The sodium transfers the heat out of the valve on the exhaust and puts it into the guide. Airplanes have been using them since the 30's


1941 Taylorcraft
1968 Charger
1994 Wrangler
1998 Wrangler
2008 Kia Rio
2017 Jetta

I didn't do 4 years and 9 months of Graduate School to be called Mister!