I think the difference is the calibration of the temp gauge and sender. The 2.7 gauge is calibrated for the 2.7 sender and the 3.2 gauge is calibrated for the 3.2 sender.

I used the '77 2.7 temp gauge with the 3.2 sender and was getting extremely high temp readings. When I installed the 2.7 sender in the 3.2 engine the reading became normal.

I actually encountered the exact opposite result. My '77 (numbered) oil temp gauge showed ridiculously high readings with the 74-76 sender. When I changed to the 77-89 sender (911-606-112-00) my readings normalized and I was able to confirm those readings by conducting a fairly simple test. Check out this thread for my testing details:

http://forums.pelicanparts.com/porsche-911-technical-forum/429344-new-3-2-running-hot-maybe.html

Scott, is it possible that your gauge is actually from a 74-76 car? I'm pretty sure my '77 gauge is original. If you look at the earlier oil temp sender description in the Pelican catalog, it does say for years 74-76 only:

http://forums.pelicanparts.com/uploa...1223736258.jpg

I can only guess that the '77 numbered gauge responds like the non-numbered gauges that came in subsequent years. At least, that's how it appears to me....

Don, great work.

Wow, it looks like a lot of trouble to change from a 915 to a G50. I didn't realize that it would have been that much work and fabrication needed.

+1 on the super work Don. Tony.

I dunno. I believe my numbered gauge is the stock '77 but who knows. I just know I ended up pulling the sender out of the 2.7 engine and installed it in the 3.2 engine to get correct temp readings.