mjanczura Dump the dope to start. Lets start with simple things
Radiator cap has a pressure rating, said on top from 12 to 17 psi. At this point to releases pressure to over fill tank or on the ground. Griffen radiators will take 25-32 psi. No way this happened.
Does you car have side pipes and the motor have a little lope at idle? if yes, again another BS story of hearing the radiator pop. You should have blow a radiator hose before a core.
Sounds like you dope blew an head gasket and not wanting to eat the repair point the blame at a failure of a part.
Start with a home test. Check the
oil level and color of it. Should be clear and golden color. If at full level Start the motor and let it run at idle. If the motor is overfilled and the
oil is cloudy, DON'T run the motor, you could have coolant or water in the motor. This will wipe out the bearings. This means blow gasket. Stop here and have car towed to another garage and have checked. Sue the dope later for screwing up your car, keep all bills. Make sure the level is full, Put a drain pan under the car. If you have a coolant pressure tester this would be big. Let the motor get to operating temp and check for high pressure or bubbles coming into the top of the radiator. GUESSING he blew a head gasket if the car had no problems before the exhaust gasket was replaced. Guessing, you need to replace gaskets and that the damage is little, couple of
oil changes "should clean out the rest of the water/coolant" Don't beat on the car. Check your oil pressures, they should be within 5 psi before you had the repair if they are more, than a motor rebuild would be the right way to go. Good luck. Rick Ps You live if CA, find some local cobra guys and see where they go for repairs. Pss you didn't say what kind of motor you are running but my all aluminum motor heats up in about 2 minutes to 198F and then drops about 30 degrees once the thermostat is open and balances out to 180-185f when racing. At the end my temps are about 195-198f. Rick