I have a'46 Chevy Pick up and it has a '58 235 straight six in it. I just got this truck and have an odd problem. When the engine is cold I am getting 30 pounds of pressure but as it warms up the pressure goes down to 0.
It did have some gas in the oil so I replaced the fuel pump (bad diaphram) and changed the oil to straight 30 weight.

Supposedly, the motor was rebuilt about 1,000 miles ago.
It runs well and I have one more local show to go to then I'm going to take it apart for some painting.

I would really appreciate any help.
Gary

 

try thicker oil, maybe the engine was rebuilt with the original oil pump

 

Hi gporter,

Welcome to the Chevy Forums.

Unfortunately, we have no idea (very possibly you don't either) how the engine was rebuilt.

There's no legal parameters as yet for rebuilt parts and engines governing quality control, but sight unseen, and the oil pressure is so low, I think we can assume that either the engine was merely R&Red using new gaskets and a few minor components, OR someone was sleeping at the switch for the QC tests.

As an engine gets steadily older, oil pressure tends to drop with age, as long as it doesn't dip below 20PSI generally people don't get too excited.

A replacement oil pump may help a little, but I would keep expectations low. Even if it works 100%, you may still only see 15-25PSI on an engine that old.

 

Thanks for the replies. I am waiting for a new oil pump. The motor looks good. No bearing damage and everything is really clean. I'll post the results