'77 2.7 7R Case oil pump question

[racer_X]

I recently ran a DE with my 77 2.7 and was told that even though I have a rebuilt 2.7 with the necessary updates (line bored, divilar studs, oil tensioners, 11 blade fan, etc) that I may not have a sufficient oil pump. The engine ran 210 F and was holding 1 bar or so per thousand rpm while on the track.

Can someone point me to information or tell me more about the oil pump differences between the 2.7 engines, the early mag engines and later aluminum engines?

Thank you in advance,
John

[stownsen914]

Do you mean 10 psi per 1000 RPM? 1 bar/1000 RPM would mean 6 bar or a little more at your engine's redline, which seems high.

Most will tell you that bigger/later oil pumps are better. I don't want to debate that here, but I'd say if you are getting 10 psi per 1000 RPM, you should be fine.

Scott

[cmcfaul]

low temps like that on the track...you are fine

Chris

[racer_X]

So if I understand correctly: there isn't a scavenging issue that I can run into when operating the car repetitively at 4,000 to 6,500 rpms (as long as the temps are 210 or less)?

I may be off with the oil pressure, my gauge reads in in/lbs of oil pressure. When it's 210F at idle it is at the first heavy mark. At 3,000 rpm, it is in between the 20 and 60 mark. At higher rpms I am not exactly sure but it seems to go up exponentially.

[cmcfaul]

never heard of a scavenging issue (dry sump). Porsche engineers are pretty smart and the engine design ever evolving. 210 is a great temp for running on the track, Temp directly effects oil pressure. If temps are low oil pressure should be fine. If temps hit the 250 mark oil pressure will read close to zero at idle. That's a concern. You are fine.

[tharbert]

In 76, PAG incorporated the "oil bypass mod" so that "when the 76.8 psi limit of the oil pressure RELIEF valve is achieved, excess oil pressure is routed back into the inlet to the pressure side of the pump rather than going into the bottom of the case."

Coinciding with the modification, PAG modified the oil pump by reducing the scavenger side and increasing the pressure side. These are the 4 rib pumps. The 76 4 rib Mg pump was eventually changed to aluminum. It's my understanding the 4 rib Mg and Al pumps were identical inside. I read here recently that the aluminum pumps are preferred for rebuilds presumably because Al wears better. Maybe a guru can fill us in here.

If you have Wayne's book, there's a section about the different pumps along with pictures. Tom Butler posted this awesome photo showing the pumps and the years they were used:

[chris_seven]

I believe that 210degF would tend to be the high end of acceptable.

195 is what I would consider ideal and a temperature within +/- 5 degrees would be good.

Bearings are running about 75degF hotter than the bulk oil temperature and will start to melt if they reach 375degF.

At 250 degF the bearings will be around 325 degF and their life will reduce significantly.

The more you can reduce the crankcase pressure on these engine the better as the windage will reduce significantly with the density of the oil mist.

Any power loss due to windage will heat the oil and these effects can be substantial at high revs.

Windage is normally considered to be proportional to the square of the rotational speed so high revving engines will be quite badly affected and

The only way to improve the performance of 911 engines in this respect is to use a pump with a 'better' scavenge section.