Help! 1965 corvette temp

[MCCONE]

I am having a heck of a time with this one.
396 big block - The temp gauge starts out normal and then slowly rises and sets at 240 before the car is even warm. Here is what I have done.
New Radiator, new clutch fan, new thermostat 180, new temp/water gauge, 3 difeerent temp sending units(No tape or dope on the treads).
Checked the temp wire it reads 4 Ohms.

Any Ideas or recommendations?

Thanks

 

[crowvet]

Bad ground strap somewhere from body to frame. Try running a ground wire from the battery to the instrument cluster and see what happens

 

[MCCONE]

Thank You...
Appears there might have been a two fold problem.
Bad wire and connector to the temp sending unit.
Had it out for a while last night. All seems to be working properly.

 

[crowvet]

Glad your COOL again.