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I have a sbc 1970 4 bolt main block. Engine has about 25k miles. .060 bore, flat top speed pro forged pistons, molly rings,edelbrock 7102 cam,doug herbert lifters, clevite cam,main @rod brgs. I use havoline 10w40 oil. I would like to
know what is normal oil pressure. Cold at idle (850) and hot
at idle. also at kruzz about (2400). :confused: Comments :welcome: :welcome: As always hotrodders buliten board :thumbup: :thumbup:





jim dandy
 

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10 psi per 1000 rpm is enough when hot. If you're getting 24 psi at 2400 rpms, you're good. Normally from brand new, they made a bit more than that.

When cold, expect them to spike the blowoff valve at about 60-70 psi at fast idle. Cold idle at 850 I might expect 20 or more.

That's all assuming my oil pressure gauge is accurate :)
 

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curtis73 said:
10 psi per 1000 rpm is enough when hot. If you're getting 24 psi at 2400 rpms, you're good. Normally from brand new, they made a bit more than that.

When cold, expect them to spike the blowoff valve at about 60-70 psi at fast idle. Cold idle at 850 I might expect 20 or more.

That's all assuming my oil pressure gauge is accurate :)
CURTIS 73

I really apreaciate your swift reply, You've made my day :)
And as always hotrodders BB is :thumbup: :thumbup:


jim dandy
 

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Lot's of people ascribe to the 10 in 1000 rule... but that is too low.

We have a 93 company truck with 150,000 miles on a 5.7 and it idles at 45 hot and runs 55+ down the road.

Rebuilt 350s have a notorious problem of crappy oil pressure even with very tight clearances. If you want good oil pressure, bush those lifter bores to .001 clearance.
 

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xntrik said:
Lot's of people ascribe to the 10 in 1000 rule... but that is too low.

We have a 93 company truck with 150,000 miles on a 5.7 and it idles at 45 hot and runs 55+ down the road.

Rebuilt 350s have a notorious problem of crappy oil pressure even with very tight clearances. If you want good oil pressure, bush those lifter bores to .001 clearance.
I really doubt you will ever find a GM engine that has .001 lifter bore clearance as we have new GM lifters and new GM blocks and we have found them around .002 right form the factory and using these parts have never had any problems with oil pressure but we line hone every block that goes through our shop and we check cam bearing bores for clearance and we do find a lot of them over the high side and on these ones we blue print bore the cam tunnels to blue print as GM line bore the cam tunnel with the bearings in place on stock type blocks.
 

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xntrik said:
Lot's of people ascribe to the 10 in 1000 rule... but that is too low.

We have a 93 company truck with 150,000 miles on a 5.7 and it idles at 45 hot and runs 55+ down the road.

Rebuilt 350s have a notorious problem of crappy oil pressure even with very tight clearances. If you want good oil pressure, bush those lifter bores to .001 clearance.
Pressure is measured before the lifters most times on a SBC. Lifter leakage should not affect readings. I've bent and broken pushrod and rockers and even valve causeing the lifters to jump clear out of the bores without losing oil pressure. In fact, One engine ran 48 of 50 laps and 7500rpm that way. Engines are going 9500 with 35# these days. 15 at idle and 45 would be all you need plus a bit more IMO.
 

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SBC oil pressure

Concensus is that the lifter bores cannot be that tight. OK, I concede. Need to be .002, and round obviously.

How about that distributor housing? That could be quite an oil leak since it seals one side of the engine.
 

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johnsongrass1 said:
Pressure is measured before the lifters most times on a SBC. Lifter leakage should not affect readings.

I've bent and broken pushrod and rockers and even valve causeing the lifters to jump clear out of the bores without losing oil pressure.

In fact, One engine ran 48 of 50 laps and 7500rpm that way. Engines are going 9500 with 35# these days. 15 at idle and 45 would be all you need plus a bit more IMO.

You must have had a gallery restricted engine. I think our emphasis is on street/strip engines.

Old Smoky insisted that the pressure be measured at the END of the gallery at the lowest pressure point if you are running 10/1000.
 

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xntrik said:
You must have had a gallery restricted engine. I think our emphasis is on street/strip engines.

Old Smoky insisted that the pressure be measured at the END of the gallery at the lowest pressure point if you are running 10/1000.
Yeah, that's true, I forget that sometimes.

We don't restrict engines anymore. The oil is used as a top end cooler to extend valve spring life.
 

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The biggest thing is, getting the oil there. Once there, the rotation of the crank does all the wedging work. Stock Oil pumps pump prolly 3 times as much oil as actually needed. So minor leaks around the lifters and dist, really don't matter to a hill of beans.
 

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My engine with a high flow oil pressure pump
Cold it will hold 50PSI and hot is drops between 40-45PSI with a mechanical gage, thats with 20w50 I will drop back to 10w40 the next oil change.
The motor has about 6000 miles on the rebuild.
 

