oilpressure at Idle

[bezerk]

What should the oilpressure be at idle with hot oil?

i have a Spa electric oilpressure sender wich is located in the fitting of the stock sender of the oilpressure gauge...

20w50 was used the first 700 miles, and oilpressure at idle wAS ABOUT 20 psi on the spa gauge...(stocker is in the middle)

now i use 10W30 and oilopressure at idle is 15psi (stocker is between the 1/4 and 1/2).

please tell me this is save...

 

[Falco]

Well. The expeienced guys will tell you it depends on a lot of things.

First of all where do you measure this pressure?

I've a freshly built engine, I'm using 10w40 and and the port of the remote oil filter house I can see around 45psi when truck is hot, idle around 900 RPM.

HTH,

 

[bezerk]

Well. The expeienced guys will tell you it depends on a lot of things.

First of all where do you measure this pressure?


HTH,

have a Spa electric oilpressure sender wich is located in the fitting of the stock sender of the oilpressure gauge...


what does your stock gauge read at idle?

 

[GM TURBO]

What I've read from GM is that they require 9psi to run - which seems very low to me. Your numbers sound a bit low. Is this a fresh motor?

 

[bezerk]

when truck is hot? you mean water temp, or drove it for about on hour?

thanks

 

[bezerk]

yes this engine is brand new, has about 800miles on it...

when it's cold it gives me about 40Psi at idle, i can thin that when the eninge is hot it should be 1/2 cause of the thickness of it...

at 4K rpm it's about 60PSI (hot)

so so 60PSI /4 is about 20PSI at 1k RPM<= is this a good way of thinking?

 

[Christian Dionne]

10psi per 1k RPM is the old small block rule of thumb.

Most 4.3 trucks I've seen (tons of em) have had hot oil pressure near the half mark which is 40psi, but that's including 200k mile 20W-50 trucks too.

I think anything over 20psi hot idle is overkill, alot of TurboBuicks only get 10-15 psi hot idle.

 

[bezerk]

10psi per 1k RPM is the old small block rule of thumb.

Most 4.3 trucks I've seen (tons of em) have had hot oil pressure near the half mark which is 40psi, but that's including 200k mile 20W-50 trucks too.

I think anything over 20psi hot idle is overkill, alot of TurboBuicks only get 10-15 psi hot idle.

half mark is more like 25PSI if you ask my SPA gauge.

i think you eased my mind..

more input is appriciated.

 

[4C FED]

:flash:

 

[sofaKINGfast]

10psi per 1k RPM is the old small block rule of thumb.

Good rule........

 

[myclone]

10psi per 1k RPM is the old small block rule of thumb.

Most 4.3 trucks I've seen (tons of em) have had hot oil pressure near the half mark which is 40psi, but that's including 200k mile 20W-50 trucks too.

I think anything over 20psi hot idle is overkill, alot of TurboBuicks only get 10-15 psi hot idle.

Turbo buicks use a way diff oiling set up than the 4.3 though. As a matter of fact the LC2 is one of hardest engines to get what I like to call "comfy" oil pressure out of (comfy=Im ok with it).

Anyways, the oil pressure you see isnt so much a function of the oil pump itself but the stiffness of the bypass spring(s) as well as bearing clearance and oil weight in GM engines of our vintage.
A geneneral idea of what youll see:
stock bypass+stock oil pump+fresh motor+30w= ~35psi hot idle
shimmed bypasses+Z28 oil pump+fresh motor+30w= 45-50psi hot idle
Z28 pump+100k mile motor+40w= 35psi hot idle (SBC)

There are multiple things I didnt list as well as multiple combinations that will affect the above numbers also so use the above as a general guide not as chisled in stone "thats the way it is period".

To address your issue it is my opinion that the oil pressure is a little low BUT.... it could be due to the type oil pump used, bearing clearances, shimmed/not shimmed bypasses, etc. To sum it up your oil pressure isnt in the scary range but it isnt too awfully far from it either for a fresh rebuild IMO. Need more info on what is in the bottom end of your motor to say for sure.

 

[myclone]

10psi per 1k RPM is the old small block rule of thumb.

Good rule........

Yeah, for a bone stock normally aspirated SBC with 2:73 gears that will never see the high side of 5k RPM. Forced induction/high performance/heavy duty street engines will NOT live happily ever after with 50psi oil pressure at 15psi of boost and 5k RPM. The noise you hear soon aftwords is the sound of the rods beating their way out of the engine via the oil pan and/or block due to a lack of oil film between the rod bearings and crank journal.

If youre building a SBC for a beater/low hp application then 10psi per 1k rpm will work. Try it with a street motor that see abuse/boost and you'll drive over the crank in a pretty short time span.

 

[bezerk]

içantr imagine that my Stock gauge is so much off compared to my SPA, maybe my SPA sender ain't good..

everybody says that 1/2 of the stock gauge is around 40PSI, where my SPA gauge says 20 :-? .

Maybe i should measure it with a different gauge at the remote port?

 

[myclone]

içantr imagine that my Stock gauge is so much off compared to my SPA, maybe my SPA sender ain't good..

everybody says that 1/2 of the stock gauge is around 40PSI, where my SPA gauge says 20 :-? .

Maybe i should measure it with a different gauge at the remote port?

It would probably be to your advantage and piece of mind to get a measurement with a mechanical gauge. SPA gauges are electrical and use a "sending unit" to translate the actual pressure into an electrical signal so you very well could have a bad sending unit or at least one that is inaccurate.

 

[bezerk]

gonna give it a try tonight..

 

[Falco]

The stock gauge and sender is a POS. I can see the needle around the 3/4 mark, when hot at idle.

As Dave said double check it with a mechanical gauge. I've done this and it verified the readings on my autometer gauge.

Later,

 

[bezerk]

well, i checked with a mechanical gauge and it seems to be that the SPA is accurate enough...

here is what i don't get...

Maximum oil pressure should be 80, so how can you have 40 at idle??
i mean, that with 2K rpm it's already 80...

 

[bezerk]

annything i can do, to make it higher? maybe one of the Bypasses is bad?
if it is, wich one?

i have cut open my oil-filter and can't see annything bad..

 

[myclone]

dammit

 

[myclone]

well, i checked with a mechanical gauge and it seems to be that the SPA is accurate enough...

here is what i don't get...

Maximum oil pressure should be 80, so how can you have 40 at idle??
i mean, that with 2K rpm it's already 80...

With 80psi at 2k RPM hot then you are ok as the low idle pressure may very well be due to bearing clearances being on the loose side.

Just be sure to keep an eye on the oil pressure and watch for any significant changes for a while and if the engine doesnt have any other issues I wouldnt be affraid to stand on it.