a few 400-406 SBC related threads and tips


The Grumpy Grease Monkey mechanical engineer.
Staff member

watch the videos, as they contain several tips you can use keep in mind that the 400 SBC , in O.E.M. form,
has a larger , block bore diam. and larger crank bearing diam, and in factory form it uses shorter than the common 5.7" connecting rods,
the larger bore allows the larger displacement for a given stroke, but the larger bore block required Siamese block walls, thus no coolant between the cylinders. as a general rule you can potentially gain about 1-1.3 hp and ft lbs of torque for each cubic inch of displacement you add over 327 cubic inches providing you match the components you use correctly thus a 383-406 sbc generally will have 40-60 more hp and ft lbs of torque than a typical 350 sbc built with similar parts.
the dart blocks are significantly stronger that the chevy block casting, the DART AFTERMARKET, CASTING is thicker in the most critical areas, and it's made from a stronger alloy casting.

AND A 750-850 CFM carb wakes up many 406 high compression SBC engines if they have at least 10.5:1 compression and a cam with at least 245 degrees duration at .050 lift cams
Last edited:

Last edited:

Last edited:
Ive had many people over the years rave about the results they get building a 400-406 SBC, and many of the same people would not consider building a 396-402 BBC , thats damn near always a bad decision in my opinion as the 396-402 BBC, if properly built with the correct matching components ,has a stronger factory or aftermarket block, a stronger rotating assembly and much better flowing heads, with bigger valves and a more stable valve train, (keep in mind MILDY reworked peanut port heads(about the worst BBC head )
( will significantly out flow the stock SBC vortec heads)
Last edited:

a few links worth reading through








btw, if you buy an engine you did not assemble and you have the oil pan off,
before you re-install the oil pan, on any reasonably newly rebuilt engine,
get out your torque wrench and verify the rod bolt torque is consistent,
its not all that rare for someone to forget to go back over the rod bolts torqueing them to a consistent value,
or for a bolt to loosen a bit if it was not properly torqued,
this may prevent future issues you could easily prevent in doing so.
just start tightening a couple and see if they are consistently torqued.
don,t get crazy just verify
many guys prefer to use a torque beam deflection torque wrench to check that.
you may want to look up the correct torque value for the rods used if you know.
but its likely close to 55 ft lbs, as you check, they should all be consistently torqued to a similar value

Last edited:
Id just point out that if max horsepower and torque is your goal, you might consider building a BIG BLOCK CHEVY ENGINE, as theres lots of advantages.