Wanted 21hp from 79SC

[OldTee]

I know that this question has been asked in the past but I didn't quite know how to search for it.

Note CAT bypass already installed. Why 21HP? To get an honest 15-20 hp out of it, not marketing hp developed from advertising hype. Cost is important. I am pulling the engine in January so some cheap easy stuff can be done.

[kstylianos]

SSI's with a good muffler is the best bang for your $$. The SSI's are tuned headers and will out perform the cat bypass in every way...estimate an honest ~15 HP gain with the SSI's. More HP will require engine mods and/or an induction change.

You can also richen the CIS a bit coupled with advancing the timing about 5 degrees from stock. Cheap HP gain here.

[camgrinder]

A cam change will also increase the HP.
The Sport Sc or 964 grind on Sc are the most popular.
The problem with a 79 SC is the port size is large. Going to the
964 cam will lose torque below 4000, and increase HP above 4000.
The Sport cam will increase torque nicely but will not move the power band up like the 964 cam.
Do a search for "964 cams" on this board, there is a lot of good info.

[aigel]

SSI, cams and richen the mixture will get you there. As said above, a cat bypass won't cut it, over the SSIs.

George

[MotoSook]

Best bang for the buck is the pre-muffler, richen and ignition advance.

SSI's are not a good gain:dollar value. You are looking at $1200+ (headers, oil cross over pipe, new cross over pipe to t-stat line and a muffler) for a 12 HP gain.

Unless you are going to really build an engine, the pre-muffler will give you approx. 8 HP for about $300. THAT is a better gain:dollar value!

I would look for good used early headers before I buy SSI's.

If you are going to really build an engine or at the least the top end, you can install a set of higher compression pistons (JE pistons or used later 95mm SC pistons, add cams, and headers and a muffler. When it's all bolted together, you can fool the CIS to run a little better.

You can take it a step further and source some 98mm cylinders and pistons to build a 3.2 short stroke. You can make your own 98mm barrels with 95mm barrels from a 3.2. There are places that will bore and replate the barrels. They will match the bore to JE pistons. The alternative is to buy Mahle 98mm P/C's for $3400. Perfect Bore also makes the 98mm barrels.

Further yet, you can build a 3.4 CIS engine like "rdane" did.

Adding 7:31 gears will make it a squirty car and give you the feeling of increased torque. I think the cost of doing so varies a bit, and the feel (or gain) is harder to quantify.

You stated that cost is important, but not a ceiling.

Edit: is HP more important to you? Or is handling more important? In lieu of HP, you may consider modifying the suspension, the seating and the driver....that's if you are tracking the car.

[aigel]

Souk:

SSI exhaust ain't cheap w/ respect to hp/$, but it will deliver the maximum, just as race headers (no heat) would.

There is a reason people don't backdate to actual old heat exchangers. They are all rusted out by now, even in CA. Also, aren't the flanges different and won't match to the 3.0?

If you change cams, the benefit from backdated exhaust will really come into play. Only if you combine cams, backdated exhaust and richer mixture, you will extract the maximum power, which will be about what OldTee is looking for.

SSI exchangers can always be sold for about 75% of what they are new. Try that with just about anything else on the car!

Cheers, George

[rdane]

Originally posted by OldTee
I know that this question has been asked in the past but I didn't quite know how to search for it.

Note CAT bypass already installed. Why 21HP? To get an honest 15-20 hp out of it, not marketing hp developed from advertising hype. Cost is important. I am pulling the engine in January so some cheap easy stuff can be done.

Not sure why no one has just cut to the chase...

You can't get an honest 15 to 20 hp from any of the mods mentioned. 21HP aint happening, sorry.

SSIs are a good upgrade but that pretty much is the limit for "cheap". The rest takes cams, and high compression pistons. Neither is cheap or easy. Anything past 15 HP from a CIS engine is a struggle and a bucket of money.

[dd74]

Ummm...what's wrong with a stock 3.0?

