Technical oil pressure question

i have a question in regards to oil pressure, im running a rebuilt small block with a meling high volume pump, the problem im having is extremely low oil pressure at idle ... 2-4 lbs and under a load its at roughly 25lbs
my gauge is an auto gauge mechanical. all bearing clearances are perfect but low oil pressure remains..... ideas?

 

missing a plug somewhere?

Faulty distributor housing?

 

well... i have a "cold" # 1 cylinder but the rest work great

 

First, try a second gauge, that is the cheap thing to try initially. That pressure is pretty low.

Don

 

ill try that thanx

 

If it were me, I'd hook up a direct reading gauge.

 

Depends where you are reading it,front or back of the block or oil filter, they will all vary some.My guess is you have left out a plug in the front by the cam.I would also look to make sure the lifter in number one cyl. is still in, that would bleed off oil pressure real quick.
Did you block off the oil filter by-p***, any restricters in it?

 

first and cheapest, change the oil filter

 

1/2" plug under the rear main cap installed? I've also seen stuck open byp*** valves in the oil pump.

 

I have seen that more than once and bad gauges

 

Were the cam bearings replaced ? Everyones concept of the word overhaul could include a lot of nothing.

 

yup its there

 

yes everything was replaced, bearings plugs from top to bottom

 

Whats the oil pump to oil-pan clearance like? if its too close it will starve the pump

 

check your oil pump, I know dropping pan ****s, but there is the byp*** plunger, some are pressed in, some are held in with cotter pin, if the plunger has moved where its sticking out of the pump it can cause severe oil pressure drop quickly. Had one shear the pin and drop to oil pressures like that.

 

I recently had this same problem on my 351C. It was a quart low on oil. Added a quart and pressure at idle became normal again.

 

If you didn't tap and put threaded plugs in the oil galley plug holes (at each end of the block), it might've pushed out one of the press in plugs behind the timing chain gear. I had it happen, years ago and it had oil pressure similar to yours.

 

o.k.,you say the bearing clearances are perfect.... what is "perfect" and how did you measure them ?
Had a guy build an engine with perfect bearing clearances, he bought a crank kit but it was a -.020" under crank, with -.010" bearings. (on the main bearings) had oil pressure cold, (40 PSI+/-) but went away quick with temp, didn't make any noise, sounded fine. he said he "checked them" too..I'm just sayin'

 

I second SQUIRREL
A friend of mine had a NEW one that was loose on the block and dumping the pressure. Foreign made, I think.

 

I need to ask a question here , Is a late model 350 block ? I have had two of my engine rebuilds with low oil pressure . Took forever to find the problem. In the lifter valley GM had drilled three bolt holes for the roller lifter retainer (spider). the holes were drilled too deep and got into an oil p***age. Had I used an original roller cam and lifter set up the bolts would have filled the holes. But I used an old school flat tappet cam and didn't fill the 3 bolt holes . Simple fix was three bolts and a drop or three of anaerobic sealer on the threads. Experience is a lousy teacher...test first. .lesson comes later.