Low Oil Pressure in my 403 Olds engine

[Dan Bachert]

I just got done restoring my 79 TA with a 403. I had bought a motor and took all the pans off. Everything looked good so I put all new gaskets on it, painted the motor and put it in. Now, I let it warm up and when I got in to take it for a spin, the oil pressure was in the red-5 psi. When I accelerate, the pressure shoots up to about 50-60 psi. When I first start it up, it sounds ok, but as I’m driving it and decelerating, I can hear a rattle in the bottom of the engine. But if I accelerate again, it goes away, but then comes back.
At first, I thought it was a bad oil pump, but I watched your video and it made a lot of sense. I now realize that it’s probably the bearings. Can this be fixed or is it going to be a total rebuild? Or is it just the bottom end? Also, where can I get the parts cheap for a rebuild? Or should I just look for a used 403? 403’s are hard to find, since they were only used on some Olds & Pontiacs from 77-79. I already bought and installed headers and don’t want to change out a lot of parts with a different size motor.
I looked up Summit and they have a rebuild kit for $300 without the pistons and oil pump. Would that work? Or should I replace the pistons? Or does it need machine work? I don’t know what to look for when I pull it apart. Can you give me some tips or refer me to any videos you have on the subject.
Any suggestions would be helpful.
Thanks!

Topic

[Its me]

If your oil pressure is that low, and you hear a bottom end rattle it sounds like you have or are close to spinning a bearing. Will need at least a lower end rebuild.

Good luck.

-Karl

[Author]

Replies