I have a 76 with a L48 350. I just rebuilt with new pistons, Edelbrock perfomer cam, timing chain, intake and carb, fully balanced. I finally have it back in the car and running. Idleing at 8 OTDC. My problem is that when I start it, it immediatly climbs to over 200 degrees but does not over heat. I am wondering if something is wrong with the new temp sending unit or if I have done something drasticly wrong. Can anyone offer any suggestions?

okay.. first.. 200 isnt overheating.

second your new engine will run warmer than normal for around 500 miles.

this is expected behavior..

and how quickly is immediately.. does it jump to 200 with the ignition on but car not running..

is the temp gauge at 200 after 5 seconds of running on a cold start.. (engine hast been started in 4+ hours)

this would be abnormal.. 200 after idling for 60 seconds wouldnt.

|UPDATED|8/19/2004 7:22:26 PM (AZT)|/UPDATED|

The temp gage is has a line at 200 and then the top is 280. Just below 280, aprox 260 is redline. I run just under redline in less than 5 minutes from a cold start. I hope this makes sense.

Did you replace the temputure sending unit? Most of the phantom overheating issues come from a replacement unit not calibrated to the original gauge. I had the same problem with my '76 L-48. I rebuilt the engine to all stock, except a Comp cam and bored cylinders 0.030.
My sending unit broke during the installation of the rebuilt motor, and the new one I got from Auto Zone didn't do the trick.
Check out this site for true original calibrated sending units and other electrial needs, it worked for me:

http://www.lectriclimited.com/

Hope this helps

Dave K

Thanks, this is exactly what I was thinking. I will check out this site.

I would not trust the OEM temperature gauge. There are so many variables and problems reported with them. Suggest you install a thermometer well in the opposite head and get a reading with a good quality electronic thermometer that is known to be accurate, then compare the readings.

True, I guess. I did double check mine with a I.R. thermometer, so I know that the gauge (on mine at least) is accurate.

If it is actually heating that quickly, you may want to go with a high flow t-stat. You could have a vapor build up behing the stat, and delay the opening. The extra holes in a high flow stat would cure this.

I suspect a bad sending unit.

Thanks everyone, I replace the temp sending switch today and I am now registering right at 200 solid.

Michael.