Ibfurloughed

At what point do you worry about oil pressure at idle? I recently woke up an "XCH" LS7. Still tuning and tweaking so I only have a couple of short 10 minute drives on the car which is a 1973 t-top 4sp. Initial cold start oil pressure is what I would expect 60+ psi on factory pressure gauge at idle. After car gets up to temp idle oil pressure drops to just 17-18. A small blip of the throttle and the oil pressure climbs back to the 50's as expected.

I have always liked 25 psi at idle and anything less to me signaled a tired motor with worn bearing clearances. I have to admit I don't remember what oil is in the car right now. I drained the oil which was 15 years old before I started it the first time and just put something cheap in not knowing if it was going to even start. I think I should start by putting a better, heavier oil it to see what happens. So, what is a good readily available oil for an old solid lifter cam motor? And how low would you let hot, idle oil pressure get before you had serious concerns? I have bandaged up old tire motors with a Melling hi flow oil pump before but not sure if that's a good idea on this engine.

hugie82

The fast and easy bandaid is use a heavier weight oil, Lucas oil stabilizer or tip your idle up a bit. Personally I like to see over 25 psi at idle and 40-45 while cruising down the highway.
This will keep you going until you decide when a rebuild is in your future as long as you don't have any knocking at idle. The LS engine has the front pump that can be replaced but since you are reading good high pressure when revved, I would lean towards bearings being opened up or the pump gyro gears are worn. A smal chance the pump gears are out of alignment but that's a slim chance that's your problem.

MelWff

so you have no idea what viscosity oil you put in the engine?
try Valvoline VR-1 10W30, silver bottle. I'm sure others will suggest something else.
Hopefully you changed the oil filter and used a "good" one?

LT-1 kid

when ever I see 10 to 18 psi at hot idle, the motor gets pulled and at least
gets new bearings.

TimAT

If that engine has the correct oil pump GM installed, you should see 50-60 psi hot.

TimAT

Hugie-- not to rain on your parade, but this is a BB LS-7. not one of the new LS series SB's..

427Hotrod

First...hook up a manual external gauge to verify for sure what it has. 17-18 psi isn't terrible....of course depending on the oil you're using. Might try a little thicker if the pressure cks out. I wouldn't worry about it...but I'd cut the filter open when you change the oil to verify nothing bad is happening. That's a sweet motor and we want to keep it alive!

JIM

toobroketoretire

Any time you suspect low oil pressure verify it with another gauge of known accuracy. Although the Bourdon Tube movements are quite accurate there is always the possibility of the needle slipping on the shaft which would give low pressures at cold and hot temperatures.

7T1vette

Stock GM oil pump with engine at factory-set idle rpm could have as low as 10 psi. Normal is 12-15 psi at rated idle.

The STOCK engine didn't really need higher oil pressure at idle, so the GM engineers decided to save engine 'work' and fuel by running a different pressure schedule than some folks like. 10 psi for every 1000 rpm was the 'rule of thumb'.

If you don't like that, change out the regulator spring to raise it. Or put in a big HI-FLO pump that will take a lot of engine power when at idle.

For a 'normal'-use engine, the GM/Chevy engineers have proven their design wisdom over many decades with successful V8 life and performance.

toobroketoretire

The 425" Oldsmobile engines only had 25 psi when cruising.

bashcraft

The 425 Olds also had oil starvation problems at higher RPM's.

Big2Bird

The LS-7 was a race engine only sold over the counter. It did NOT have a stock oil pump. TimAT knows, he has an original one.

Indiancreek

Normally these symptoms are what you suspected. a clearance issue. Verify with another gauge like has been said, if you really want to know, drop the pan and mic a main and a rod to see the clearances and bearing condition.