Installed another new thermostat in the Willys.
Some stats come with a solid disc and some have a tiny vent hole with a loose rivet in it. The L-head motor, by design, needs the vented thermostat. Did a little more research with some of the old school guys!
There is no overflow on the radiator for the L-head engines. If you fill the radiator, it will dump the excess coolant on the pavement, as it was designed to have expansion space in the top of the radiator. The thermostat housing is above the head and even with the expansion space at the top of the radiator. If no coolant touches the stat, it doesn't open right away when it gets up to temp, causing a heat spike up to 210 degrees or so until the coolant expands enough to touch the stat. The tiny vent hole in my new stat allows some of the coolant / air to pass and causes the thermostat to open close to 180 degrees, as it should. 210 is not super hot for a modern engine and cooling system, but the L-head was designed to run in the 180 degree range with 100% ethylene glycol coolant. If you run H2O or a mix, you need to use a 160-165 degree thermostat.
I'm getting real good at cutting gaskets with an exacto knife!
(Jenn, you need to add this to your list of things to check with your CJ2A. Don't know if your temp gauge works, but it wouldn't hurt to be sure you have the correct stat!)
