Ive done quite a few engines. Mainly flowing the sleeve. The cranks were quite good so never touched the crank.
The only timing changes Ive done was raising the exhaust port by.5 or 1 mm. This took away some bottom end and better top end.

On My SH28 6P I raised the exhaust port and flowed the engine. This beast was just way too powerfull. It revved better but snapped the rod. This mill cannot take repeated high rpm, top heavy.