I have a 396 bb and for the last 2 days I noticed that my after market electric temp guage is off by about 40 deg. It's been perfect for 5 yrs....Would it be a good idea to start with changing the gauge first?

Check your senser that goes into the head. Should be a brass senser on the head or block that gives the signal to the gauge as to the temp. They do go bad and will give wacky readings. Good Luck

jersey,
What do you mean when you say it is off by 40 degrees ? Is it reading 40 deg hotter or cooler than normal ? There might not be anything wrong with the gauge, the engine might actually be running at that temperature.

Thanks for the replys. I should have said that the 40 degrees off was lower than it normally is. It totally stopped working now, so I will replace the temp sending unit and gauge. I just found out that with an after market unit they are all one piece.