Help. Just bought 89 Camry for son. First car. Faulty Radiator cap blow engine. Engine and head redone by qualified mechanic but won't start. Plenty of spark, compression etc. Good Mechanic pulling hair out. Any suggestions?

Spark + Fuel + Compression, and all at the right times.

Check for spark first, then check fuel is getting to the injectors, then compression.

Make sure the distributor, or cap isn't 180* off.

maybe the air, this engine is quite rare, all computer control. if the computer go wrong, engine will not start, for V6 as I know

Does the engine turn over? It may be your Air Flow Meter, located between the air filter and throttle body.