I'll go back on topic after this first bit I promise - so what if someone makes a bunch of posts about various engine combination ideas/plans, and then they change them. This can happen because the discussion ended up bringing up a bunch of issues that made the particular combination more or less suitable to the original goal. And that's a good thing - wouldn't you rather 'map it out' here and find that a bunch of people with various experiences can say 'well this is what they don't mention, or this is a pitfall with that combo, or whatever' . surely that's what this group is all about - the sharing/fine tuning of information, to save us all thousands of dollars and hours of heartache! Sometimes the plans don't change, the situation does. I started gathering everything I needed for a supercharged a15 setup for my coupe. Then work slowed and more or less dried up and for a couple of months I was really struggling, and had no choice but to sell off various parts I'd amassed (often at a significant loss, because a bill came in and I had to pay it). Thankfully, I'm doing something else for a living now, busy as can be, and happier than ever. As a result, in the last 6 months I've started to re-build the collection of bits and pieces I need for the conversion. So instead of it taking perhaps 6-12 months, it took a good year plus to gather the parts, and then another year saw them slowly disappear (even when I started the new job, I still had debts to sort out) and now a futher 12 months or so to re-gather what I need, and 'then' I can actually start on most of the work. During this time, the car's gearbox let go, luckily, I knew it was on the way out, and grabbed Marty's 5 speed 60a box he had for sale, just prior to that, and could use that in the mean time. but it wasn't cheap, so that put any progress on the 'final project' on hold again for a little while. I've been ripped off by one person off the bluebird forums who loaded a gearbox (that I drove interstate for) into my boot late at night, and decided to keep the tailshaft yoke and the shifter from it. apart from that breaking the deal, it also leaked oil in the boot area that took a month to get the smell out. On the other hand, pretty much everyone I've dealt with here (maybe a hiccup along the way with one thing but the guy stepped up and sorted it, and I'm appreciative of that big time) has been decent.
These things take time, and even doing it 'on the cheap' take money. Meanwhile most of us have rent, or mortgages to pay, kids to feed and a hundred other things, it's just the way it goes. Naturally we get to the point of doing 10 times more discussing than building on some things, because in the end, we can only afford to do it once, so we need to get it right the first time.
but back to the topic at hand:
Prompted by the news that the 'genuine s/c oil is so ridiculously expensive' from supafatto - A while back I mentioned Shell donax TD oil - as being about as good as it gets for both any manual gearbox (it is used in a range of heavy agricultural machinery drivetrains) and also it would be excellent for these superchargers (and btw I'd avoid using diff oil in these chargers, there's no hypoid gears in them, and as such, they don't need the additives/combination that diffs do, and the additives to make stuff survice in a hypoid gear arrangement, aren't as ideal for regular gear/drivetrains, and also are potentially corrosive, if not to the gears and bearings, then possibly to the s/charger seals. Some seals handle diff oil fine, but not all do). If it's good enough to protect the drivetrains of equipment costing more than all our datsuns put together, believe me it'll work on our boxes and superchargers (it's around a 10w30 too if anyone cares. By the way - 'thick' diff oil at 80w/90 is actually 'rated' on a different scale, so it's nowhere near as thick as those numbers might suggest. At 100c (and in a supercharger you'll see temps soar over that) it can go thinner than 30 weight motor oil. So under actual high boost/stress situations this oil will not deteriorate in film strength as much as diff oil might.
Anyhoo- that oil was superceded by shell, who have simplified their range. so I didn't know the 'new' name for it. And then I didn't know the price either.
I've found the name, it's now called shell spirax S4 txm . It is available in eith a 20l or 209l drum. the former costs around $170 for 20l and the latter is somewhere around $1500 or so for the 209l. Obviously for a big farming or heavy industry 'fleet' you'd go the big drum, but a 20l would last regular guys years. I picked up some recently from blackwoods (mostly because they could get it in and they are literally just around the corner from where I work)
It works out to about $8.50 per litre. Which is way cheaper (by volume) than 'official' supercharger oil. If anyone in melbourne wants some for their supercharger, or even for their gearbox, I'll happily do small amounts at cost (if the buyer provides the container to put it in)http://www.blackwoods.com.au/PartDetail.aspx?part_no=00520242
They'll happily order it in for you, but if you don't have an existing account, it'll be strictly full price paid up front before they will order it. From the time I put down the cash it was approximately 2 weeks (give or take, but there was a long weekend in there to complicate matters) to the time it was there ready to be collected.
On the original question - I absolutely think the SC14 is the go for sure. You'd 'get away' with an sc12, if you weren't chasing really high boost levels and or rpms. Technically the sc12 could handle the same blower rpm as an sc14 (I would suspect, based on their design and how their difference in pumping capacity is achieved) however, since they pump less volume, the drive ratio from engine to s/c would need to be higher to get as much boost, so they'd be running into rpm related issues sooner, so to speak. Don't let me make this sound like doomsday for the sc12 - it certainly isn't and they feed the 4agze motors quite capably (a 1600cc motor after all)
There's certainly some call for head studs, but I'd also (just thinking out loud here) wonder if maybe stock head gasket and head bolts (provided they are in good condition) might not be a good idea for starting with. That way, if you get the mixtures badly wrong, or run too much ignition advance at full boost/rpm, then the head-gasket can 'blow' like a sort of 'safety fuse' rather than damaging pistons etc. Obviously you still couldn't run it into detonation or pre-ignition for extended periods and have it survive, but if you were careful with the tuning/optimising and stopped when it blew the head gasket (or when you discovered it was blown) then you could 'go back' a little richer or a little less ignition advance - replace the head gasket and you're set!
I definitely echo the other people's mentioning in the thread - water injection works and it works very well. It's cheap too (you can do it without having to buy a commercial kit, and would be able to put together a very decent setup with a high pressure pump off ebayhttp://www.ebay.com.au/itm/SHURFLO-20 ... ories&hash=item2a1eccb6d8
or similar (45psi would be plenty, and most good nozzles work well at 5-10psi (so if you had 15psi boost, you'd need 25psi, to inject in the manifold after the supercharger, but you could also inject before it, which means there's no boost pressure to overcome to spray the water, and it will also cool the lobes in the supercharger itself, so can help it run cooler.
A hobbs pressure switch (around $50 on ebay, depending on what you need - it'll definitely want to be a 'normally open' one, and the switching pressure - 4psi isn't a bad place to start, you might even run 2 - one at say 4psi, and one at I dunno 15 psi, the first would power up the pump (or you can run the pump all the time as it internally switches off whenever internal pressure is up around the cutoff 45 or whatever psi. Just like on those karcher pressure washers - they are 'always' on but they switch off internally, then you pull the trigger releasing water and the pump re-engages the minute the pressure drops below 45psi or whatver). Anyhoo, you could then run a solenoid so that there's an extra injector fed in addition to the first one as boost goes above 15psi or whatever.
FOr injectors - you can get agricultural spraying nozzles and fittings and run something like that, and they work well. Or you can run efi style injectors (that can be switched on and off as needed. They won't last forever spraying water, they will corrode. But if you got injectors from a wrecker and replaced them every few months it'd be cheap. Or alternatively you can run injectors that have a stainless steel pintle internally and won't corrode. IIRC they came standard on some particular mercedes models. No idea as to cost to buy them aftermarket (and I wouldn't buy em from mercedes benz as that'd likely be the dearest price for them anywhere)