the fact that it has 2 more cylinders helps just a little too… rbs also have cast iron blocks the can typically handle more power than an aluminum block
why the 400 whp goal though? is it just a # you like? sure, my drift car makes 450 but I only run it at 340-350ish whp because that is more than enough for me to smoke my giant 275s in 4th gear.
who really cares what his reasoning for his 400 hp goal is, we know it wont happen anyways, even if you gave him a specific parts list for sr or rb or ls1 or god damn b20 vtec lol,
but seriously he just wants to know the cheapest way to 400 hp - whats wrong with just sayin a stock motor with a set of cams, arp head studs, gt2871r, injectors and a good tune ? im sure he could stretch 400 hp that way, but it may not be super reliable, yeah sure a few more parts will keep him reliable, but let him do his research, like dave said for drifting, 350 hp is plenty when your car is light like s13,
maybe he will tune his car to 350 wheel, and take it for a drive and say ok… since im used to under 200 hp in my entire life… maybe i should get used to this for a year and then see if i need 400 hp… look what guys like vlad and pat are doing with under that power ??
anyways, my opinion i just thought we should at least answer his question instead of just telling him he doesnt need it,
IMO the most reliable way to get 400hp is a LS1
racing one 2 years now…no issues…just turn the key…change the oil…and off you go…runs 12’s in the 1/4 and is no fuss
the torque makes it wasy to drive vs turbo cars…and there is tons of upgradeability
plus easy to get local parts
initial cost is higher than a RB or SR…however long term its the better way speed wise anyway