I guess I will have to ask you how you define DECENT DRIVER,STREETABLE in the same queston as MAX HORSEPOWER...my 250 is .060 over bore with 307 v/8 flattop pistons,full balance,.060 off the head,.194 350 v/8 intake valves and .160 exh. valves. The valves pockets have been cleaned up with a lot more work done on the exh. side the cam is a old Clay Smith with .519 lift with .258 duration on the int.side and .266 on the exh. side. The lifters are Crane Hi-Rev left over from years ago, good to 7000 rpm.s I use some double wound valve springs removed from a set of Mondello heads I use to use on a "c" Dragster in 1978. They have 94 lbs. on the seats which work fine for me as my motor starts giving up(flowing) at about 5900 rpms.I call this motor DECENT DRIVER because It has a good idle,starts good,runs on reg. unleaded,runs cool,and gets 20 mpg with a 3.36 gear in a 1950 Chevy.I have seen 4000 rpms in hi-gear...do the math.....to old to be a prima-donna, but maybe a old coot..SCRAP
