I built a 1/2 cut case, VW engine a few years ago. It weighed 89 lbs. A 4 cylinder VW 1600-1835 cc, short block engine will weigh 116 lbs. My 1835 cc, 60 HP VW engine firewall forward weight is 141 lbs, (no electrics).
I was told by a friend of mine that has built several 1/2 cut case VW engine and several full case 1/2 VW engines and he said that you saved about 7 pounds by cutting the case. Don't know how accurate . You are really just cutting about 3.5" off the case and the real weight saving is the cut crank and cam.
BTW-- I saw a 1/2 VW at OSH years ago, that used one side of the engine. Didn't see it run.
First bike I rode was a Triumph and then a BSA. Never could decide which one I like the best. DanWhile reading the notes above I realized that in my youth I rode many an older Brit bike (BSA, Triumph etc.) on and off track, and they had 2 cyls on top (= side). Called in-line twins and all ran pretty smoothly. Difference is that they had 360 degree cranks. I.E both pistons rode up-down together with a bang every rev, one side then the other 360 deg later. Of course they also had pretty hefty counterweights on the crank but with careful prep you could run the Triumph up to 6K regularly. Many road racers used these in the 50's and 60's then Yamaha happened!!
First bike I rode was a Triumph and then a BSA. Never could decide which one I like the best. Dan
The full case 1/2 VWs, also cut the crank, and cam in half.There is significant weight difference between 1/2 case and 4 cylinder engine. If that mod done properly, like cutting case and crank, it will save lot of weight....saving list include: approx 1/3 case, 2 cylinder, approx 1/2 crank, one head, two piston, two rod.....I read somewhere that there is some "conversion" that use full case and crank, but that will be odd and inefficient way to do it, only small benefit for weight and power level only 1/2 of original.
The VW engine/air compressor was advertized in the U.S. in the 1970's in the VW auto magazines, but I never saw one.In this country there was a common range of air compressors found in hire shops for road breaking jack-hammers that used a VW engine with two cylinders on one side running as an engine and the other side cylinder pair used as the air compressor. The compressor side used a special cylinder head with reed valves.
It was a pretty neat arrangement and I recall they ran smoothly with an even firing interval. I have no idea if they were fitted with a special camshaft to enable this configuration.