J-head to eddie swap?

I did the same thing. Loved it. Combo was a tad different.
Went from 2.02 J's to OOTB Edel heads. And a purple cam.
The smaller chamber is more so for upping the compresion due to the heat loss of aluminum as well as getting a nnice quench area with the reduced chamber size. The quenched area is were the power comes from as well as better ports.
At the time I was running varrious purple cams.

I liken the gain as very much like going from stock iron heads to ported heads. Not a full port job, but a well preped deal.