One or two things seem to have gotten lost from this thread...
First, the primary purpose of this engine would be to last and last and last through driving conditions that are the next-best thing to intentional abuse that I can think of. Power is of secondary or even lesser importance.
Second, I am not really interested in "things you can't tell are cheating". It doesn't matter if nobody else can tell,
I would know and I wouldn't like it.
OK, and now a few responses to specific notes:
Charles, I know that it's not a problem to get pistons and cylinders of just about any size from you guys--my reply was to the idea of buying the spare set of 96es you had lying around. (Wish I could, but...)
Mueller, you may be able to take advantage of the manifold that Charles N. described. It might be very interesting to have a discussion with him and Shad about it... Also note that you can actually raise compression up to 8.1:1, since you're allowed a half-point over stock. It's just a tenth, but hey...
If I wind up with this kind of motor, I will probably just have someone (most likely Jake) just plain build it. I can supply core heads, and if he asks I can get a lot of the new parts (nice to have connections, yeah?) but I'll let the builder choose the exact parts. And have whatever profit there is from them--that is often part of making enough money to put food on the table... I've found that bringing in your own parts is a decent way to sour the relationship between you and your mechanic. Thanks for the offer, though!!
Tom, the rockers are not specified. However, I am certain that rockers with ratios that are significantly different from 1.3:1 (the nominal stock figure) are disallowed. I can see lighter rockers as a reliability improvement as long as I use the stock cam--because an engine with the stock cam is worthless above about 5200 RPM--but ones with a bigger ratio are a performance improvement and are a no-no.
Perhaps roller rockers might be worthwhile to cut down on wear? Or maybe not...
Jake, I agree that what I'm asking is non-trivial. That's why I'm not just slapping a motor together at home as we speak. And, at least from what I've read from you, the stock cam and stock low compression ratio are two of the larger problems with reliability. (And quite possibly the D-jet FI, too.)
But it's in Da Rules. A 2056 with carbs and a nice cam would instantly put me into a class where a lot of not-so-nice things will happen. First, I will have to have a full cage put in. Second, all of the other cars on the track with me will have huge fat tires (possibly real slicks?), suspensions with a lot of development in them, fully-braced structures, large 911 brakes, and so on. The ones that don't serve as "rolling chicanes" will have motors up to (I think) 3.0 liters of displacement. I think I would be in with the modified Sixes, also--not quite sure on that. A the very least, I'd be in with "#22", Newlin's 1400-lb semi-tube-frame car.
Uhhh, no thanks. I want a car I can drive to work, take off early, drive up to Thunder Hill, then spend the weekend flogging mercilessly. And I want my driving to be the limiting factor, not the car--I want a car that, on its own merits, has a chance. (I'm sure I won't for a good while, but part of the reason to do this is to get better.) And having a car that gives away 100+ HP and 200+ lbs, not to mention suspension and tires and brakes, in order to remain a street car, is not going to work for me. Not to mention having to pick up a trailer and tow vehicle because I can't legally drive on the streets. (Smog-O-Rama.) So that's the "why".
Oliver, I do know of at least one 2.0 914 motor that ran for 250,000 miles before it was rebuilt. I don't know how it was driven, but the owner did claim that he took it to the red-line from time to time. He certainly is the exception, though.
My 1980-vintage Porsche parts manual only lists one cam for all of the 914 motors, including the GB code ones. There used to be a web page (I wish I had saved the info from it!!) by Hugo from the Netherlands that had valve opening and closing points for three or four different "stock" cams that had been originally used over the years, and noted that they had all been superceded by one cam grind. (I don't think he counted the cams that were used in the later Vanagons with hydraulic lifters.) So your GB-spec cam is news to me.
The GB-spec motor also uses pistons that give it 8.0:1 compression. I must keep 7.6:1 compression.
(BTW, the Porsche manuals show the GB making 100 DIN HP at 5000 RPM, not 4500.)
Balancing all of the rotating parts, both statically and dynamically, is assumed. The balance might be to a tighter tolerance than under ordinary circumstances... (1 gram? Less?) Ditto the deck heights, chamber volumes, and compression ratios for all of the cylinders. I would think they would be set up on any reasonable rebuild, but that perhaps this sort of build would be to tighter tolerances.
I am still not sure about using lifters and pistons that are significantly lighter than stock. In particular, having lightweight pistons would make for an engine that revs more freely, the same way a light flywheel does. The lightened flywheel is only allowed in the next class up (the one Mueller is shooting for) and I believe that the lighter pistons would fall into the same category. Which is a shame because they would definitely reduce the stresses on the rods and crank...
Seat machining, at least in terms of making sure the suckers stay put in the head, should be free. But a five-angle or venturi grind on the seats is going to be a no-no.
The 911 mufflers that I've seen do not mate to the 914 heat exchangers, unless I swap to the really awful 75-76 ones. (The ones that make a tight 180-degree bend near the heads.) The 911 mufflers have two inlets for single pipes; the 914 mufflers have twin pipes going into each of two flanges. I figure a Bursch muffler setup or perhaps Triad (from Washington state) would be the way to go on that.
I had not considered a dry-sump setup. That is worth considering, as an alternative to the Accusump. I could run into problems with that if it does free up extra power. (I have heard that it takes more power to run than you gain from not having a wet sump.) Thanks to you and to Yilon for suggesting it.
Thanks for the replies!! I'm still trying to wrap my brain around this all...
--DD