283 V8 looses oil pressur at driving temperature
 

I am about to acquire a 283 out of a 66 chevy pickup.To put in my 67 C10. It was recently (overhauled) by a previous owner. The oil pressure is good at low to medium temperature, but at running temp. it drops to near zero. My thoughts are #1. Main bearings to much clearance. #2. Cam bearings to much clearance. #3. I don't know if the oil pump was replaced or even checked. I will tear the engine down and check these items. Any further ideas on the the cause of this problem will be appreciated. Thanks in advance.

Re: 283 V8 looses oil pressur at driving temperature
 

Sounds like a possible bad pump. whatever it is, I would stay away from it unless you are buying it under the idea that it is going to need an immediate rebuild? Must be priced accordingly. free?

Re: 283 V8 looses oil pressur at driving temperature
 

what are you relying on to give you correct pressure reading? what are the pressure readings?

Re: 283 V8 looses oil pressur at driving temperature
 

Could be all the above, and it could be the wrong weight oil too. Ask the guy if the mains were plasti gauged when rebuilt and see what he says, i cant remember the clearance off hand but i think about .001 to .0015? If he rebuilt it doesn't know then he has no business rebuilding an engine in the first place. If he has no answer on the plasti guage he could have probably just slid a new cam into the old bearings too. I don't know the guy obviously but this is what i'd be thinking.

Re: 283 V8 looses oil pressur at driving temperature
 

As stated see what the real pressure is and it's normal for oil presssure to drop off after reaching running temperature. Mine reads high when first cranked up but after she is running it will drop off a bunch around 25-40PSI. Get a good trusted reading yourself.

5lbs of oil pressure is not un common at idle. ;):chevy:

Re: 283 V8 looses oil pressur at driving temperature
 

Most every small block chevy I have ever owned showed low oil pressure at idle after they are fully warmed up. As long as you have at least 5-10 psi, I wouldn't worry about it.

Re: 283 V8 looses oil pressur at driving temperature
 

If it is actually zero that isn't good. I wouldn't install anything with that low of pressure. Too easy to investigate that and figure out a reason while it is out. Likely it is just the pickup screen on the oil pump too high to suck up the oil.

Re: 283 V8 looses oil pressur at driving temperature
 

Try a different oil filter. One of my engines had extremely low oil pressure after it was rebuilt. It had a Fram filter on it. It switched to an ac delco and the oil pressure remained high ever since.

Re: 283 V8 looses oil pressur at driving temperature
 

I have heard that before.

Re: 283 V8 looses oil pressur at driving temperature
 

I remember the machine shop telling me a small block only needs 5psi of oil pressure per 1000 rpm.
I have a new GM goodwrench 350 in my truck and it has 65psi when cold started, stays about 50 when warm and driving, but drops down to 10 at idle when it's hot

Re: 283 V8 looses oil pressur at driving temperature
 

I have been off of the computer for a while, but I want to thank all of you for the help. I will mic. the main and rod journals as well as plasti gague them. I will replace the cam bearings. I will check the oil pickup screen and height, and replace the pump. Once again thanks for the info.

Re: 283 V8 looses oil pressur at driving temperature
 

In the circle track racing world, the rule of thumb is 10lbs per 1,000 rpm. I think you are fine. Clearances are just a little loose.

Re: 283 V8 looses oil pressur at driving temperature
 

OOps. I just reread my original post and neglected to mention, at highway speed (75 mph. on turnpike & 65 mph on secondary Highways ) when the engine warms to normal temp. the oil pressure drops to near zero. Thanks again for all of the input.

Re: 283 V8 looses oil pressur at driving temperature
 

not good at all

Re: 283 V8 looses oil pressur at driving temperature
 

Ok,different problem. Check the oil return galleys and make sure they are not sludged up and restricting the oil returning to the pan. Have you tried checking the pressure with another gauge?