Oil in coolant reservior after short track use

Maybe UV leak dye for engine oil would help identify cracks in the block? Now that assumes it's on the outside - an internal crack wouldn't readily show unless you took the engine apart a bit. 93mph shouldn't have damaged it alone - the engine probably had issues running it hard exposed. You see people push even the risky motors like the 2L Theta II for 70-80+ without them falling apart at long term highway speeds.

@nick that is why you magnaflux the block ;-). First suspect is a bad head gasket, 2nd cracked head, 3rd cracked block :-)

How many miles were on that engine and what was the overall condition of that?

@oldturkey03 My guess is heat damage, especially on a street motor that was not built for track use. But at the same time it wasn't beaten on at 100mph+. If OP was running it at 120mph without having a built cooling system, then I'd probably say the speed did it.

Ill attempt a compression test & UV Dye this week if they're available, its at 130,000km on the engine. The A/C did stop working a week prior but the mechanic was full booked for a couple months and didn't stress that it would be a problem running for the time being.

@jacks2000 I do agree with your mechanic. There is never any rush to fix an AC based on mechanical reasons. Yes, its uncomfortable but it will not "hurt" your engine. UV dye will only work once you have your engine apart (or at least the cylinder head removed). For now, stick with a compression test and coolant pressure test.