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low engine pressure

3K views 14 replies 7 participants last post by  docvette 
#1 ·
my engine pressure is around 40-50 when i start it up the it drops to about 35 while its heated,and im driving...but when im at an idle im around 10-20...
and if i do a fat burn out after the burn it will drop to almost 0 and it will sometimes stall out.
wat would cause this?
could it be my oil pump?
the engine was just built and im not to shure what it is?the mains should al be good and stuff so im so out of the loop on this...
could t be cause if i have a leak in the intake manifold?
 
#2 ·
Sounds like you have too much clearance in some of your bearings. If your clearances are too wide, you will have low oil pressure. Did you replace the cam bearings when you rebuilt it?
I have similar pressure in my 350, but it has many miles on it,
 
#4 ·
Lots of things can contribute to low oil pressure. however, most gauges aren`t accurate below 10 PSI, some aren`t accurate below 15 PSI. you should at least have 10 psi oil pressure per 1000 RPM. Oil gets thinner as it gets hot, this is why it`s higher at start up when it`s cold. I`ve been driving my car a long while now and when it`s hot it`s often the oil pressure goes to 0, but I keep a ear on the engine, if I don`t hear any lifter clattering, or any death rattles, I don`t worry about it any, as I keep in mind it`s not accurate below a certain point. and no, a intake leak wouldn`t cause low oil pressure. 20 psi at idle is fine.
 
#13 · (Edited)
oil pressure

Well, I would start with a manual gauge. Look along the side of the engine block and you well find a plug that goes in to the oil passage (make sure it is the oil and not the water passage) If you can't find one remove the oil sender unite and screw a flex line into it and attach a pressure gage (0 to 60 lbs.) to the other end. start the engine and check the oil pressure in this manner. You know at idle and then reve it up to say 1500 rpm. and so on. If the oil pressure is more to the liking or it has a big deference, then may be the sending unit is bad. Also it could have a small chip from the overhaul in it. And that would make for a faulty reading.
Here are a few other thing that I seen happen: New Short block and OLD oil pan. When the old engine let go it knocked the baffle plat lose in the oil pan. So they welded it back in place before they reinstalled it. After reinstalling the engine it would have oil pressure at idle and then when you revved it up and held it there for a very short time the oil pressure would full to almost 0! After about third. R/R of the oil pan they discovered that the baffle would hold the floating oil sump up when installed, just at the top of the oil level. At idle it would get enough oil to show pressure on the gauge, But at high RPM's. it couldn't keep up and showed a very low to 0 oil pressure.
This one was almost the same thing but it had a fixed oil sump pipe and screen. They somehow had bent the oil sump pipe up just enough that it would not pick up the oil and so it had 0 oil pressure. Someone said DID YOU PUT ENOUGH OIL in it? The answer ----Y! but then he put two more quarts of oil in the crank case, and it had real good pressure.
Any way just thought I would shear them with you. Check it out never know what will work! -------------------Gene Neal
 
#14 ·
More of the same answers that you already have, I have an old beater truck that has a oil pressure gauge instead of idiot light. When it's cold,the oil pressure is great but when it's warmed up, goes to near zero at idle. I was kinda concerned at first, but I was told by gearhead much smarter than me if I had any pressure at all at idle, no rattle and it picked up with RPM not to worry. That has been at least 4 years ago. 45 second burnout? Anything is possible with that kind of thrashing. Good luck
 
#15 ·
Doc here, :pimp:

Like Gene Neal said..

In a Deep pan (or any for that matter) Without Baffles oil will slosh away from the pump pick up...

As far as the stalling..

That much abrupt Change in G force, could be anything in the Fuel delivery system or induction system..Also too, remember too, the throttle mechanism is slamming home everytime you do it..you may need a vacuum assist dash pot. (or run a real high idle..)

Doc :pimp:


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