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ljibis ljibis is offline
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Join Date: May 2007
Posts: 26
Just a few more data points for you...

I have a '77S with a rebuilt 2.7 - backdated exchangers, no reactors, 11 blade fan, stock "trombone" oil cooler. I've been driving it back and forth to work (25 miles one way) in 80-85 degree temps.

At highway speeds (65-85 mph) the oil temp runs right around 185, climbing to 200-210 in stop-n-go traffic. With airflow it always cools back down to around 185.

A few things to check...

Oil lines - they may be clogged or pinched somewhere, and not getting full flow to your front cooler.

Timing, both mechanical and ignition - this can have a big affect on temperature. The ignition timing is decently easy to check, but mechanical not so much (it involves an engine drop). If either is off the engine can "hold in" extra heat. My buddy's 78 930 was running 20-30 higher temps than normal because his mechanical timing was off just a bit.

Fuel mixture - is it running rich or lean? This can be checked with a CO meter, or have someone else do it. Rich running will lead to cooler engine temps, while lean running leads to hotter engine temps. If you are running the stock CIS this would be a good time to thoroughly check out the system, then check the mixture.

Internal oil thermostat - hard to get to (engine drop again), but it can be checked. This is also a very common point for these engines to leak, so there is a good "while you're in there" seal replacement job you can do. My buddy and I recently checked one by filling a deep sauce pan with enough vegetable oil to cover the t-stat, dropping in an electronic cooking thermometer, and then heating it up. Be careful if you do this as the oil expands a lot as it heats!!! You can watch the thermostat open at the approx. 180 degree point if it is functioning correctly. These can fail...I suppose they get jammed up with crud over the years.

I'm sure others will chime in with ideas. Good luck, be careful!
1977 Porsche 911S
Guards Red/Cork, no sunroof, no flares!
Old 06-21-2007, 10:41 AM
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