reason for my low oil pressure?

[Accordtheory]

Recently, I, with the help of a friend, installed another stock short block in my 87 turbo. (I shattered one of the pistons) The guy I bought it from said it only had like 70k on it, but I think he was full of shit, because it only has like 40-45 psi oil press at 80mph, and only slightly more than 10 at idle. (With 20W50) I used my old oil pump, pickup tube, oil filter housing, and oil control nozzle thing between the block and the head. With my old short block, I would have 20 idle/60 psi cruise with 10W30. WTF? is there anything other than main and rod bearings that could be causing this? When I start the car, the gauge creeps up very slowly to full press, around 70 psi when cold, when it used to jump up very quickly. This engine's code is BS instead of A20A3, now I know what that stands for, BULL SHIT... If any of you guys have any ideas, let me know, thanks

[Chadroper]

A worn oil pump maybe if the clearence between the inner and outer rotors is too much. Other than that worn main and rod bearings can cause low oil pressure. Also if the bearings do not fit tight enought there will be excessive clearence and oil will be thrown off the bearing and lower oil pressure. Excessive valve train wear in the rocker arm shafts and camshaft bearings might lower it too. Is the pickup tube distorted or blocked, its very close to the bottom of the oil pan so if thats bent it will cause oil starvation? The block could have blockage in the oil passages. Also did you damage the oil control thing. I know the oil pump is driven by the timing belt. Does it have enough tension that its spinning it properly?

[HondaBoy]

which block was it from, the carb or fi? although i dont think that would matter about the oil pressure. that does sound like you may wanna check out your bottom end if the top is fairly new/rebuilt. im sure the other guys will know about something.

[Chadroper]

Look at your oil. If there are metal shavings or pieces of brass colored shavings then the bearings are failing. When they fail from fatigue the bearing inserts flex and crack. These cracks enlarge until pieces of the insert stip away from the steel backing.

[Chadroper]

One way that you can find out what is causing it is to dissassemble the block and look at the bearing inserts. If they have places where the bearing is crumbling they have failed from fatigue. If they look polished they were oil starved. Misaligned bearings can cause that. The steel backing can turn blue if they get hot enough.

[shepherd79]

the problem can be with oil you are using heavy oil 20w-50. switch the oil to 10w-40 and if it still does it, replace the oil pump.

[TINBOAT]

Slow oil pressure build up can come from alot of different things, but most common is the pressure by-pass valve in the pump stuck open, or a worn out pump. Worn out rods and mains are the next culprit, but a bottom end knock at warm idle would be noticable.

Also, if you have a mechanical oil pressure guage, you have to bleed the air out of it at the guage to insure proper readings. (air in the line compresses, oil does not)