3.0 Oil pressure question

[lyonsfin]

I have an 83 911 SC with about 130K miles. Top end rebuilt properly by expert about 2k miles ago. The oil pressure was reading low. Replaced pressure sender twice, replaced gauge, checked relief valves, changed oil and filter. I have driven about 1k miles including highway runs and a HPDE. Car runs great and performs great. The idiot light never comes on (except when turning on ignition). The needle goes up to about 3 bars and then jumps down. When warm, it goes to about 2.5 bars and does the same thing. It is as if it is hitting a stop and bouncing back down. I am thinking bad wire or gauge issues?

[LakeCleElum]

No worries....2.5 bar=about 35 lbs.....Rule of thumb is 1 bar per 1,000 rpm? ...........Before I replaced my 2.4, it idled at ZERO on a hot day...I think you are fine. What's the oil temp? That plays a big part of all this......

[maui44]

My 77 911S has had a long-block done by a top notch wrench and the pressure is running about what yours is. Are you running 20/50 oil?

[lyonsfin]

I switched from a synthetic to Castrol 20W50. I have the car in Savannah, GA so it is hot. At idle it is right down to almost nothing, but no matter how high revs are it hits the ceiling at 2.5 - 3 bars. Normal driving it is about 2 bars. Cold it will idle between 2 and 3 and will run close to 3 until warm.

[Reiver]

I don't know. I have an 83 sc with 223k miles and no rebuild at all...I get 3.5 bars in 110 degree weather after a long drive @ 65/70 mph 5th gear. Never goes to 3 bar at speed. 1 bar at idle on the hottest days. 20w50 oil. I've never seen 2.5 bar at speed.
Gauge or sender if you have a good rebuild and it is properly broken in with seated rings.

[Daviboy]

Lyonsfin,
I have an 82 SC which had 150,000 miles prior to a complete engine rebuild about 2,000 miles ago. Since then the oil pressure reads +/- 1 bar at idle sometimes 3 bar if cold dropping back to 1 when at operating temperature. As I accelerate through the rev range my pressure increases almost in line with the rev counter i.e. 2,000 rpm 2 bar, 3,000 rpm 3bar you get the picture. I think your gauge is reading normal oh and BTW I run 20w50 in all weather.

[T77911S]

Originally Posted by maui44

My 77 911S has had a long-block done by a top notch wrench and the pressure is running about what yours is. Are you running 20/50 oil?

my 77 idles at around 15-18 psi. i know the idle is not that critical, but i have always had confidence in the bottom end because of this.


i have heard 10 psi per 1k, not 1 bar. but.... porsche played around with the oil pumnps over theyears. they were always changing the scavange to pressure ratio's. that is why the 77 idle pressure is or should be higher than the older cars.
(i dont know the years they changed pumps, but it is in bruce andersons book if interested).

[Daviboy]

Did not know any of the 74 - 89 cars had an oil gauge in PSI mine is Bar for sure 1 bar = 14psi...