Why don't I have any oil pressure

[lcraig5]

Why do I have only 12 lb oil pressure when enginge temp is at 190 degrees? I have replaced mains, cam bearings and oil pump. Completely rebuilt engine. It is a 307 Chevy 1968

[maxwedge]

Welcome to AF, assuming the gage is correct, also what is it at 2,000 rpms. Many things can cause low pressure, bearing clearances, internal pump clearances, weight of the oil, connecting rod side clearances, are some of the major causes.. All these things must be checked to determine the problem, there is no quick answer for this.

[Blue Bowtie]

How well does the distributor fit the bore in the lifter valley?

[Torch]

You oil pump shaft is driven by the distributor shaft which is itself driven by the cam shaft gear, do all three of these locations look ok, or are the gears nearly worn off somewhere?

[j cAT]

Originally Posted by lcraig5

Why do I have only 12 lb oil pressure when enginge temp is at 190 degrees? I have replaced mains, cam bearings and oil pump. Completely rebuilt engine. It is a 307 Chevy 1968

If the oil pressure is 80psi cold then drifts down to 12psi I would say the crankshaft is worn....did you measure this for excessive wear /clearances.


as stated this could be many things. you will need the spec's and re-open the engine and start measuring the tolerances..


I never liked the CHEVY 307....not very good back in the old days..

[bobss396]

The 307 was an improvement over the 283 for crankcase ventilation and the PCV valve inception. They are nice motors in the 2 bbl version if you leave them bone stock.

I would get a mechanical oil pressure gage and hook it up under the hood just to rule out a bad dash gage. See what it is at idle, I like to see at least 20-30 psi when it is warm.

If you just drive it around and have no knocks or odd valve train noises, slap a piece of duct tape over the gage and ignore it.

Bob

[72chevelleOhio]

How bout a pick up tube not sealing to the pump. (or a hole in the tube.)

Originally Posted by bobss396

slap a piece of duct tape over the gage and ignore it.

Pfff, a "NOS" sticker.

[j cAT]

Originally Posted by 72chevelleOhio

How bout a pick up tube not sealing to the pump. (or a hole in the tube.)

Pfff, a "NOS" sticker.

as I said before if the oil drifts down to 12psi when hot this is because [most likely] worn engine parts...


If you had low oil pressure at all temps that could be oil pump problems...


I also still think this chevy 307 rebuild is a bad idea...

[slingslingbinks]

Too much clearence on the main bearing's You sure u have the right size installed. Did u plastic-mike the bearings?

[j cAT]

Originally Posted by WarlikeBasil

But i have no idea what men labels are in right now. I heard LRG and Bape and Apes are in is this true.Do men care if they mix labels. Thanks so much in advance for your answers..

please do not foul our forum , with this type of nonsense !

If you have knowledge of these issues you are welcome . If you have vehicle issues , post a your own .

[MagicRat]

Check out the actual pressure with an accurate mechanical gauge, if you do not have one on it right now.

Does the pressure INCREASE as the revs go up?

If yes, then I agree with the above posts. You have worn parts or excess clearances.

Did you machine the crankshaft journals? I have come across engine builders who like to machine tolerances so they are "loose" because this results in slightly less friction and slightly more power. However, you need a high volume (not high pressure) oil pump to get good oil pressure.

Originally Posted by j cAT

I also still think this chevy 307 rebuild is a bad idea...

I wouldn't bother doing so but I've come across a couple of people who are fanatical about originality and have kept their original 307.....

[534BC]

Nothing wrong w/ 12 # oil pressure (at idle)

[j cAT]

Originally Posted by 534BC

Nothing wrong w/ 12 # oil pressure (at idle)

so if you just paid to rebuild an engine, 12 psi of oil pressure at idle or any other operating rpm , would be what you would expect ?

[big dwag]

I've read all of your post, & I had the same problem your having but with a 350 small block. This is what i found to be the problem, Ten of the sixteen lifters had came apart. The clip that holds the top of the lifters in place broke and i found them in the lifter valley, no oil getting though to the front of the motor, On start up it would run at 50 psi and as the motor started to get to temp the oil pressure would start dropping slowly to 10 to 0 psi. I ended up replacing the cam because the rocker arms would make noise, The bearings wore out the crank, Before i changed all of this i was told that the oil pump was bad, So i put a new pump on and got the same thing low pressure. So i don't think the pump is bad because on the inside it just has two gears. So check all of your lifters really good and i bet to will find a couple that are bad. If you cant figure it out bring it to my house i'll fix it.

[j cAT]

Originally Posted by big dwag

I've read all of your post, & I had the same problem your having but with a 350 small block. This is what i found to be the problem, Ten of the sixteen lifters had came apart. The clip that holds the top of the lifters in place broke and i found them in the lifter valley, no oil getting though to the front of the motor, On start up it would run at 50 psi and as the motor started to get to temp the oil pressure would start dropping slowly to 10 to 0 psi. I ended up replacing the cam because the rocker arms would make noise, The bearings wore out the crank, Before i changed all of this i was told that the oil pump was bad, So i put a new pump on and got the same thing low pressure. So i don't think the pump is bad because on the inside it just has two gears. So check all of your lifters really good and i bet to will find a couple that are bad. If you cant figure it out bring it to my house i'll fix it.

the bearings do not wear out the crankshaft. the bearings are very soft metal composite. yellow color. the crankshaft is heat treated steel !

what does happen is with no low oil pressures like 10 psi etc the bearings/crankshaft gets very hot. then the metal treatment is damaged..

new crankshaft and bearings required ! go the cheap way out just bearings you loose !