible scope and look at the oil pump clearance to the oil pan floor, the oil pump pick-up and its brazed joint,the cam, pistons and bore walls etc, thru the oil pan drain hole, or pull a spark plug and inspect the valve or piston condition



http://www.toolrage.com/prodView.asp?sku=SLI-PV618

http://www.toolrage.com/prodview.asp?sku=SLI-PV300

OIL PUMP MODS
http://www.corvette-restoration.com/res ... ancing.htm

[grumpyvette]

http://www.summitracing.com/search?keyword=5556F&dds=1
(chevy small block oil pump bye-pass springs)

http://www.summitracing.com/parts/mel-77060
(chevy big block oil pump bye-pass springs)

GM Small Block Performance Pumps
10550

High volume performance upgrade for M-55HV.
25% increase in volume over stock oil pump.
The 10550 housing and cover are CNC machined and phosphate coated.
The lower pressure spring is included to reduce pressure if desired.
Includes intermediate shaft with steel guide. Uses 5/8” press in screen.





10551

High volume performance upgrade for M155HV.
25% increase in volume over stock oil pump.
The 10551 housing and cover are CNC machined and phosphate coated.
The lower pressure spring is included to reduce pressure if desired.
Includes intermediate shaft with steel guide. Uses 3/4” press in screen.





10552

High volume performance oil pump.
10% increase in volume over stock oil pump.
The 10552 is manufactured with the drive and idler shafts extended to allow for additional support in the cover eliminating dynamic shaft deflection at increased RPM levels.
The cover is doweled to the pump housing to assure alignment of the shaft bores.
Screw in plug retains relief valve spring instead of pin.
Relief hole in cover uses screw in plug instead of pressed cup plug.
All bolts are self locking socket heads, with the wrench supplied.
The housing and cover are CNC machined and phosphate coated.
Includes intermediate shaft with steel guide. Uses both 3/4” bolt on or press in screen.
The lower pressure spring is included to reduce pressure if desired.
Patent No. 5,810,571.

10552C (Anti-Cavitation)

10552CHigh volume performance oil pump.
10% increase in volume over stock oil pump.
Same as the 10552 with the addition of grooves machined in the body and cover. The grooves reduce cavitation effects in high RPM applications.
Includes intermediate shaft with steel guide.
Uses both 3/4” bolt on or press in screen.
Using this oil pump will reduce pressure at idle.
The 10552C uses the high pressure spring only.
Racing Applications Only.
Patent No. 5,810,571.

10553

10553High pressure performance upgrade for M-55 & M-55A.
Standard volume oil pump.
The 10553 housing and cover are CNC machined and phosphate coated.
Manufactured with pink spring installed for higher pressure (M-55A).
To change pump to lower pressure (M-55) install the supplied yellow spring.
Includes intermediate shaft with steel guide.
The 10553 uses a 5/8” press in screen.



10554

Performance upgrade for M155. Standard volume oil pump.
The 10554 housing and cover are CNC machined and manganese phosphate coated.
Manufactured with pink spring installed for higher pressure.
To change pump to lower pressure install the supplied yellow spring.
Includes intermediate shaft with steel guide.
The 10554 uses a 3/4” press in screen.



10555

High Volume performance upgrade for the 10550 oil pump.
25% increase in volume over stock oil pump.
The 10555 is manufactured with the drive and idler shafts extended to allow for additional support in the cover eliminating dynamic shaft deflection at increased RPM levels.
The cover is doweled to the pump housing to assure alignment of the shaft bores.
Screw in plug retains relief valve spring instead of pin.
Relief hole in cover uses screw in plug instead of pressed cup plug.
All bolts are self locking socket heads, with the wrench supplied.
The housing and cover are CNC machined and manganese phosphate coated.
Includes intermediate shaft with steel guide.
Uses both 3/4” bolt on or press in screen.
The lower pressure spring is included to reduce pressure if desired.
Patent No. 5,810,571


10555C (Anti-Cavitation)

High volume performance upgrade for the 10550 oil pump.
25% increase in volume over stock oil pump.
Same as the 10555 with the addition of grooves machined in the body and cover. The grooves reduce cavitation effects in high RPM applications.
Includes intermediate shaft with steel guide.
Uses both 3/4” bolt on or press in screen.
Using this oil pump will reduce pressure at idle.
The 10555C uses the high pressure spring only.
Racing Applications Only.
Patent No. 5,810,571



10990

High volume performance upgrade for the M-99HV-S.
Increase in volume of 25% over stock oil pump.
The 10990 is a Big Block style oil pump made to fit the Small Block applications.
The drive and idler shafts have been extended to allow for additional support in the cover. Additional support eliminates dynamic shaft deflection at increased RPM levels.
The cover is doweled to the pump housing to assure alignment of the shaft bores.
The relief valve has a screw-in plug instead of a pin.
The housing and cover are CNC machined and phosphate coated.
An additional spring, the original stock replacement is supplied which will reduce bypass pressure if needed.
Includes intermediate shaft with steel guide.
Uses 3/4” press in screen.
Patent No. 5,810,571.


10990C (Anti-Cavitation)

High volume performance upgrade for the M-99HV-S.
Increase in volume of 25% over stock oil pump.
The same as the 10990 except with the addition of grooves machined in the housing and cover. The grooves reduce cavitation effects in high RPM applications.
Using this oil pump will reduce pressure at idle.
Includes intermediate shaft with steel guide.
Uses 3/4” press in screen.
Racing applications only.
Patent No. 5,810,571.




GM B.B. Performance Pumps


10770

High volume performance upgrade for M-77HV.
25% increase in volume over stock pump.
The housing and cover are CNC machined and phosphate coated.
The lower pressure spring is included to reduce pressure if desired.
Includes intermediate shaft with steel guide.
Uses 3/4” press in screen.



10774

10774Standard volume performance upgrade for M-77.
The housing and cover are CNC machined and phosphate coated.
The lower pressure spring is included to reduce pressure if desired.
Includes intermediate shaft with steel guide.
Uses 3/4” press in screen.




10778

High volume performance upgrade for the 10770.
Increase in volume of 25% over stock oil pump.
The drive shaft has been manufactured from chrome-moly steel.
The drive and idler shafts have been extended to allow for additional support in the cover. Additional support eliminates dynamic shaft deflection at increased RPM levels.
The cover is doweled to the pump housing to assure alignment of the shaft bores.
The relief valve has a screw-in plug instead of a pin.
The housing and cover are CNC machined and phosphate coated.
An additional spring, the original stock replacement is supplied which will reduce bypass pressure if needed.
Includes intermediate shaft with steel guide.
Uses 3/4” press in screen.
Patent No. 5,810,571.


10778C (Anti-Cavitation)

High volume performance upgrade for the 10770.
Increase in volume of 25% over stock oil pump.
The same as the 10778 except with the addition of grooves machined in the housing and cover. The grooves reduce cavitation effects in high RPM applications.
Using this oil pump will reduce pressure at idle.
Includes intermediate shaft with steel guide.
Uses 3/4” press in screen.
Racing applications only.
Patent No. 5,810,571



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