i think one of the main problems with these new bigger engines in our bays in there's not enough room for the air to circulate around, i've got a ca20e in mine and without the elec cooling fans it overheats so quickly. my mates also got a mk1 esky and it has an sr20det with 300hp and he's got fairly serious overheating issues, it only ever really sees the track though.

edit: and never ever go with a ca20e, mine came with it already installed and i got it cheap but yeah it's a crap motor and i sometimes wish i either got a stock one or shelled out some more for a decent engine.