400-425 hp is generally OK in a carefully inspected OEM sbc,thats been carefully machined, engines built,on a decent non-core shift block,
yes its a bit over what the block was designed for,
but hundreds of thousands if not millions of guys build SBC engines,
in that power range that last for decades,
its when you push to over about 450 hp your just pushing reasonable limits.
keep in mind your engine may be making 430-hp at 6300 rpm,
but keep in mind, realistically,
it will spend 90% or more of its actual time making power at much lower rpm and stress levels
if it made 430 hp all the time like if you were running a circle track engine,
it would never last nearly as long as it can in street performance use,
where you may spend 40 seconds every few days at most embarrassing some kids turbo mazda.
one reason Im a big fan of the BBC, is a properly machined 396-496 BBC can use the O.E.M. block and crank and in many cases even connecting rods if the correct rod bolts are used,
to make 450 hp-550 hp and the O.E.M. block and carefully selected and carefully prepped O.E.M. components works just fine.
450 hp-550 hp, in a reasonably light weight car,
like a camaro,nova or cobra kit car, t-bucket, or Vega,
with the correctly set up suspension, tires and gearing can be a great deal of fun.
obviously you have options
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a set of those dart heads is almost $1780
youll spend a bit more (about $400 more)on profiler heads but they would easily boost power at least 20-30 hp
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Air Flow Research's 195cc SBC Race Cylinder Heads are the preferred choice for a more aggressive street or street/strip build. 195cc SBC Race Cylinder Heads feature 100% CNC ported intake, exhaust & chambers, A356 aluminum castings and high quality components throughout. Recommended for...
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as a general rule, on a SBC performance engine build ,
try to select a cylinder head that reaches or exceeds 250 cfm at .500 lift and ideally 280 cfm PLUS at max lift PLUS
or you could get similar performance to the dart heads for several hundred dollars less
Air Flow Research's 195cc SBC Enforcer Cylinder Heads feature AFR's Permanent Mold “As-Cast” Technology surfaces on the intake runners, exhaust runners and combustion chambers that allows for extremely accurate and repeatable port location/performance. This budget-friendly cylinder head is...
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only loosely related but fun video