1973 Oil Pressure Concern
07-21-2003, 06:57 PM
#1
Addict
Rennlist Member
Rennlist Member
Thread Starter
1973 Oil Pressure Concern
I have 500 miles on my new top end rebuild (the jugs were not pulled nor the case split).
Yesterday, I took a long drive and noticed that, when I had the car at 210-220 F, the oil pressure was 20 psi (at 3-4000 rpm). In the past, it would be 30-40 psi. On cold startup I see about 60-70 psi.
Some more facts. My wrench refilled the car with 15W-40 oil while I have used 20W-50 in the past. Also, I had him install Carrera Tensioners. In my 1973, the pressure sender is on the same line as the right hand cam tower line/tensioner supply line.
Do I have a problem? Should I be concerned?
TIA
Yesterday, I took a long drive and noticed that, when I had the car at 210-220 F, the oil pressure was 20 psi (at 3-4000 rpm). In the past, it would be 30-40 psi. On cold startup I see about 60-70 psi.
Some more facts. My wrench refilled the car with 15W-40 oil while I have used 20W-50 in the past. Also, I had him install Carrera Tensioners. In my 1973, the pressure sender is on the same line as the right hand cam tower line/tensioner supply line.
Do I have a problem? Should I be concerned?
TIA
07-22-2003, 05:59 AM
#2
Rennlist Member
Sounds like typical oil pressure experiences in a 911 of this vintage, I think. My old '73 behaved the same way with the Carrera tensioners and lighter oil. My '79 SC did, too, until I updated to the 964 style of cam oil line adapters and banjo bolts (the adapter and bolt where the oil lines attach to the camshaft/rocker housing. Now, I run Mobil 1 0W-40, and I still get 3.0 bar at 2,000 rpm, even when the oil gauge reads in the middle (around 210 Fahrenheit, I believe).
I would just go by what the book says for the oil pressure, and not worry about what you see when it's hotter. You'll find lots more information about this if you do searches here and on Pelican.
I would just go by what the book says for the oil pressure, and not worry about what you see when it's hotter. You'll find lots more information about this if you do searches here and on Pelican.
07-23-2003, 05:50 AM
#3
Burning Brakes
Harry,
I think the book says approx 50 psi @ 4,500?
I have a '76 and have the Carrera tensioners and have run the car on Mobil 1 for years. At low revs, when hot, (up to 2,500) I see about 15 psi. At tick over even lower, but at 4,500 she's running at about 50 psi. I'm told this is pretty normal.
PJC
I think the book says approx 50 psi @ 4,500?
I have a '76 and have the Carrera tensioners and have run the car on Mobil 1 for years. At low revs, when hot, (up to 2,500) I see about 15 psi. At tick over even lower, but at 4,500 she's running at about 50 psi. I'm told this is pretty normal.
PJC
07-23-2003, 06:34 AM
#4
Rennlist Member
One more thought, which may have occurred to you already. With the change to CIS (that's what you have, right?), Porsche relocated the oil pressure sender from the front of the main oil gallery, right at the pump discharge, to the rear, which is downstream of all of the galleries to the crankshaft, plus the piston squirters. If you add in the loss of back pressure with the change to Carrera tensioners, then you're looking at a potentially much lower oil pressure reading than you'd see in the earlier cars. In my understanding, flow is more important than pressure for engine lubrication.
07-23-2003, 08:25 PM
#5
Addict
Rennlist Member
Rennlist Member
Thread Starter
Originally posted by Tom Frisardi
One more thought, which may have occurred to you already. With the change to CIS (that's what you have, right?), Porsche relocated the oil pressure sender from the front of the main oil gallery, right at the pump discharge, to the rear, which is downstream of all of the galleries to the crankshaft, plus the piston squirters. If you add in the loss of back pressure with the change to Carrera tensioners, then you're looking at a potentially much lower oil pressure reading than you'd see in the earlier cars. In my understanding, flow is more important than pressure for engine lubrication.
One more thought, which may have occurred to you already. With the change to CIS (that's what you have, right?), Porsche relocated the oil pressure sender from the front of the main oil gallery, right at the pump discharge, to the rear, which is downstream of all of the galleries to the crankshaft, plus the piston squirters. If you add in the loss of back pressure with the change to Carrera tensioners, then you're looking at a potentially much lower oil pressure reading than you'd see in the earlier cars. In my understanding, flow is more important than pressure for engine lubrication.
My Transmitter is located adjacnet to the blower fan (I get confused about front and back). It is on the oil line to the cam tower that also feeds the tensioner. I think that this, combined with the lighter oil is causing the lower readings not some fundemental problem.
07-26-2003, 06:00 PM
#6
Addict
Rennlist Member
Rennlist Member
Thread Starter
Saw my wrench yesterday. He listened to the engine and inspected his work. Had a second fellow review the same. Conclusion? Most likely a combination of my reused transmitter, the transmitter location, lighter oil, and the new pressure fed tensioners all make it appear like my pressure is low. Not to worry.