X1 ............... Agreed. Before tearing down all the heads and other components it would be would testing for exhaust gases in the coolant system as it's likely there may be other issues and this will help eliminate them. Be sure to warm up the engine first though to working temperature and be very careful when you remove the coolant cap.

 

The coolant system is in perfect working order. The trouble is it is being pressurized quickly and forcing the coolant to puke from the reservoir. It will idle for 30-45 minutes at 195. Drive it for 2 minutes, and it quickly approaches 230 and pukes all the coolant out. I believe head gaskets are wishful think at this point. It very well may be a cracked block.

 

You said yesterday you were going to try a new coolant reservoir cap. Do that before you do anything more drastic.

 

I will. Unfortunately, I believe it's just wishful thinking. Thanks.

 

Also, with the engine cold, if I take the cap off the reservoir and start the car coolant begins to build pressure and overflow within a minute. I believe this to be combustion gases.

 

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Thermostats can, and do, sometimes go bad in a heartbeat, sticking open or closed. I have seen that happen many times in family, over past 50+ years. That is why, a long time ago, I installed an inline thermostat on my Rover, using a cheap Chevrolet 180 deg. thermostat, available anywhere, any small town America. As we all know, heat is a huge enemy of all aluminum block engines, especially the Rover V8, due to extremely thin aluminum walls between the water jacket and the cylinder liners. That thin wall aluminum, under excess heat, is likely to crack, usually just beneath the bottom of one or more of the threaded head bolts, between the water jacket and the liner, which otten leads to the liner(s) loosening up, and slipping up/down, in sequence with pistons. Thus, you have every reason to be "a bit nervous." After you determine, for certain, the extent of any possible damage, please let us know.