New 350 overheating during break-in

[Slonaker]

I just got my new 350 crate motor (Chevy universal 350 #10067353) installed and running. It started up easily, and ran pretty good considering that nothing had been adjusted yet. There were no odd smells or noises. Just the usual smell of paint cooking off of stuff.

In less than 5 minutes, the temperature, as indicated, was at 210. I shut it down. I messed with the timing (several times), tried it with and without the advanced hooked up, and ran it with and without a thermostat. None of it made a diference. It always indicated it was running really hot even though t was about 50 degrees outside.

The old 305 was okay with this radiator, fan, water pump, etc. They are all relatively new except for the fan clutch. It has new belts and hoses.

The odd thing is that it did not feel hot or smell hot. I could grab and hold the upper radiator hose even when it said it was overheating.

I installed a mechanical gauge I had laying around in the water neck, and it didn't even move the needle. I also dunked the bulb in a pot of boiling water, and it moved very slowly upt to about 150 degrees and sat there. I don't trust it now, so that was no help. I may end up buying another one tonight to see what happens.

I'm wondering if it is really overheating, or if I have a sending unit that is incompatible with my gauge. The hole in the head for the sending unit is a different size fro the one for my 305.

Sallee Chevrolet, on their website,says "Temperature Sender-Vehicles from 1979 and up will require a temperature sending adapter P/N 00444034 which Sallee Chevrolet can supply you with if needed. The sender is located on the driver side of the engine and has a green wire going to it." I went to my local dealer, but the lady at the parts counter said it was a bad part number. It apparently is since it does not show up on the websites for any of the Chevy dealers, including Sallee Chevrolet where I got it from.

I ended up just going to a regular auto parts store and buying a sending unit from a 78 Chevy pickup. Could it be that it is not compatible with my gauge? Has anyone else come across this problem? Did you use a different sender, or an adapter?

Can anyone think of anything else that might be causing it to overheat?

Slonaker