Have a chance to buy these merlin 320cc iron heads, grumpy special casting. Ho does these heads flow? Going on top of 9.7 to 1 compression, 509cid engine with gm zz502 roller cam. Are these any better than merc stock rec-ports. These are virgin set but would be bowl ported with good seats.

bring a sbc 1.50" exhaust valve w/ you,if you can run it thru the exhaust port,they can be made good.just have to watch out for breaking into the water passage by the short side radius.

Stan Weiss' - Cylinder Head Flow Data at 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software

They need work, as cast they are barely better than stock,Id buy the EQs over them fwiw