Re: is a 1600cc that much better.
I paid $700 for a complete 1600 8-valve longblock with starter and alternator. I got the 1.6 adapter kit from RR for $150. I decided to use a 1324cc head with the 1600 block for the increased compression (I've since heard the combustion chambers are the same size for both 1300/1600heads) and to use the mechanical fuel pump of the 1300 engine. The head was ported/polished and fitted with the larger 1600cc valves. The head I took off one of my parts Samurais so there was no cost in procuring it. The ISKY DP camshaft kit w/dual valve springs I got from the defunct VE for $250. The weber, intake, header came off the old 1300 engine. It all adds up to costing quite a bit ($1500 for the longblock completed) but I have no doubts that it would decisively outperform a 1300cc engine with the same mods but still be very reliable. (I've put on 30K in the past two years) Again, I bet it turns out at least 100hp but it still has excellent low end torque. Not as much as my 1600 with the torquer cam, but alot more than a 1300cc engine.
Also, the two Suzuki engines are nearly identical in design except for the fact that the 1600 has a longer stroke and therefore more cc's. The post '90 1600cc engines are all counterbalanced. Only the somewhat rare twincam 1300cc GTi engines were counterbalanced and 1300ccs destined for Samurais were never counterbalanced. Hence, the 1600cc engine is a smoother running engine too.
BTW, I have never had a problem getting a 1600 for just a few hundred more than a 1300 either. I guess on the west coast Hawk Suzuki hordes all of the 1600s and drives up the prices? Keep in mind, my 1600s are salvage models too. Not a rebuilt, so that's were I'm saving quite abit of money. I ensured that they were low mileage engines though. I took off the oil pan and head to verify this.
I've got nothing against the 1300cc engines but they just lack the grunt I need. However, I will admit I have several 1300cc engines laying around to swap-in if I ever need to swap out a dead 1600cc engine. I will probably never go back to a 1300 though. I have already got an eye on the 2.5 V-6 in my Dad's GV. ;-)