Why do SC's have such high oil pressure

sd_iconoclast

Registered User
I just rebuilt the engine in my SC. I also installed an Autometer mechanical oil pressure gauge. I was very surprised to find that the gauge reads about 28 PSI at idle, 35 PSI at 1000 RPM, 55 PSI at 2000 RPM, and it tops out at 70PSI. All readings are when the engine is warm.
From other posts, I have learned that these readings are normal.
I have also noticed that the oil pressur appears highly damped. It falls slowly when the engine speed drops.
All my other cars show a little over 10 PSI per 1000 RPMS and the oil pressure follows the engine speed as if it were the tachometer.
Does anyone know why the SC has such high oil pressure or why the pressure changes so slowly?
PS I am using 5w30 castrol synthetic oil.
 
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its like asking how the positrack on the rear end of the plymouth works....It just DOES:D

actually i have no idea

leaving it to the pro's;)
 
Be happy the oil pressure is higher than 10psi at idle. Rule of thumb is for every 1,000 you need at least 10psi. Rod bearing failure is quite common in SC's so I wonder what would happen with a different pump?
 
I know that bearing clearances on these motors are pretty tight. I know with a supercharged application it is good to have higher pressure down low because of how fast they build power down low. Combine this with the oil pump on them, and you may find your answer. I have a high volume oil pump on my car, but I don't have a oil pressure gauge to get a accurate reading from. Every engine can technically be different also.

Chris
 
Also keep in mind the amount of load the blower puts on the crank bearings, especially at the front, so the higher the oil pressure the better.
 
I just rebuilt the engine in my SC. I also installed an Autometer mechanical oil pressure gauge. I was very surprised to find that the gauge reads about 28 PSI at idle, 35 PSI at 1000 RPM, 55 PSI at 2000 RPM, and it tops out at 70PSI. All readings are when the engine is warm. QUOTE]


When I hooked up my electric (Cobalt) Autometer oil pressure gauge I was surprised to see 90 lbs. of pressure at start up and 80 lbs when cruising along. I'm getting anywhere between 40 and 60 lbs at idle - it jumps around due to cam lope.

eddie
'90 5-speed SC
'97 LX sport
 
WhiteThunder, If you're seeing that high of oil pressure, then you need to take the thick oil out and start using 10w-30 as your highest viscosity if you aren't already.

Excessive oil pressure costs horsepower, so I opened the clearances up on the mains to get rid of that high oil pressure. I see 25lbs. at hot idle and 55 at WOT.

I've always followed this chart and it's dead on. One of my race car motors has a 3.25" main journal, running 7500rpm, and is a bitch to keep bearings in it.
 

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Regarding the slow movement of oil pressure: Is the Autometer gauge liquid filled? It might have a damping effect. Have you used this specific gauge on another car so you have something to compare?
 
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WhiteThunder, If you're seeing that high of oil pressure, then you need to take the thick oil out and start using 10w-30 as your highest viscosity if you aren't already.

Excessive oil pressure costs horsepower, so I opened the clearances up on the mains to get rid of that high oil pressure. I see 25lbs. at hot idle and 55 at WOT.

I've always followed this chart and it's dead on. One of my race car motors has a 3.25" main journal, running 7500rpm, and is a bitch to keep bearings in it.

This is the gauge I'm using for oil pressure - the full sweep job.

http://www.egauges.com/vdo_mult3.asp?Type=Elec_Engine_Pressure&Series=Cobalt&Units=E

Yes, I'm using Mobil 1 15-50

I also have matching Autometer gauges for water temp., volts, and boost/vacuum.

eddie
'90 5-speed SC
'97 LX sport
 
I have a Cobalt boost gauge, too. I'm wanting to get the oil pressure and water temperature gauges then fit them into the factory cluster.

I think I saw pictures of yours done, a bit ago.
 
If you think those numbers are high, mess around with a Ford modular engine sometime. 90 psi at idle on cold startups with 5W30 is the norm.

-Rod
 
I have a Cobalt boost gauge, too. I'm wanting to get the oil pressure and water temperature gauges then fit them into the factory cluster.

I think I saw pictures of yours done, a bit ago.

The photo is in this thread ... http://www.sccoa.com/forums/showthread.php?t=94060&highlight=gauges

I looked at trying to put the gauges in the stock locations, but didn't want to tear my hair out working around the printed circuit that's on the back of the instrument cluster.

The volt gauge is turned so I can easily spot the needle when it's at 13 to 14 volts, through the steering wheel.

The way I ran the wires for the gauges through the OEM rubber-plugged hole behind the driver's kick panel, behind the left front wheel splash guard and into the engine compartment - all the wires had to be extended by about two feet to reach.

eddie
'90 5-speed SC
'97 LX sport
 
Ford has traditionally taken oil pressure right after the oil pump where as Chevrolet and some other manufactures take it off the camshaft bearings or somewhere farther away from the oil pump.Hence our readings tend to run somewhat higher.
 
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