This is more out of general interest then actually planning in doing it myself. I was wondering if any one had ever bored out or done research on boring a 3 litre block to the 3.5 dimensions (2mm larger or what ever it is) and then also fitting a 3.5 crank and 3.5 computer etc etc, basically turning a 6g72 into a 6g74. Is everything else on the 72's and 74's the same besides ECU, crank and bore? ie: are cams, injectors etc all the same on both? I was thinking along the lines of if you had a 72 that needed a rebuild, ie: new rings in particular, then how possible would it be to bore it out and throw a 74 crank in there along with ECU, is it that simple?

nah bud the block is longer in the 3.5s. your ECU is minorly different (maps and ect) and if you were to do it im SURE you would end up with WACK compression or valve meets piston problems

http://www.aussiemagna.com/forums/showthread.php?t=4705All your answers are here.

Mitsuman:
But any cubic increase is worth torque which is always good.

:cry:

As they all said. Same 6G family, different block 72 v 74. There's not much difference but a difference none the same. I'd just drop the 3.5 in as opposed to modifying the 3.0. I'm sure cost wise it's not worth it.

mitsubishi would not have designed and cast a new taller block (6G74) if they could have got away with just stroking / boring the 3.0 (6G72). boring out and replacing 3.0 slugs with 3.5 ones should be easy enough, but i doubt there is enough travel at the end of the cylinders for them to work with the 3.5 crank. maybe cylinder sleeves could do the trick tho.
at the end of the day it would be far simpler to just put in the 6G74

would it be possible to use the 3L ecu with the 3.5L? i imagine the 3L has a higher rev limiter :D and is designed to have a bit more torque from ign and fueling (cos the 3.5L has it naturaly)

mitsubishi would not have designed and cast a new taller block (6G74) if they could have got away with just stroking / boring the 3.0 (6G72).
Good point, maybe it's just the ports that are in a different location? Dunno.