quattrorunner

Hello all.
I am going through the initial thought process in order to decide how I will be building my 911 sc engine. I have a 79 sc and it runs very well although I have yet to get a compression and leakdown test. I want to do the rebuild and want to consider putting it back together with turbo headers and such. The question is for those who understand the 911 engine paramaters like how much a 911 sc could be boosted if intercooled I know 8.5 or so compression on any modern car is plenty low for some good boost levels, but get the idea that it may be a little high for the 911 combustion chamber? Is it pointless to boost the sc or are there other things to do without replacing the pistons in order to get say 10-14 psi? I really don't want to get crazy like water injection or methonal or any crap like that as the car needs to be a good streetable car. I just want some boost but don't like the idea of melting the heads or pistons. Has anyone added metal head gaskets to rise the compression on a 911? Does that sound idiotic? It's cool, just let me hear it. I was reading about alusil cylinders and think I probably have these. I do want to check the rings so What should I do there? Has anyone done Dry film lubricant on these cylinders? How about coating the tops of the pistons for heat dispersion?
I really just want a kick *** engine that I can be proud of. I'm not trying to set records, just build a good reliable 3.0 engine that is strong and special. I don't think it would be worth turbocharging unless I could reliably get 9-12 psi. I am thinking of EFI as the fueling. If I couldn't do that, I would just build it a little hotter than stock and make it look super sharp in the process. Like I said, I want something special. Keep in mind that I would like to keep the origional p&c to keep that cost in check. Afterall, I'll need to save up for all the turbo components Thanks, and I know there are plenty to respond to with this topinc so just take your pick and respond anything. It's all helpfull.

racer

um.. they call the "boosted" SC a 930! Seriously, you would be better off buying a complete used 930 motor than creating your own "turbo" motor. But, if you like projects and spending more money, at least use the 930 specs as a guide as you build your own.

Edgy01

Been there and done that. It resulted in one of the best running 911s I have ever owned. Mine started out as a 1981 911SC, and had a Rayjay turbocharger added to it before I bought it. Ultimately I melted #6 piston one morning when I was a little shy on octane so I had the engine rebuilt.

Recall that the SC engine has a fairly high compression ratio to start with so you can't go too overboard with the boost from the turbo. I wound up, during the rebuild, shimming out the pistons a bit to get the CR down. Ultimately, what made it run so much better, was having the distributor curve relined. You need to do that sort of custom work since you are making such a difference to how the engine runs.

The car began as a simple 911SC with 172HP and wound up with a solid 270HP,--easily,--and not intercooled, either. I ran it with a whaletail,--one of the orignal ones just after the duck tails. (Not the big intercooler accommodating ones). I welded on a fastener to the boosted tube (up high) and then screwed on the boost sender and put in a 930 tachometer so as to see the boost data. You also MUST glue closed your toilet flap if you have one,--the CIS airbox protection. (Many of us, you may recall, have that flap in there to save your airbox in the event of a backfire). I simply used GE silion to do it. BUT, you must remember that it is no longer protected and you must make sure that your fuel pressures and the fuel regulator are perfectly maintained from now on.

Do not push your luck by taking this mod to any extreme. I had them put in the turbo/930 oilers for the piston crowns, and I ran it with a Carrera RSR pressure plate to handle the extra HP. The 915 tranny will handle the new found HP quite easily. (They can handle a heck of a lot).

When I did the shim work I was finally able to ween the car off Premium AND Octane 104. From then on it ran on simply premium. Downstream of the turbo was simply a exhaust pipe that curved under itself and exited the usual location. There was no muffler (as there is neither a need for one nor room any longer). You are highly encouraged to run only Mobil One from now on. Anything other than synthetic will wind up coking the turbocharger bearings. So,--do a slow warm up and a thorough cool down before you shut it off. I ran a conservative 6 psi of boost and got tremendous performance. CR was estimated to be around 8.3:1. (No catalytic converters, either). You stated a desire for 10-14 psi,--you have a LOT more work to do to get to those numbers.

