How can I get more power from an SC engine?

[earlyaircooled]

I'm thinking about buying a 1978, 911SC. I have known the car for years and it is a sweet, original 105,000 mile car, runs great. If I buy it I would like more power, but not interested in a complete rebuild or tear down of the engine and I want to keep the air cond hooked up. Looks like it has the smog pump thing, can I simply unhook it or do I need to do other mods to get rid of that? Will a better free flowing exhaust make much difference. IF so what kind, brand etc. Any suggestions, especially those with estimated costs would be appreciated.

I've always loved SCs but they seem lack luster in the performance area, how can I wake it up?

Attached is a picture of the engine.

Thank you,

Davi d Hanning

[Joe Bob]

SSI or early style heat exchangers, aggresive cams 964 or hotter, dump the CIS and go with an modern FI or PMO carbs....

[javadog]

That pretty much sums it up. Changing the heat exchangers ( and the oil lines needed) and installing a good sport muffler will set you back a couple grand, if you do the work yourself. Cams can be another couple grand, more if you add springs, less if you have yours reground. Plus any labor, of course. Carbs start about 3 grand and go up from there, depending on options. All this might net you another 30 hp, on a good day. You can change the pistons and cylinders for a few more ponies, but that alone will cost as much as the above. Maybe 20 more ponies.

You can build a real nice engine if you want to spend the dough to do it right. I have a buddy that had Henry Schmidt build him a motor. Close to 300 hp but north of twenty grand to build. A work of art.

Ditching the air pump makes it easier to do a valve adjustment. In a nut shell you yank the pump, the brackets and lines and then plug the holes the air lines came out of.

JR

[iamchappy]

Start here: best bang for the buck.

911SC Turbo

[Steve@Rennsport]

Here are some ideas:

1) Easy bolt-on stuff that makes a difference such as SSI's with a good sport muffler.

2) Build a big CIS motor such as a 3.4 or 3.5 litre one. Those are smog-compliant, make a ton of torque, and are very docile. Its not cheap, but reliable HP never is.

[tcar]

Be sure to check your state's smog regulations before ditching the air pump.

Ditto the CIS injection. You don't have a catalytic converter (air pump instead) on '78 - '79 SC's.

[munsonbw]

If you are handy, you can get the performance of the SSIs for less than half of what was mentioned here. I used pre-74 heat exchangers and old oil lines for less than $500. I used a Dynomax cross flow muffler, $125 with flanges and mandrel bends. Sounds great, costs less. Not as nice to look at though.

If I did not have a Euro with 9.8:1 CR, I probably would have gone with the turbo. You could easily fab a system for under $1000 and have three times the gain of SSIs.

Be ware of new cams, pistons, etc. The slope is VERY slippery... Cams, resurfaced rockes, gaskets, rings, it all adds up fast.

[ZOA NOM]

Get a Carrera instead.

*enable flame retardant mode*

[earlyaircooled]

To all that have posted here so far, thank you. I still welcome more ideas.

Thank you,

David Hanning

[RWebb]

What you really need to do is to post how much moola you are willing to spend.

2nd we need to know HOW the motor is going to be used.

If you want to spend - say- $200 you are SOL. If you are willing to spend anything but will use it on the street, then a 993 RS 3.8L swap is what you want. If you are restricted by race class rules to 3.0L then it is something else again.

Remember, it is a Porsche motor not a 1960's Chevy -- that means more hp is not cheap.

[RarlyL8]

[earlyaircooled]

Initially I would like to budget $2000 for engine performance gains. I already have a nice set of early heat exchangers for that modification. What next?

Thanks

[Kevin Stewart]

3.6

[munsonbw]

~$700 will get you 964 style cams (yours reground), resurfaced rockers, and the required gaskets, etc. If you don't have tools to work on these motors, figure $300 for the 911 specific stuff. That will put you at ~$1000. Maybe add stiffer valve springs to increase the revs, $500? If you haven't replaced the Dilavar studs, do it while you are there. That pretty much burns up the better part of $2000. Leave the last couple hundred for misc. other. This of course assume you will do the work and not do any engine overhaul. If you want to do that, then others will have to chime in. Probably another $1000 for machine work to the heads and cylinders? Might as well increase the CR with some JEs for another $1000. Of course, you do that and you can get away with a little wilder cam and still keep the CIS. Drop in carbs for $3000+.

Or... the turbo for $1000 or so. This will require you to do some fabrication, but many have been there, so it should be reasonably documented.

I'll offer my opinion even though not really asked for. Building a 911 for more power costs a lot of money really fast. You can easily spend your $2000 and get about 30 hp. To me, that is a lot for a little and why when I did my head studs I left the cams alone. Ask some guys what they have in their 3.2SS that make about 250 hp. It is a lot, and hard to justify if your motor runs well, or you have a bigger budget. I have the luxury of a Lotus 7 clone that costs next to nothing to upgrade, so my "scary fast" costs much less. Do you have anything like that? Focus on the easy mods listed and drive your car on the track. Learn to use its handling abilities to go faster. Drag cars these are not. I had to face that reality not long ago. Porsche just didn't leave gobs of power on the table with these motors.

