low oil pressure

-
DARTLARRY

DARTLARRY

Well-Known Member
Joined
Mar 19, 2007
Messages
563
Reaction score
217
Location
FORT WAYNE IN
stock LA360 with a small cam, and headers. The oil pressure when cold is never over 45psi, when warm it is at near zero. I replaced oil with 20w50, in hopes that it would increase some pressure, it may be 10psi when warm now, still never increases above 45psi no matter the rpm. Next step replace oil pump, if the bearing clearances are creating the issue I don't want to pull pan in car and change pump. Ay thoughts?
 
just a guess but my first thought was a weak relief valve spring in the oil pump . or the relief is hangin open or the pickup screen is plugged . could be many other things also .
 
What is the overall condition of the engine? Do a compression test to see, if the oil
pressure is the only issue then... pump or bearings.
 
does the engine knock or rattle on start up .if it does the bearings could be a issue
 
compression is good, it does have what I suspect is lifter noise at start up...I guess it could be bearings.
 
If the bearings are worn you could probably get away replacing the pump with a HV pump until you have the $ to do a rebuild. You could replace the main & rod bearings but if the cam bearings are worn bad it has to come out.
 
I was going to replace the pump with a HV pump for now, then replace the engine or rebuild later. I am enjoying finally driving, and don't want to tear down too much, or pull right now. Replacing the pump would be a winter project for me.
 
DARTLARRY said:
stock LA360 with a small cam, and headers. The oil pressure when cold is never over 45psi, when warm it is at near zero. I replaced oil with 20w50, in hopes that it would increase some pressure, it may be 10psi when warm now, still never increases above 45psi no matter the rpm. Next step replace oil pump, if the bearing clearances are creating the issue I don't want to pull pan in car and change pump. Ay thoughts?
Click to expand...
As said confirm the readings first with another gauge. If the readings are accurate, and the pressures never exceed 45 psi regardless of RPM, then it is very probably the pump.

BTW, there are 2 relief spring pressures: one at 55 psi and one around 72 psi. So you could have the lower pressure spring and a -10 psi error in your gauge across the range, and both the pump and bearings be A-OK.
 
DARTLARRY said:
stock LA360 with a small cam, and headers. The oil pressure when cold is never over 45psi, when warm it is at near zero. I replaced oil with 20w50, in hopes that it would increase some pressure, it may be 10psi when warm now, still never increases above 45psi no matter the rpm. Next step replace oil pump, if the bearing clearances are creating the issue I don't want to pull pan in car and change pump. Ay thoughts?
Click to expand...
post a picture of the engine, believe it or not...it really helps in direction of attention.
 
DARTLARRY said:
compression is good, it does have what I suspect is lifter noise at start up...I guess it could be bearings.
Click to expand...
Could be pistons too.
To get an idea how worn out it might be, I like to grab the lower side of the belt near the alternator and my other hand on the fan...and rotate it both directions till I feel the crank grab the timing gear 'slack spread' if it's a ton of movement between ...then its toast. The chain being toast usually leads to bits of nylon gear clogging the pickup screen and low oil psi. It starves.
The silent chains they used in most production vehicles is too blame..and lack of maintenance in changing them every 80k
 
1499629266646.jpg
 
I was having the same issue with what id say is a very similar engine. I did the 20w50 with about the same result. A new HV oil pump and I have lots of oil pressure.

Cley
 
Larry; factory oil pressure is 45 - 65 PSI . So you are good there. Factory idle oil pressure is 8 psi minimum for a 1976, but is different for earlier model years [?]. -------- run it -------
 
pt70 said:
Larry; factory oil pressure is 45 - 65 PSI . So you are good there. Factory idle oil pressure is 8 psi minimum for a 1976, but is different for earlier model years [?]. -------- run it -------
Click to expand...
Oil light came on below 12psi in my 71 swinger
 
from the little I know about this engine and seeing the picture of how pretty painted it is...In my day, we would call these things "Krylon Motors" which is an old motor reslapped together with gaskets changed 'or not' freeze plugs changed 'maybe' new timing chain 'sometimes' ..but either way, it was never new or rebuilt ....was just an original 40+ year old engine from a van stuck into an a body..

I am not saying I know that's what the OP has, merely suggesting the possibility.
I myself wouldn't wanna set myself up for a tow bill by assuming the motor is fine as.
I'd change the pump, pull a cap bearing while I'm there..
 
Lifters click and clack, rods will knock. When you pull the pan, a bad rod bearing will move back and forth on the crank journal maybe just a little or a lot depending on bad the bearing is spun.
 
Hmmm. I am having the same problem - only I know that the engine is new/fresh and all the clearances are checked and rechecked. Everything is new. Has a new Melling HV oil pump, drive gear/shaft and pickup. I have checked the pressure with two different gauges - same result. I have come to the conclusion that it could be ; the oil pump relief, a filter pressure relief (2 different filters - going to try a wix gold next) or maybe perhaps the oil pickup is too close to the bottom of the pan????
This is really bugging me! The motor is ALL fresh, balanced, new +.040 KB pistons, scat rods, standard crankshaft, new comp cam, lifters, pushrods, etc. The block was thoroughly cleaned as was the crank.
Does anyone have ANY idea???

Flummoxed!
Cheech 14
 
cheech14 said:
Hmmm. I am having the same problem - only I know that the engine is new/fresh and all the clearances are checked and rechecked........... 14
Click to expand...

So what are they?? Did you write them down?? How were they measured?? Plastigague or with real measuring devices?? Meaning Micrometers, Dial bore gauges, snap gauges.

Did an oil gallery plug get left out?
 
Oil galley plug left out somewhere is #1 suspect.
What type of lifters?
Stock oil pickup or what?
 
ch1ll said:
Lifters click and clack, rods will knock. When you pull the pan, a bad rod bearing will move back and forth on the crank journal maybe just a little or a lot depending on bad the bearing is spun.
Click to expand...

Better hope they`ll move back and forth , up and down = a diff.story
 
You must log in or register to reply here.
-

Back
Top