Hi I am Dr don. I have a 1975 nova with a 1975 olds 455 cid. I did a trade for it. Upon starting to get it running I found that the engine was totally plugged up I started with all new pushrods lifters new rockers, were worn so the rocker was hitting the valve spring retainer. I spun a rod brg while trying to locate a lifter noise. Didn't exceed 1500 rpm. Took the pan down and found all the rod brgs were half crystalized. I replaced the rod and crank brgs anf just put in new cam brgs with a new RV cam. I have had a low pressure problem since day one. When the eng is cold it runs great. when it reaches operating temp the oil pressure goes down to about 10 lbs. touch the throttle and it's totally responsive. I can't drive over 50 mph cause the lifters start to mane a lot of noise. When warm the pressure doesn't go over 20 lps and drops to 10 when stopped. I run 20/50 oil with stp. it puts the zinc back in the oil. I just put a high volume oil pump in. No difference from when I first put all the brgs in to now. All the brgs were tempered and crystalized and the #5 cam brg had no cam marks on it. the others were half used on the bottom the top of all weretemoered and not tuchin the cam I have flushed the eng 4 times and it is totally clean. Is there a torque for the oil pump I feel something is letting the oil squeeze out when it's thin. I am a retired A S E master tech and put almost 50 years in the trade. Any one have a clue

 

I think 10 warm is not far from how they came. the drain back on these is critical to be open so the oil does not sit in the valve covers and starve the rest of the engine. It would be nice to see more oil pressure but that is not far from normal

 

Did you have the crank turned when you replaced the spun bearing? If the motor was torn down, are you sure the oil gallery plugs were reinstalled?

 

Welcome. I moved your thread because the "Site Help" subforum is for questions about the website itself.

10 PSI warm is low but not fatal at idle. At highway speeds it should be closer to 40 PSI. Did you change the oil pump when you had the engine apart? Did you check bearing clearances?

 

Welcome to the site. I am sure this can all be sorted out several good suggestions so far.

 

That would be my guess too!