Cheers,
ben

[earlyaircooled]

Hi Ben,

Thanks for the thoughtful words. I guess an SC is a great car but not really a hot rod unless you strip the weight and put in a bigger motor but then it really isn't an SC anymore. The fastest car I've owned was a modified 944 turbo and that car was scary fast to me. With the low cost of those I could get this SC keep it stock and pick up a decent 944 turbo for $5000-$8000 a little later and they are easy to make fast......It is a good idea. I can still use the SC for track days to build my skills to really learn to drive a 911 and the 944 turbo when I want to scare myself and feel those accelerations Gs

One more thought. From previous posts to this thread sounds like I could add the earlier heat exchangers and an EFI system like the Bitz racing Mega squirt and add about 40 horsepower at the crank and better throttle response for around $2000. Is that a difference I would notice, would it be worth it in other words?


Thanks again to you and all who replied,

David

[911nut]

Speed is a virulent sickness for which there is no cure!

You would notice a 40 HP bump but after a few drives you'll want more.

I've been down this road; I wanted to put a 3.6 in my old SC but between that and the paint it needed I would have been so upside down with $$$ it didn't make sense.

So I bought a Turbo. It's stock but I still enjoy it. Problem is I'm already making plans to up the HP on it. Turbos are as expensive to hot rod as normally aspirated engines are.

Bottom line is buy what you like and plan on spending $10k for meaningful HP if you are a hot rodder.

[munsonbw]

David,

I seriously doubt that you will get 40 hp with the exhaust and EFI. I would think 30 would be doing well (as per 911 performance handbook). There is much debate about how much hp you really gain with the SSI style exhaust. I think there was a thread with several dyno runs and if memory serves, the consensus was low teens in some cases and single digits in others. Where you really get the benefit is the midrange torque. Unfortunately, when I was backdating my exhaust I found the head studs broken. I put off the rebuild in favor of other summertime activities, so I hadn't driven the car in 4 months. It is hard to say what reading I am getting on the "butt dyno" (it is broke with a crack in it ). I have noticed more punch in the midrange. I never used to be able to break loose the tires from a rolling start, I guess because of the LSD. Now, if I catch it just right it will step out a little. Also appears much easier to hang out the rear end taking off from a stop and turning. It may sound silly, but I am as happy about the sound improvement as the perceived increase in power. My old exhaust was shot, so the upgrade had many reasons... the muffler choice was for sound.

As for the EFI conversion, there are better qualified people to answer this point than I. However, what I hear about carbs is midrange throttle response. I don't think there are very large WOT hp gains to be had, and they are certainly smaller if you keep the CIS runners and throttle body with the Tbitz or similar. But, what you will get is a system that is less "fussy" once set up and quicker throttle response. This should be similar to the gains that Bruce Anderson mentions about carbs; they feel like much more than they are really giving.

I certainly don't want to discourage you from making upgrades in the name of performance. But, you mention getting a 944 turbo for $5-8k. You can easily have that in a 911 motor to get in the 300hp range. I feel the key is to be real about how much you are willing to spend and when. Penny wise upgrades now may end up useless down the road when you search for the big gains. 964 cams are not a good choice for making bigger power. In fact, these really only make a few hp or so, but they are said to let the engine breathe better in the upper revs and not fall off so soon. That is really more about usable hp that a dyno number. You have a good engine to start with. The '78 has the 39mm runner and intake ports. Advancing your cams and looking for some good used later CIS pistons with 9.3 or 9.8:1 will put you in the range of my car, a RoW 930/10 motor, with 204 hp + what ever I am really getting from the exhaust backdate. Couple that with your early HEs and for <$1000 you should gain 30hp over your 180 pretty inexpensively. Certainly the cheapest without a turbo I can think of.

Hope I didn't ramble too much. Don't forget, the cheapest way to go faster is to add lightness.

Ben

[Kroggers]

Subscribing. I am interested to know what answers you get to this as well. I have recently found out that the yearly inspections here in Sweden will fail you if you do an engine upgrade - increase the Hp. So I will have to do it inside my 3.0 If I want to keep the car on the road, and hope they never ask for a dyno reading

[burgermeister]

Probably not what you want to hear, but if you want acceleration a pre-1990's 911 is not the right thing to get. The cars are great fun to drive, and presumably great on the track (no experience here), but by today's standards they are pretty slow on the street. You'll spend a ridiculous amount of cash upgrading, and still get toasted by most (much cheaper) factory hot-hatches, vettes, and V8 Mustangs.

Buy it for the handling & feel, not the power, or you'll never be happy with it. Unless you have that extra 10 or 20 K to spend, of course ...

[munsonbw]

I may have left out an important detail in trying to recreate the Euro spec motor: they have a different fuel distributor than US cars. Not sure if the US version can be adjusted to flow the fuel required for the extra hp or the euro spec or not. The FD is probably a factor in getting 204 vs 180. They are hard to come by and are a little pricey, maybe $500?

Don't forget if you are dead set on a 911 and drag racing, you can always sell your motor for $4000 and buy a V8, Subaru, or RX-7 rotary turbo. For the money you get for your motor you should be able to cover the new motor and conversion kit. You will get flamed till no end here on the board from purists, but it is really cheap power. Not really different than putting a 3.6 in there, but it is perceived as putting a Ford motor in a Chevy. My personal choice would be a WRX or one of the RX-7 turbo motors from Japan if mine ever grenaded. It becomes a bastard and you will have to be committed to owning it for life or loosing money. SCs are a dime a dozen though...