Hi all.
I recently had to rebuild my '76 350 due to a faulty cam. When I reinstalled the engine, I noticed that the temp gauge reads between 210-230 (sometimes higher) when prior to the rebuild with a 180 degree thermostat, the temp sat around 180 to 190. The kicker is that the original temp sending unit broke just prior to the reinstall, so the new readings is with a replacement sending unit from Corvette America with a new 160 degree thermostat. The engine wasn't built up much during the rebuild, with the exception of 0.030 flat top pistons and a 270H Comp Cam. Everything else is stock.
I was wondering if I could have an air lock in the engine due to the fresh rebuild, or is the temperature gauge just wrong.

Thanks in advance

Try to find someone with an infrared temp gauge. Have them check a few different places on the engine and the hoses to see what the temp actually is. Chances are the sender or the gauge is not reading correctly.

Dave,

Did you let the car run with the radiator cap off to purge the air from the cooling system???


Roy

Yes. I did leave the cap off in an attempt to get all the air out of the system. However, I didn't get a chance to do this until a couple of days after. When we first fired the engine, we had to do a cam break in as soon as the engine started (2000RPM for 20Min). We didn't get a chance to check other systems at that point. After messing with the system some more, I think I got all the air out of the system.
I did get a chance to borrow an IR Temperature gauge and tested the intake manifold. The readings came back about 160-180, and the temp gauge in the car was on 200. I guess it's safe to say that the gauge in the car is off.

Thanks for all the advice.

Dave K.

I had the same problem with my 72. I replaced my sending unit with one from Mid-Amer. and it was not accurate. I bought one from Lectric Limited, Inc. (www.lectriclimited.com) for 19.95 that was made for the older corvettes. It is within four degrees of the temp gun. You might give them a try.

Thanks. I may try that new temp sender.

I replaced my temp sender a couple of years ago with a $12.00 unit from (I believe) Paragon. It always read high with a 180 degree thermostst. It showed the thermostst opening at the hash mark between the 200 and 225 degree marks. Sometimes it would creep all the way to the red line!

I clamped an AC type thermometer to the radiator hose right next to the thermostst housing (cheaper than a laser thermometer) and found that the guage was reading 32 degrees high!

I believe I read (maybe in Dr. Rebuild's catalog) that even in the ZIP catalog there is a note that aftermarket temp senders can be off by as much as 30 degrees!

After several posts on numerous forums, I received lots of advice. One in particular was to avoid the common recommendation of inserting a resistor in the circuit.

The best recommendation was to get a Wells TU5 ('69 350 engine) temperature sender. I found it at AutoZone for $4.00. It now shows the thermostst opening at the hash mark befor the 200 degree mark and it remains ther constantly without drifting.

"The best recommendation was to get a Wells TU5 ('69 350 engine) temperature sender. I found it at AutoZone for $4.00. It now shows the thermostst opening at the hash mark befor the 200 degree mark and it remains ther constantly without drifting

Absolutely. Unless you can get a NOS or the LectricUnlimited version - these work.