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johnsongrass1 said:
The biggest thing is, getting the oil there. Once there, the rotation of the crank does all the wedging work. Stock Oil pumps pump prolly 3 times as much oil as actually needed. So minor leaks around the lifters and dist, really don't matter to a hill of beans.

If pressure didn't matter engines would still be splash oiled like a model T.

Sure pressure delivers the volume to the bearings, but sufficient dynamic pressure at each bearing surface helps maintain the wedge. High loads will allow contact if pressure is insufficient.

As I said, our 93 350 company truck has 150,000 miles on it and idles at 45 and hits 57 (by the gauge) at about 2200.

I am still asking this question after many years....... If Chevy 350/5.7 assembly line engines idle at 45-50 and make 55-60 at 1800 rpm with 5w30 oil, then why is it that rebuilt hot rod engines set up to minimal clearances have low oil pressure problems? :confused:
 

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Pressure is just the next best way to measure volume. No one has a volume meter. I didn't say it doesn't mean anything...it's just more pressure doesn't mean more bearing protection. As long as enough volume is there.


You already know the answer to that question. Stop twisting it around. Your Work truck has no more problems than any other engine. You gotta remember things like platigauge inacuracies, questionable assembly at the bearing, cams bearings off size, Cams journals off size, worn out part's deemed in good shape, all these things contribute.
 

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I bet your looking at factory gage in that old work truck. My experience is the general doesn't make very good gauges. And if you look in a factory service manual under oil pump specs, you will see that normal oil pressure at a hot idle is around 10+ psi.
 

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johnsongrass1 said:
Pressure is just the next best way to measure volume. No one has a volume meter. I didn't say it doesn't mean anything...it's just more pressure doesn't mean more bearing protection. As long as enough volume is there.


You already know the answer to that question. Stop twisting it around. Your Work truck has no more problems than any other engine. You gotta remember things like platigauge inacuracies, questionable assembly at the bearing, cams bearings off size, Cams journals off size, worn out part's deemed in good shape, all these things contribute.
LOL....... :rolleyes: :rolleyes: :rolleyes:
 

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OK you guys have me wondering something. I have not been able to keep my SBC from leaking. Being from Florida and knowing how hot this motor has ran before I have always ran thicker oil. I have had to practically glue the valve covers on and the oil pan wont seal for the life of me. I have been told that the oil pump in the motor is a high pressure high volume pump. Could I be blowing the seals out of it? Things I have noticed, the biggest oil leak seems to be at the front and rear oil pan seal, the sides seal just fine. Followed by the valve covers and then the dip stick. The valve cover leak has been fixed but the oil pan requires me to remove the motor to fix it so it will have to wait. But its getting replaced by a one piece gasket from summet. I don't drive the car very often so thats fine. But I would like to stop oiling the road and everything under the hood every time I drive the car. Could this be due to the thicker oil? Going to drop back to 10w40 with some STP when I do the next oil change and see the leak slows down. :(
Oh I also notice that the electric gage and the mechanical gage are off by about 3 psi. I have the electrical gage in the inside and a mechanical gage mounted by the motor that I believe to be accurate. It reads higher.
 

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Jake_Dragon said:
OK you guys have me wondering something. I have not been able to keep my SBC from leaking. Being from Florida and knowing how hot this motor has ran before I have always ran thicker oil. I have had to practically glue the valve covers on and the oil pan wont seal for the life of me. I have been told that the oil pump in the motor is a high pressure high volume pump. Could I be blowing the seals out of it? Things I have noticed, the biggest oil leak seems to be at the front and rear oil pan seal, the sides seal just fine. Followed by the valve covers and then the dip stick. The valve cover leak has been fixed but the oil pan requires me to remove the motor to fix it so it will have to wait. But its getting replaced by a one piece gasket from summet. I don't drive the car very often so thats fine. But I would like to stop oiling the road and everything under the hood every time I drive the car. Could this be due to the thicker oil? Going to drop back to 10w40 with some STP when I do the next oil change and see the leak slows down. :(
Oh I also notice that the electric gage and the mechanical gage are off by about 3 psi. I have the electrical gage in the inside and a mechanical gage mounted by the motor that I believe to be accurate. It reads higher.
One piece rubber pan gasket YES... never had one leak. :thumbup:

Oil pump blowing seals....... NO.... theoretically there is no pressure in the crankcase to blow the seals. Is the pcv working? When you pull the oil cap off and rev the engine, is there oil vapor coming out? If there is, then the ring blow by is pressurizing your crankcase and blowing the seals. You must step up to a vented oil cap.

Oil viscosity is determined by ambient temperatures, stress the engine is doing, and engine clearances/ bearings /pistons, etc.

10w40 should be adequate below 90*. STP has zinc anti wear additives in it to help older flat tappet engines.. You might consider an engine oil labeled "racing" which has the wear additives in it that have been left out of new grade oils for smog purposes. You might also consider Shell Rotella T in 15w40 for your crankcase. It seems to be the choice now for flat tappet engines.

Pressure gauges. There is no way to tell if either one is correct. If they read 40-60, just go with the it. It is only relavent if they read 10..... :D
 
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