low oil pressure problem

[fnoblitt]

i got a 350 with about 1000 miles on it since the rebuild. oil pressure at start up is 50lbs. going down the highway, warmmed up is about 45lbs . when i come to a stop guage says 2lbs. as soon as i start moving, it goes back up. is this normal ?

 

[FS87LT]

What about at hot idle in "N" at about 700rpm or so?

 

[carhead22000]

if you have 2lb at idle,id say something wrong.have a look.

 

[COPO]

At idle mines 25 psi using 10w40 oil. I think it was 25 psi with 5w30.

 

[CorkyE]

You should hear the lifters ticking pretty loud with only 2lb of pressure.

 

[sandlapper]

if the gage is verified & true --- I'd be looking at the oil pump pickup tube; it may be loose in pump & Not securely press-fitted --- once you have pump in hand, correctly reposition strainer height AND tack the tube to pump body.

I'd also verify relief valve & spring in pump are moving freely & Not sticking. A tiny bit of grit/schmutz in there can wreak havoc.

also possible pump strainer is too close to pan; so close that when at hot idle it cannot suck enough oil quickly enough into pump. Closely inspect strainer to verify wire mesh is clean & not heavily varnished. Maybe it wasn't properly cleaned; they're most often replaced as they're not so pricey. FYI, Melling has lotsa Very good good tech articles & videos. Easily understood & acted upon.

Melling Oil Pump Screen Installation Process - Melling

This video demonstrates the correct installation procedure of a Melling press in oil pump screen to the oil pump. For a full step by step document to accompany this video, please see www.melling.com

www.melling.com

Some folk routinely reuse pump without first closely inspecting inside of pump; doesn't always work out if the pump's scarred up inside.
So if, that is IF you replace pump. Suggest upgrade w/ std vol & std pressure later M155 (repeat M155 Not M55) melling. Call melling tech (8:00am-4:30pm EST Monday-Friday 517-787-8172 EXT: 2601) & tell them exactly which pan you have and they will advise exactly which pickup part number you'll need to fit your pan & M155 pump. M155 has improved efficiency & stability at Low-to-Mid rpm.

FWIW --- '93 camaro w/ 350 uses melling M155 pump & 155S pickup --- both total about $52 at RA --- a good value IMO.

 

[fnoblitt]

i had an autogauge mechanical oil pressure gauge, but the the plastic line/ ferrells kept leaking. so i put a jegs electric oil pressure gauge. i put a new m55 oil pump and a new pickup 1/4" off bottom of pan and tack welded in place when i put the short block together. the pan is a dorman replacement that has a small drip going on at the rear seal area. i'm running valvoline vr1 40w oil to keep the 268 cam happy.

 

[GoldenOne7710]

Which port on the block is the oil sender plumbed into? The port right above the oil filter typically will show a little more PSI on a gauge vs the port on the back left top (behind the intake). Remember it only takes 7 psi to turn off the "dummy light" a lot of Camaros had.

Any idea what the bearing clearances were for the mains? Rod side and bearing clearances? If it was assembled "loose", then you may have to run heavier oil.

 

[fnoblitt]

the line is plumbed to the top of the block rear of intake, the machine shop did the basic short block so i don't know the bearing specs. i may just put a m155 pump on when i remove pan to fix the leak

 

[1980RS]

What were the bearing clearances on the engine? You could always add a HV pump with low oil pressure. I've done that in the past on SBC's and it fixed things right up with better oil pressure.