Dave, you're on the right track however trying to compare a 6 cylinder Porsche engine with a 4 cylinder VW engine doesn't work. First off, the Porsche engine is actually 3,164 cc's with the combination stated. If you could find a 74.4 x 95 VW engine it would only produce 2,109 cc's for a difference of 1,055 cc's.
The added 2 cylinders on the Porsche engine coupled with overhead cams, better head design and better fuel induction all add up to more power.
But, I've built several engines with a 74mm crank with various size of pistons and for a street car, they work great.
The 356/912 engine was rated at 1,600 cc's as was the VW.
Porsche and VW were generous in their published engine displacement as the Porsche engine only had 1,582 cc's with a bore of 82.5 cc's and a stroke of 74 cc's.
The stock 1,600 cc VW engine produced 3 more cc's at 1,585 cc's.
It had a bore of 85.5mm and a stroke of 69mm's
But remember this, regardless of which gasoline engine you're talking about, all of them have the same amount of torque and horsepower at 5,252 RPM's.
The combination of better heads, better intake/exhaust, different cam profile and twin (2) barrel carbs made it a much stronger running engine than the VW's version. In addition, the 356/912 engine was a 3 piece design as opposed the VW's 2 piece engine case.
VW's biggest downfall when dealing with aftermarket hot rod components are their heads. That's why so many people were making aftermarket cylinderheads with large intake and exhaust ports, larger valves and with re-designed intake and exhaust runners.
Anyone can assemble a VW engine but getting it to produce torque/HP is another story.
But remember this, every gasoline engine produces the same torque and horsepower numbers at 5,252 RPM's.
