Hello All,
I had my 408 short block built and my 317 heads cleaned up. The machine shop put the little disk on the freeze plugs that show if the heads get hot. Well this build is going in my Chevelle. I got everything wired up and I thought I had tuned in the fans to command on. I started the car and had 80ish psi on 5w-30 break in oil. I let the car run for a minute to check all fluids and realized I needed to tune for the cam. So I tuned the setting and ran the motor again. Each time running very short. Once the car idled good I let it idle and walked the engine to ensure the trans fluid was good, coolant was good etc, well the motor ran for maybe 10 mins total and started to warm up. Mind you my garage is 60ish degrees. I temp gun checked the heads and I saw 235. So I shut the car down. It was still idling well. And I saw that the middle of that device on the freeze plug had slightly melted out. Not empty but it was like a water droplet coming out the middle. I let the car cool off and restarted it with the fans getting full power. The engine cooled off and everything seemed fine. Should I worry? Hell I bet the motor doesnt have 20 mins of run time.

 

Those tabs melt around 260 f, depends how long it was run at those temps. Its so you can go back after the builder if the engine fails. I personally wouldn't be too concerned ay this point.

 

It wasnt ran long at all. It was still running good. Doesnt the computer shut things down to protect the engine? The car was idling fine. The metal in the middle didnt even fall out it more sagged out. So it barely liguified then re solidified very quickly.

 

Did you bleed out air from the top of the heads (at steam crossover tube)...?