In order to fit increase the displacement of a water boxer, the crankshaft stroke and/or piston diameter has to be increased. Here is how the stoke/bore (in mm) shakes out for the engines and engine kits we sell, as compared to the original dimensions:
Original VW 1900cc: 69.0 x 94
Original VW 2100cc: 76.0 x 94
GoWesty 2200cc: 76.0 x 96
GoWesty 2300cc: 79.5 x 96
GoWesty 2450cc: 84.5 x 96
GoWesty 2700cc: 84.5 x 100.75
As you can see, all GoWesty engines and kits employ a crankshaft with a longer stroke—except the 2200, which uses the standard 2100 crankshaft. But, even in the case of building a 2200 out of a 1900, the engine block needs to be modified because the 1900 and 2100 engine blocks are not exactly the same on the inside. In order to fit this larger stroke, the engine block needs to be hand-ground in key places where the crankshaft or connecting rod interfere with that part of the engine block. Also, as shown above, all of our engines and engine kits employ a larger diameter piston. At bottom dead center (BDC), the larger diameter piston will come very close, and even touch the engine block. So, all the engines we build (and kits we sell) require some hand modifications for the pistons to clear, as well.
The actual amount of material that has to be removed is very little, maybe 2-4mm deep, and 10-20mm wide. The exact depth and exact location varies from one engine block to the other. That is because the engine blocks are cast aluminum, and as such differ a little from part to part. It is simply not a matter of “take 2mm off this spot, and 1mm off that spot.” And even if it were, you are doing this by hand—so you can’t really tell when you have taken off 1, 2, 3 or too many millimeters—it takes some serious practice. The process is to literally assemble one half of the engine with a rotating crank/piston assembly to see where the interference is, mark the spot, take it apart, hand grind some metal, put it back together, and repeat. Then, do the same to the other half of the block. Then, when you are all done with the hand grinding, you have to take everything apart and clean everything. And you wonder why GoWesty engines are so expensive…?
Basically, you need to be an experienced mechanic to A) build even a bone-stock waterboxer engine, and B) be a highly talented and brave individual to build one that requires modification involving taking a hand grinder to an engine block.
Definitely not for the faint of heart—or anybody with unsteady hands!