Got a 406 in mine, stock crank, 5.7 rods, 10:1, 180cc pro-actions, small cam, 750 vac sec, makes 400hp and 450ft-lbs... it's a nice tire shedder... Build it... but buy a stud kit or put splayed mains on it...
the 509 block is the circle track cheeter block 2 soft plugs. the casting in the main web on all 400's that i've seen is thin . splayed cap's get the outter bolts into a more meaty area.watch out for cam to rod interferance . KB has dished pistons for your combo and will be fine , but gap the rings to there spec !!! I run a high volume oil pump and open up the main galley lines to 1/2'' and the main bearing feeds to 5/16'' you may have to open up the groves around the cam bearings some are on the small side. Most bottom end failure's on 400's i've seen were oil related not crank or main cap . Cooling one I only drill the outer holes in the heads and run a water pump, pully and restictor combo to get about 30 psi. in the block .The crank snout failures I've seen on blown SBC's were keyway so now i broach a second 1/8'' key into the damper .
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