[MotoSook]

George: Good early heat exchangers are out there. I've found two this year, one set will go on my car (on a 3.0!), and the other has been caramic coated and will be used on a 2.7.

We can go back and forth all we want, but at over $100/hp for an SSI installation you are better off losing weight and making low cost mods to the engine/exhaust. If you want to spend your money it's your business. And resale value of parts..I can think of some parts I have bought that can be resold for =/>75% of what I bought them for....the Danks pre-muffler for one.

Consider that a pre-muffler and CIS & ignition tweaking will give you 8-10 HP versus a SSI installation for 10-15 HP. Is it smart to pay the extra $1000 or so for 2-5 more HP? (keep in mind that the HP numbers are what folks have claimed and tested)

I'm not pushing pre-mufflers nor trying to prevent folks from buying SSI's, but the "bang for dollars" arguement should be made with all available mods considered.

There is a 3.0 CIS engine out there that makes 190 HP or so without spendy mods. Shed the 200-300 lbs of useless weight, and you will feel some gains.

Dane: I don't think anyone has stated that the exhaust mods will give "Old Tee" his HP numbers. I think maybe we are trying to enlighten him on what you have stated, that there is no cheap path to high HP on our engines.

Old Tee hasn't responded and his statement of cost being important is perhaps what has led to the cheap exhaust mod discussion. Surely cost is important, but does that mean he wants to build a 3.4 like your's for less? It won't happen, but if he wants to modify the topend with cams, pistons, head work and add exhaust, he will see better than 12-15 HP gain within a median cost region.

[dd74]

In following up Souk's argument I saw on one of this year's earlier dyno days posting by RDane that very little horsepower gain was netted by the installation of 20/21 cams in (at least) a late 3.0 - all of 5 horsepower. This 3.0 as well had SSIs and a Triad dual-in-dual-out exhaust, and also was recently rebuilt. Its horsepower was 198.

Remember: SSIs are the best "new" heat exchanger/exhaust manifolds available for the 911, and 20/21 cams are the most radical cams one can use while retaining the CIS fuel system.

Given that a same model 3.0 without the cams, and with pre-1975 heat exchangers has been recorded to make 193 horsepower, one should second guess the thousands of dollars involved to gain only 5 horsepower.

In all, when I asked "What's wrong with a stock 3.0?" I asked this from a practical sense. I've seen quotes approaching $4,000 to modify the CIS and install 20/21 cams. Tack on another $1K for SSIs, and another $500 for a known muffler. Give or take $6K and you have 15 more horsepower than a stock SC motor. Is that practical? Of course, with an earlier 3.0 (78-79) you'll have a bit more power, which might have to do with the larger induction system, but still, the bottom line is the hp-to-$ ratio, which does not lean toward "value."

RDane is correct when he says "dream on" (sic) about getting 21 more horsepower from a CIS-based 3.0. Now you're in to tear-down territory with your engine, and might as well do a whole host of "additions" that will make spending $10,000 worth your while. Hence, if it ain't broke, don't fix it.

I believe the 3.0 engines are designed (stock) to an optimum point where race motor meets street motor. They're not V8s or Japanese motors. They don't allow cheap horsepower upgrades. Your best bet to gain a more lively ride is to lighten the car and do suspension work. Even before that, you should learn the car's parameters on a race track. A stock SC (or any 911) might be far beyond your driving talent, and could consequently be asking you for a "driver upgrade."

[rdane]

Same day dynos and at the wheel numbers for various SCs.


'79, mods are SSIs, Dansk 2 in and two out and a Webcam 20/21.
Car is well tuned, 190K miles
182 hp and 170# of torgue

'79, mods 1in/2 out Flowmaster.
168 hp and 162# of torque
adding SSIs gave 177.1 hp and 161.8# of torque
High mileage engine with a very recent tuneup.

