Fred,
i spent a lot of money on building my 406. it was made to rev and hold more power than it is tuned for at this time. i am making 606 hp and 588 ft/lbs on 90 oct pump gas without spraying it. i can run a 200hp shot of nitrous safely and a 300 shot will be pushing the limits of the block. i am not going to kid you, i spent (without the learning curves) an easy $11,000 on getting it running. there is a lot of bad press floating around 400sb chevs. the old blocks ('72 and '73 i think) did not have the steam holes drilled to cool the siamesed cylinders. IT IS CRITICAL to have the steam holes in the heads and cylinders. a siamesed block is actually stronger than a 350 block, according to several books i have read. if you go this route, go with a two bolt main and put splayed caps on, easy insurence. a stock four bolt block's outside main bolts go through the "fissures" in the main webbing. a splayed set up will go parallel to the fissures and not ruin the integritty. i am running the stock radiator and fan with an edelbrock high flow water pump and 180 thermostat. i yarded the a/c, living in alaska go figure, and the hottest mine got was 190-195 after a grueling burnout/speed run for a couple of miles of wfo, outside air temp was 85.
406's are bad to the bone. they couple light weight with big displacement, a win/win in anyone's book. they really are not that much more to build than a 383, but can offer more. there is no replacement for displacement!! i have a fairly large well of info on building a 406 or 434 sb. there are things i would do differently with the gift of hindsight. you still need to figure out how much cash you are willing to throw at this project. hp takes $$$, but the numbers you want are not going to cost your first borne. the first itteration of my motor was 10.3:1 comp, 2.08-1.60 valves, dual plane intake and a 234/246@.050 cam with .498 lift. it made 440 hp and 520 ft/lbs. it made 418 ft/lbs around 2000 rpm but fell on its face after 5400 rpm. it had 18 inches of vac at idle. it was a killer build for a 4x4 or car equipped with a 700r4. give me a few dollar figures and i will give you a few options to ponder. MAKE SURE YOUR MOTOR GUY KNOWS HOW TO BUILD A 400 RIGHT. it will be worth talking to other people that have a 400 built by your guy. there are no second chances when it comes to machining on a 400sb block. it is easy to screw up and cover the mistake, but time will make that mistake known loudly. i will try and email (forward) a partial dyno print of my motor.
