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Trying to build up the 100% all-purpose engine is hard. If you wish to run 200kmiles, you want something, that even Porsche never did (ok, maybe 80year old grandpa drove only 55mph straight for 30 years, but even then...)! My tips for such an engine would be....
Some words to the cam. The profile, that a German GB 2,0l 100HP 914 engine has, is a 272° cam (or US ~252°) with 106° spread, 10,9mm Valve lift (8,3mm cam lift), 2,8mm lift at TDC and a wide powerband for an original engine, that lets you rev up to 6000rpm with a good overhauled valve train. It's a good cam, that can run very well with the d-jetronic.
I would blueprint all the internals, resurface the flywheel, balance flaywheel together with pressure plate crank and gears and keys. Trick item here for me would be a very reliable and powerful Fichtel & Sachs pressure plate with an aluminum race ring, as it is nearly 2kg lighter and is totally stock in optics. You don't have to machine your flywheel. Another trick item would be a set of 57gram Witzemann lifters, as they are in stock size, look like a Type 4, but are pretty light. Together with slightly tapered pushrods, equal weight intake and exhaust rockers on straight mounted shafts (without wobby shims), together with lightened original valves ot 7mm stem valves from Schrick, a good and reliable conversion. Machining the c/chamber to a better form is hard, but possible. More sense would make 100% exact volumes. Most important for me is a totally straight case, where the main bore sits super straight and the deck heights are totally the same. Only a good machine shop can do that in real high quality. Then you can be absolutely sure to have the same c/r no all 4 cylinders and having correctly angled rods in your engine.
At least I would prefer the combination with Type 1 pistons in 94mm bore (B-type for 82mm lift) as they are approx. 120g lighter than the 914 units, are "press"-forged and dissipate the heat pretty fast.
Are there restrictions on the seat machining? First, start with new seats, bigger outside diameter. The originals tend to fall out, as they were pressed in with not enough oversize by factory!
There's a lot of power in machining the seats more "racey", e.g. radius the angles to the port and to the chamber, seat width only as large as needed etc.! Exhaust port matching to the exchangers, machining the exchangers to a straight and oval surface, maybe fitting an old 911 muffler to your 914, as the mufflers are interchangeable from the old models.
Running a small (Schadek) drysump pump is a must, as the hp and reliablility gain is worth the lost power of getting the larger gears turned. Even the cooling with the original, stock cooler is better then (having 8-12 Liter in your sump system helps :-) and maybe some harder or underlayed pressure-springs are the way to receive a more constant oil pressure under all conditions.
At least, measuring, measuring, measuring... is the most important thing you can do to obtain a 100% engine.
If I would give a quote... a German GB engine, that has original 100bhp at 4600rpm would produce with these goodies a minimum of 15ponies more with extended reliability!
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