The car EASILY pulled to redline in 5th gear which translated to 162 mph.

The folks that did the work,--BRI Imports in OKLAHOMA CITY. (405) 848-1961.

Dan

quattrorunner

Thanks Dan, You get it dynoed? That sounds awsome! Sounds cheep too. In the engine build, I plan to upgrade the squirters and all upgrades the 930 has plus more. Intercooling will be a must for me. Your car use 930 exhaust?

Porschefile

I'd say either buy a 930 motor or try to convert to the stock Carrera 3.2 EFI. Protomotive is pretty good with the 3.2 EFI, and you could do chips and possibly a turbo kit from them for a relatively inexpensive price. Or, you could buy this Protomotive Motor

quattrorunner

OK yeah. That motor is the final step years down the road. It's more valuable than my car with a rebuilt engine in excellant shape. Thanks but I would have to sleep with it as well.

Edgy01

Never had it dynoed as it's so subjective. We conservatively rated it at about 270 hp. Several years ago we did a little test between it and a new Carrera (3.2 in those days) and we both started in 5th gear, at 60 mph and floored them together. The turbo car started walking away around 120 mph and never looked back.

It is a relatively inexpensive way to make the car go fast. The exhuast system was not from a 930. It was from the Rayjay kit,--merely a larger diameter tube with a single 180 degree bend in it, exiting the usual place. The sound was great,--and then the blue flames were a bonus!

dan

quattrorunner

Cool. Anyone have any experience with mounting the turbo closer like in the fender? Why not? Thanks.

VZ935

I tend to agree with racer .. I think you could buy a used 930 motor and sell your existing 3 liter and end up with a better , more cost effective package.
Whatever you do , just as ling you get the performance you want in the end it's all good !

Edgy01

I'm not sure where you are thinking. The issue of turbo lag becomes larger and larger with the greater the distance between the turbo and the CIS intake. My aftermarket rig was positioned just like the factory turbo (just beneath the distributor) and turbo lag was minimal. You really can't move it any closer without compromising the introduction of heat into the engine area. You want the turbo, well shielded by engine sheetmetal, etc. down in the slipstream.

Dan

VZ935

Actually I did put my turbos off to the side of the engine and therefore had a more direct shot from the intercooler into the cold side....

Edgy01

You can certainly do that but you have been willing to go further with changes to the engine compartment. My modification was non-invasive, and only required a minor tailoring of one piece of engine sheetmetal,--the one directly beneath the distributor.

Dan

quattrorunner

V2935,
I would like to be confused with your app but must say mine is much more white trash in execution. I mean, I would love to see more photos of the finished car in total. The engine photos are awsome. I plan to spend as much as one of your wastegates total.
Edgy01, Thanks for your input as well. This is something I hadn't considered, but is this the only reason? Thanks, BA

quattrorunner

Racer, have you checked the prices for a good complete 930 engine? I understand your comment and would agree but I feel it would be cheeper to build mine with more modern components like a garrett or turbonetics style turbo to start, and just add ricer accessories that work. I don't follow this sport compact ricer scene really but I am a car guy so I can't say my eyes are closed to what is going on. And I have seen some of these cars putting good HP numbers down. The parts used to accomplish this are less expensive and more modern in apperance and application than what the 930 has to offer. I hope to build something nice and effective without going to double digits. I think it can be done easily and I intend to try. Any thoughts? I know that there are modern components for the 930 even good upgrades like the k27 which is not new but effective but the cost for it is a bit funny. I guess I'm trying to say that I want to go a differant route than is normal for a 911 turbo owner for more power. I don't expect to get over even 350 crank hp anyway. With scock sc gearing , flares and brakes to start it would be unwise to think otherwise. Later on, maybe I'll feel the need to make it hot but first things first. 350 crank hp is almost double what the sc has so I think it will be good upgrade. I am keeping my eye out for a stock 930 exhaust.