psears

Hello,
I was wondering if anyone has any idea why my newly rebuilt 3.1 liter 911SC motor is running too hot. I don't know exactly how hot, since I have the standard factory gauge without degree measurements, but after about fifteen minutes of freeway driving, the whole engine compartment seems very hot, and the rear bumper gets very hot as well. The (Weber carburated)engine is being broken in right now, with only about 50 miles on it. The oil level is about 3/4 of the way up the dipstick marks, which is probably a little high for break-in, since it smokes a little at start up. I live in Texas, and it is around 100 F now. I heard that the ignition timing can affect the motor temperature, especially during break-in. Any thoughts?

Thanks!
psears@austin.rr.com

Bill Gregory

If you look in the temperature gauge from the right side (use a flashlight), and on the edge of the gauge outside the line of sight, you'll see the temp markings in centigrade that the gauge was calibrated to. Normal running temps are 180-210 degrees F, with 250 degrees F/121 C being the hottest you want to run at. If your temps are up, a lean (vs rich) fuel mixture can contribute to that, in addition to half a dozen other things.

Dial 911

The rear bumper gets hot for good reason...the muffler is directly under it!

Matt Chamblin

The first thing you need to do is replace the non-numbered gauge in your car. I thought my car was running way hotter than it really was. After I installed the new gauge it revealed I'm not even reaching 220 F on hot days. And I live in an area where it regularly reaches 100+ in the summer. The gauge kit is less than $100 from Pelican and well worth the peace of mind. And it only took 20 minutes to install.

Steve Weiner-Rennsport Systems

Psears:

Good advice from the other folks here about installing the gauge with numbers. There is nothing quite like having accurate information,......

Aside from that, make positively sure that your ignition timing is spot-on. Advanced or retarded timing is very bad for cylinder head temps, especially the latter!!!!

Make sure that your jetting is correct for your engine configuration. Slightly rich is much preferable to being slightly lean, right now. Do a few plug cuts to see what's happening in there.

During this critical phase of engine operation, you sure don't want the heads and cylinders to run hotter than they already will during break-in.

Make sure that the distributor's vacuum retard and advance (if so equipped) is operating correctly and that you have 35 deg total advance at 6000 RPM.

Try not to let it run at 210 deg or more during break-in. If you gotta park it during the heat of the day, then so be it. This will ensure a long and healthy life for your new engine.

Good luck!

JBH

After running the car for a bit, just do a quick check under the right fron wheelwell to ensure your loop cooler is functioning.

The oil thermostat (the one under the right rear wheelwell) can fail and require replacement.