I have a 1966 442 with a small block 400. We rebuilt the engine last year and now have about 800 miles on it. It seems that the oil pressure has been dropping over the last 2 months. When the car is cold it runs just under 50lbs. Driving runs just under 30lbs and at a idle it is about 12lbs. I replaced the oil filter and changed oil, oil looks good and doesn't smell burnt. My gauge is not factory and I have put a T in so that I still have the idiot light. Does anyone know what the oil pressure of this engine normally runs?

 

when you say rebuilt, does that mean all new bearings and everything? Was the pressure good for the first 799 miles? If so what if anything has changed recently?

 

Don't know what your oil pressure should be, but my 1971 Cutlass 350 motors (with mechanical oil gauge & T fitting for idiot light) oil pressure runs low when warm at idle (maybe 5 psi), about 30 psi on the highway, and 50 or so at start up when cold. I think I read somewhere that Oldsmobile motors just don't have the best oil pressure, one reason why they wont rev as high as a Chevy. My car has run at these pressures for the last 5 years since I got it back on the road, with no problems

 

Thanks for the replies! With the rebuild it got new bearings along with a heathly list of other parts. I have not changed anything since then, I really started noticing the pressure change after getting it out of winter storage. That was about 100 miles ago.

 

And you changed the oil/filter then, right? Are you using a different kind of oil than previoiusly? I always look for changes, what was different from then to now. It doesn't always help but........As AggieOlds says, Oldsmobiles do run a little lower on the oil pressure than Chevies, especially at idle. It is because the tolerances are a little looser than chevies. I have read horror stories about Oldsmobiles being rebuilt the same way chevies are with their tight clearances and then the engines fail because of that. Haven't personally experience that though, just heresay.

 

I did change oil after running the rebuilt engine in the garge before it hit the street and then I changed it shortly after getting out of storage. I have been running Napa 10w30 and have been using Napa Gold oil filters. I understand what you mean about looking for changes, I just can't think of anything different since last year. As an engine breaks in will the pressure drop? I am also thinking about getting another gauge just to rule out that or the sensor.

 

Well yes, pressure will drop as tolerances loosen up. As I have read, the main and rod bearing tolerances especially determine oil pressure, the tighter the tolerances the higher the oil pressure can be, that makes sense to me. As to how many miles are required to see a significant drop, I can't say. I really wish we could get a response from a machinist/engine builder, that would be the most definitive. I think you have a good idea about trying another guage, is your present gauge direct sensing or remote? The direct sensing guages are the most accurate but then you have to run your oil line into the passenger compartment, it is best to use rigid line in place of the plastic stuff many gauges come with. You probably already have done that. Well, good luck!

 

Dan -
Thanks for all the replies. I am running an electic gauge and was thinking I might pickup a mechanical just to see the differance.
Todd