mmm, Ive heard of about 1400 cc.
Tis a mix of g13b and g13a bits , If you check the motors out some are 1324cc and some 1298cc, Im not sure they use the 1324 crank and an
60tho over on the pistons , could work it out but to lazy to figure out pie squared ect
Ive checked the possability of a 1600 crank in the1300 , but this is a
no go , just isn,t enough deck hieght on the 13 to make it work ,Piston skirt would have to be about an 1" 1/2 high to miss the throw on the 16 crank, motor would last about 5,000 ks
1500 sounds like a possability ,
The old type of stroking could work with this ,
You would need to find siutable con rods with a smaller big end diameter,
and a slightly shorter length, the scheme is to machine the crank journals off center towards the outer of its stroke ,down to the smaller journal size this affectivly increase the stroke, you need the shortnes in the rod to eleviate the piston running to high and creating to much compression , This is a simple way of explianing it its a lot more complicated then this sounds ,Cam timing ,balancing clearances ect ect ect . But ha I reckon there could be a market for ,a set up like this you think ?
Larry.
Stroked to 1.5 with obligatory cam/ head/ breathing work would be a good and essentially INVISIBLE power up 
