Hey guys
I recently heard about enlarging 6g75 to 4.2 or 4.6 which is it? I would like any info, has anyone actually done it? What sorta power torque gains are there? How much does it cost to do? Does anyone have one for sale?

4.2 is a 4.5mm bore increase - minimum cost is the boring plus the custom pistons. At least one has been definitely built and run in a Magna. 4.6 requires $ignificant modification of crankshaft and custom conrods on top of 4.2 changes, not sure whether this has been completed. No public output info I'm aware of here; there may be some in the US (Eclipse & Galant).

Search 'bored' and 'stroked'

Bored 4.2 been done with rough results in that thread. Stroked out to 4.6 not done due to costs getting striker cranks being $ thousands.

Awesome thanks, I searched those words but nothing came up related to it. If you could link me to some info would be appreciated. How much do custom pistons cost, or can you use pistons from another engine?

@ seriousmagnaman, I've sent you a PM.
I doubt you'd see any change out of 10 large to do this along with cams & headwork (assuming you've got a 6g75 already).
For the sort of money involved, you'd get much better results keeping the 6G75 standard bore/stroke & doing a small turbo air to air intercooled install. You can run upto 6 to 7 psi on stock internals & the transmission should be able to cope depending on it's condition - trans cooler & wave spring washer replacement mandatory (if your TL isn't one of the last ones before the TW).