Additional Oil Cooler 1975 2.7

[niall]

Has anybody out there put an additional oil cooler on a 2.7.

My 2.7 only has the standard engine mounted cooler. When I'm driving it hard it seems to get a bit hot.

I considering installing an oil cooler sandwich plate at the filter mount and installing a decent 19 row oil cooler.

Any advice.

Thanks
Niall

[ossiblue]

Niall,

I just finished installing an OEM 28 row brass cooler in the front of my 75 2.7. I used stock porsche hard lines, thermostat and flex lines. It works like a charm, never exceeding a hair over 180 on the temp gauge. I must say, however, that I haven't driven yet in hot SoCal summer temps, but I expect much lower temps than without the cooler. I suspect that you, living in Ireland, will not have to be too concerned with extreme temps, even in summer. My feeling is it was money and effort well spent to keep the engine happy.

Larry

[Grady Clay]

Niall.
That probably isn’t a suitable solution. It might work OK on a non-dry sump engine but not well on a 911 in the scavenge circuit.. A front cooler absolutely mist have a safety pressure relief valve and should incorporate a thermostat.

Your first project could be to install the pieces for an 11-blade, 245 mm diameter, fan with a fan pulley of 80-84 mm and a crankshaft pulley of 134 mm diameter. This gives a fan-to-crankshaft ratio of 1.82:1. In your climate and altitude, that might even negate the necessity for a front cooler.

If you plan vacation trips from Tunis to Cairo, you will need substantial front coolers in addition to the fan upgrade.

If you decide you need/want a front cooler, the set of parts from a 911SC or Carrera are the easiest to install. You should use a fan cooled full-fin cooler (late Carrera or high quality aftermarket). The thermostat assembly includes the proper pressure relief valve. You will find a lot of info here.

Best,
Grady

[B Goode]

Hi Grady,

I understand the need for a thermostat, but why is a pressure relief necessary? Is that to short the circuit back to the oil tank should the cooler clog up?

Also, would you trust an aftermarket thermostat if the opening temp was right? What size AN fittings and hose would you trust to be big enough?

Sorry for the barrage of questions. I appreciate your advice.

Thanks,
Kyle

[Grady Clay]

Kyle.

The issue with the pressure relief valve occurs during cold start-up after the 911 has set overnight or longer. The crankcase is full of cold oil so the scavenge pump pumps 100% oil into the scavenge (front cooler) system. During normal operation, the front cooler flow is about 60% oil and 40% air.

During this cold start-up, the cooler can be overpressured (in the absence of a pressure relief valve) and lead to failure. This becomes painfully apparent if you put a full-fin cooler in place of the “trombone” on a ’73 911S or Carrera 2.7 RS. These are the only cars without a pressure relief valve.

Every 911 front cooler system (except ’73) has a pressure relief valve. ’69-71 and race cars it is a separate component. In ’72, both the pressure relief valve and thermostat are in the oil filter console. Starting with ’74 it is integrated into the thermostat assembly ahead of the right rear wheel..

Even the race cars, where every gram is paired off, have a pressure relief valve.


Chuck Moreland at Elephant Racing can probably answer your aftermarket question better than I can.

Best,
Grady

[niall]

There is a sandwich plate available with a built in relief valve / internal bypass valve, this is to reduce pressure in the cooler when the oil is cold. It is not a thermostat, so I suppose it would be wise to avoid very high revs until oil is hot.

Would the sandwich plate system with built in relief/bypass valve work?

Niall

[niall]

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