hey i have a 71 chevelle wit a 454 bored 40 over i believe. i just recently bought the car and i have noticed that the oil presure runs at about 30 when cruising and at idle it will drop to 5 or almost nothing. i have knee knocker gauges in it. not original. this is after it warms up of course. when frist cranked it runs about 60 then as it warms it gets lower and lower. any one can help me i aprecaite it. thanks alot.

mine is doing the same darn thing, can't figure it out. i'm thinking of getting a new gage and sending unit to see if it is just a gage problem.

i am running mobil 1 but it was doing that before i swithched.

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71 Chevelle SS clone 454 th400 Ford 9" 395hp/435tq at the wheels
79 Z28 under construction...

put sending unit on front of block may need oil pump or cam bearings at leased

cam bearings? y would i need those? i was thinkin oil pump but i cant understand y it would get less presure as it warms unless there is maybe a presure release valve gettin stuck or something. when the oil warms and thins it may not be closing enough to keep the presure up but when its cold the oil is thick enough to keep presure. this is just my stupid idea any thoughts?

by the way i'm already runing 20w-50 synthetic castrol.

my race car oil pressure started doing crazy things put new pump in it checked out every inch of the motor put it back in same thing cam bearing had gone bad my motor man said it can & does happen the bearing would slip in block after motor got warm and cause the trouble changed bearing & cam fixed it

i am unfamiliar wit this cam bearing. how can a bearing slippping have anything to do wit the oil pump. i am a beginer at mechanics so if u wouldnt mind explainint that thanks.

my sending unit is on front of the block 4 TRUE oil pressure. it is the best place 2 get it . it will let you know of ANY problems in the oil systems it wont have any thing 2 do with the pump just the pressure if your having any oiling problems it is at the (end) of the oiling systemif a bearing slips or goes out the pressure will fluquate up & down or be irritic and it is eazyer to deteced and you will hopefully fine it be4 any majour motor damage happens

Oil pressure is mostly determined by bearing clearances. Think of it like a garden hose. If you put your thumb part way over the end the water comes out at a higher pressure. Take your thumb away and the pressure goes down. If any of the bearings are loose, as in wide clearances, the oil will just spill out all over the place and your pressure will go down.

My knee knocker oil gauge states psi between 50 and 60. I think that thats too high, do you guys concur?

307 cid

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Joe G.
ChicagoChevelle68
Any car past 1972 is just simply transportation, really!

Mine reads 60 all the time on my 454 this is reading were the original unit came, right by the filter

what bearings and cam are we talkin bout? are we talkin bout in the pump. i dont know if htere is a cam in there or not hahaha. thanks for your help.

<BLOCKQUOTE>quote:</font><HR>Originally posted by jpete:
Oil pressure is mostly determined by bearing clearances. Think of it like a garden hose. If you put your thumb part way over the end the water comes out at a higher pressure. Take your thumb away and the pressure goes down. If any of the bearings are loose, as in wide clearances, the oil will just spill out all over the place and your pressure will go down.<HR></BLOCKQUOTE>

For the sake of accuracy when you put your thumb on the end of a water hose and partially close off the orifice the water comes out at a higher VELOCITY and a reduced PRESSURE. The water upstream of your thumb is flowing at a higher PRESSURE and a reduced VELOCITY. On either side of your thumb flow is the same.

The problem with oil pressure is that with increased bearing clearance there is a larger void to fill (downstream of your thumb) oil pressure will drop as the oil passes from proper clearance to loose clearance. You are correct about the oil being slung away from the crankshaft. As the bearing wears the oil begins to have more escape area between the bearing and the corner radius of the crank journal(s).