found this video interesting.. 360 dyno testing.

Bewy said

It doesn't surprise me at all. If the engine is airflow & rpm limited by the cam, [ engine had a mild cam ] then installing heads that have bigger ports/higher airflow when the current heads already satisfy the airflow requirements of the engine, then the 'big' heads will add nothing...
Could actually hurt performance from big port volume reducing velocity.

Click to expand...

Yeah I was thinking about that too. The cam was pretty small at that stage. But to gain nothing was surprising. Sure a set of ported J heads can be effective, but man that short side on the exhaust port is just awful. The Eddie's in stock form are definitely better there.

I definitely wouldn't expect it to gain 50 hp or anything like that but for it to basically be a draw was surprising to me.