Slowly dropping oil pressure...

I've finally got everything back togeher and on the road!! Except for one small problem that's making me a bit weary.

Long story short, I found a BAD machine shop. I now have a mixture of engine parts from all over, but a motor that runs at 120 lbs compression and 45 psi of oil pressure at start. That oil pressure slowly dwindles down to just about nothing as the motor warms up though. I tried it with 10w30 initially and it dropped extremely low, enough to make me think of using 30w on a freshly rebuilt motor. After driving around for ~30 mins the pressure while running 30w drops to 7 psi. I know it's within the 10 psi per 1000 rpm rule, but I don't like it a bit (expcially when the same oil pump was putting out 17 psi at warm idle with 10w30 before any machine work was done).

My question: Is this normal, will pressure majically reappear? Is there any way to fix this or are the crankshaft and rods just slightly off in dimension?

If it makes any difference, I've got the high volume kit installed (it's got ~10,000 miles on it alone), a 231 block,and 225 crank and rods. The top end is excellent, but the bottom end is worrying me a bit.

 

On a fresh rebuild, I would think you should get at least 60psi (w/standard oil pump) but you have a high vol kit in there so should be more? Something's not as it should be on rebuild. Did you get the new parts list on your billing?

 

well, part of the fun with the shop was their ineptness... I have a crank ground to 20 under on the mains and 30 under on the rods. I personally bought all of the bearings after looking at what the shop did. other than that, the rods were reconditioned at another shop and shoul be good.

 

some high volume oil pumps do operate at lower psi,but in your case you are usieng the same pump as before,right? would say based on this you got some shotty machine work,easy enough to check,drop the pan and plastigauge them,i do this in all of my rebuilds on assembly,better to find out when you are putting the motor together than after,i hate it for you,hope it all works out,may want to check the gauge,it could be faulty

 

would check the gauge. with 30w I have 60+ pressure cold and 25ish at idle warm. that's with high-vol pump and the 50pd spring.


if the oil pressure is low enough, you will hear the lifters clicking.

 

Did you replace the cam bearings? This is often overlooked with a rebuild and can be a source of low oil pressure. I would think if you did not replace them you would have at least as much as before the rebuild.