Displacement Increase Combinations
For those of you out there wondering how to make a larger displacement engine for cheap. here is some possibilities, first i'll show stroke and bore of the usual subaru engine sizes then ill explain the effects of mixing and matching.
2000cc/92mm/75- best bore/stroke ratio for big revs
2200cc/97mm/75- better than 2l low down and with aftermarket rods and pistons can rev like 2l
2500cc/99.5mm/79- heaps more torque lowdown, less revs to play with.
2145cc/92mm/79-2l bore with 2.5crank with 2mm shorter conrod- greater conrod angularity produces more leverage on crankshaft and creates much more low down torque than 2l but less topend due to rev limit similar to 2.5 engine,(budget autox engine)
2435cc/97mm/79- the best power combo here, almost same bore/stroke ratio as 2l engine, does not rev as freely as 2l due to 2.5 crank but revs more than 2.5 due to great bore/stroke ratio.
my ideal budget stroker: legacy 2.2 block with 2.5 crank, forged rods 2mm shorter than stock with forged pistons identical to stock wrx but 97mm instead of 92mm with version 6 STI heads and cams with .6mm version 6 STI 3ply stainless head gaskets
however i like the 7800rpm shiftpoint and 25psi boost of my EJ207 STI motor with only a set of forged rods and ARP bolts for safety.
some of you may notice some displacements familiar, many tuning houses do exactly this and charge you the earth. most of these parts are off the shelf. (not always subaru parts)
have someone measure your conrods and find a set of off the shelf ones identical which are 2mm shorter from bigend/wristpin centre to centre. these will work fine.