i have run both stock Source heads , home clean up , and now CNC Source heads .
On a 440 ci RB +0.055 bore . Solid flat tappet cam 258@050 - 540 gross lift (0.020 lash) , 10.75ish:1 comp
Best ever pass on old heads was a 10.994@120.66 . Only ever ran 1 10 second pass mostly ran 10.10/18 range
With the CNC best pass is in my signature - 10.88's . In fact at a street meet last night with no track prep I ran a 10.893 with a PB on the sixty of 1.497.
Currently has a Eddy Victor manifold , gasket matched only , with Prosystems HP1000 carb .Mostly ran a M1 single plane and sometimes a BG 825 on older Source heads - BUT I had also run the Victor and HP1000 for minimal gains . On the chassis dyno there was about 30RWHP gain . This was all in flow - as the gain was in the swap from the 825 to the HP1000 . Timing needs did not change and only needed I think 1 more jet size in the rear .
I know I need more cam but I am not legal for sub 11's and I do have a another block that is calling out for a 4.25 crank kit
I am very happy with the result . are they a race head NO are they a good performance head YES with the proper prep . The straight plug is really nice too .

Tex