'81, mods SSIs with a OEM 2 in/ 1 out.
159 hp and 169# torque (check the torque numbers again on the pricey '79) High mileage engine

'83, mods '73 OEM exhaust, Triad 2in and 2 out muffler and a Webcma20/21 grind. Engine was recently rebuilt to factory spec and is now well broken in.
173hp and 174# of torque.

This is a good comparison for the early and late SC heads and the 8.5 and 9.5 compression pistons used on each and also a good comparison of the SSIs and early pre '74 exhaust. New engine and one with 190K miles! Give a person reason to ponder SC upgrades.

[sammyg2]

I got around a 70 hp increase for $1200, beat that!
Sorry, couldn't help it.
i have a question tho, prior to bolting on the forced induction I replaced my cat with a cat bypass pipe. It sounded a little better, and felt slightly stronger, but barely enough to mention. Is a pre-muffler really that much better than a cat bypass pipe? From what I've read in certainly appears so, I'm just looking for confirmation. Tanks.

[camgrinder]

Rdane,
If its not too much trouble, could you list the RPM where the peak HP and Torque numbers are?
Do you have any numbers for a factory stock early and late engine?
Thanks

[MotoSook]

Oh yes..you can add a used BAE turbo kit or build one...Richard Fong has abandon his turbo kit I believe. Yep, Sam, that is probably the BEST bang for the buck.

[dd74]

Camgrinder - here is a late SC engine with '74 heat exchangers and dual-out exhaust.

[OldTee]

Thank you. I have been following this discussion with much interest. I am starting on a weight reduction program, with the A/C leaving now. I have rebushed and added new Bilstiens. All new brakes. Turbo tie rod. The 79SC has 138K with a rering top about 10K ago by the PO. Most of the bugs have been worked out of the CIS. One noticable change was new injectors. Gave quite a kick.

I like the idea of a cam change. I have a question about backdated heat exchangers. I thought the 3.0 was a larger (maybe longer) engine than the 2.0 or 2.4 and has larger cylinders.

There is some good thinking going on here. Thanks again.

[rdane]

Originally posted by camgrinder
Rdane,
If its not too much trouble, could you list the RPM where the peak HP and Torque numbers are?
Do you have any numbers for a factory stock early and late engine?
Thanks

Sure...here ya go John. From the numbers posted above.

'79, mods are SSIs and a Webcam 20/21.
182 hp @ 6400 and 170# torgue @ 5500

'79, mods 1in/2 out Flowmaster, oem ex, CIS cam
168 hp @ 5600 and 162# of torque @ 5000


'81, mods SSIs with CIS cam
159 hp @ 6100 and 169# torque @ 4200

'83, mods '73 OEM ex, 20/21 am
173hp @ 5800 and 174# of torque @ 4000.

My dyno storage
http://quelle911.com/phpBB2/index.php?c=3&sid=44aca8fe9c1b21565aeaff7c7e1fae7a

David the sharp peaks on the end of your dyno are from putting the clutch in on the dyno run. They are not your true values. Your peak torque number would be correct. Your Hp peak is more like 160 or a bit less. Noah has a similar fluctuation on his posted dyno graph which skews his number as well. Dyno operator just didn't take the time to explain it and run a better one for you.

Your's pretty much duplicates this run with less money spent for mods
'81, mods SSIs with a OEM 2 in/ 1 out.
159 hp and 169# torque (check the torque numbers again on the pricey '79) High mileage engine.

One noticable change was new injectors. Gave quite a kick.

Good catch. Most ignore the fact that these cars are running 25 year old injectors. The new ones are much better and cheap to replace along with all the CIS seals. It made a big difference on my 3.4 I suspect.

[dd74]

Actually, I've had new plugs, rotor, wires installed, and a timing adjust since then, so if it wasn't at 164 rwhp then, it may be there now, if not a little higher. As well, this dyno run was in third gear when most dyno runs are done in fourth, and supposedly yield higher numbers. However, with the clutch, yeah, I can see that - I've wondered about that end spike too.

Darn dyno rookies. Darn them all to hell!