I'm telling on myself here, and it may bite me in the butt, but i built a 481" a couple weeks ago for a person in Ms. He brought me a set of BB2 Extra heads that the person who did the work on them used recessed retainers and super 7 locks. I dislike these retainers because it's necessary to use a longer push rod for the rocker to clear the retainer. I put it together and had trouble getting a good geomertry on the exh valve useing available push rods from Comp cams. The ent. came out good, but i'm still concerned about the exh geomertry, i had .120 int clearance and .190 exh. clearance with the pistons. The whole engine was a nitemare, it had a cross drilled chevy steel crank, the weakest that GM ever made, it had Speed Pro dome pistons, probably 800 grams and the block had 3 Helicoils in it. But WoW :shock: it had Lunati Promod rods, i just hope it lives. I know a person who spent tons of money on a 406" sm/blk (2 times) and neither lived more than a few passes. He then put togother a junk yard 406 and lasted 2 seasons and ran better than either one of the good motors
go figure.
Zip.