230 Flathead w/ stuck thermostat ?

[farboat]

I have a 1942 WC-52 with a 230 flathead 1300 miles since rebuild. Just recently (2 times) I have noticed a maxed out temp guage approx 5 min after startup. The temp guage goes to 200+ degrees for maybe 1 second and then quickly drops to 160 degrees, which is normal temp. I'm thinking the thermostat is sticking. Is it possible to drill some small holes in the thermostat to flow some coolant to prevent this, or should I change out the thermostat ?
Thanks for any help
Greg

[Rodney]

Test thermostat

Test It. Take your thermostat out and test it with a thermometer and a pot of water on your kitchen stove. If it does not function properly (open at 160), replace it.

[Gordon Maney]

Another thing you can do for diagnostic purposes is take an old thermostat and remove the valve from it, leaving only the large, washer-like part. Put that back in the housing. This will approximate an open thermostat.

Warning — Do not run the engine with no thermostat, as this will allow excessive flow rate and can cause overheating.

I am not suggesting a modified thermostat as a permanent solution, but if it changes your symptom from that which you describe, then you can know it is your thermostat.

[farboat]

I tested the therm in a pot of water and it opens perfectly right at 160, so it must be an intermittent problem so I'll be changing it out to be sure.
Thanks for the help guys.
Greg