I picked up my 29 a couple months ago. It has a Chev 350. When I first start the car and get it on the road the temp gauge will hit about 230 quick. Then after maybe a minute of hitting 230 it will go from 230 down it 180 in less than 30 seconds. It will stay at 180ish the remainder of the drive. The old owner said it started doing that after he put on the aluminum heads. I noticed the temp sender is located on the side of the head. I usually install them in the intake manifold. Any thoughts? Also, the electric fan is wired to always be on. So its not the fan turning on and cooling it down. If it was a stuck thermostat, I would think it would stick more than just the first 5 min of drive.