Since you plan on keeping the car...the good thing about SSIs is that they will likely outlive you and the car...they have great sound, provide better heat and look great...and most agree that there is a decent increase in horsepower over stock...probably 10 or more. Since you already do not have a stock setup, you may experience less improvement. Pesonally, I waited until I needed to replace my exhaust to move up to SSIs...to make it a bit less painful.

OK, maybe the butt dyno isn't all it's cracked up to be (pun intended) :D

The second best thing to SSIs are stock pre-74 heat exchangers. These sell on the used market for about 1/3 of the cost of SSIs for a decent set. If you plan to keep the car a long time then that is money wasted. Stock rusts which is why they are replaced with SSIs.

The difference in HP between SSIs vs stock H/E and a pre-muffler is not so much. The difference in torque is significant. $1500 worth of significant? That's up to you. NOTHING you do to a 3.0L for less than $1500 is going to make much difference. I tricked one out a few years ago resulting in 190WHP. Felt good but not much bang for the buck.

So given all that, I'd camp out on e-bay and pick up a set of stock pre-74 exchangers for $200-$300 if you can and try them out. If you don't like them you've lost nothing and can sell them. If you do like them then start saving your change for a set of SSIs that will last longer than your car.

good advice... but he's in Norway

the few that once existed there are surely long gone back to soil amendments...

Spend the money or don't, you can't ask somebody else their value system.

YES the SSI's totally wake up the power 4000-6000 rpm.......just like your 964 cams, they cost money, did you feel the bang for the buck.........

I spent the money, and it totally changed the car......enough said, and yeah I have the dyno charts. Yes it's spending money, and no they don't go down in value, so you can always sell them.

First, the HP improvement from the "free flow" exhaust is questionable as far as I'm concerned. The real improvement comes from the balanced SSI's.

You want hard proof. There's a related thread on the site right now. In it I linked to an old thread I posted several years back. I actually ran some before and after tests using a G-tech pro. The results are shown. They were not scientific and I didn't spend thousands of dollars insuring that all the parameters were equal but I did try to keep the before and after tests as consistent as possible. I also used a sound meter and recorded the difference in dB levels if that is of any interest.

Also, I had two dyno tests done right after I installed the SSI's. The results were within 1 HP of each other as far as peak HP. Let's just say the car dyno'd with more HP at the rear wheels than Porsche publishes as the stock crank HP. So yes, I got at least 15 HP improvement. But as others have said the butt-o-meter also reflects the improvement.

http://forums.pelicanparts.com/porsche-911-technical-forum/394868-performance-upgrades-911sc-3-0-a.html

Great!
That's all I need to know!
Thanks guys!

Otto:
I am getting worried about you. :)

You have a nice engine with 9.8 CR and 964-cams.
With high CR, you'll need to pay attention to detonation.
Search for comments by Steve Weiner and Henry Schmidt.
If you want maximum performance without the possibility of detonation, concentrate on the distributor-curve and plugs, not SSI's.
Adding SSI's vs. your current set-up will not make a great difference IMHO.

I also have 9.8 CR and 964-cams and I've tried different distributors.
Steve Weiner (Rennsport Systems) re-curved one of mine to run without vacuum specific to my engine.

Please, pay attention to the issue of curve and plugs.
I assume that the Euro distributor has vacuum advance?
Was the distributor serviced/re-curved along with the engine-rebuild?
Take one plug out and tell us what type.
Bosch W6DC or NGK6BPS ??
Or ??

Otto, keep an eye open for stock pre -74 HEs. I found a pair of new HEs for 5000 swedish kronor on the used market. They aren't stainless but after 2 years there is no hint of rust.
On top of that I found a used OEM muffler for another 1000sek and then another 1500-2000 for new oil lines, so you can do the backdate on smaller budget.

How much heat do you need?
I have a plan to buy headers and weld on a small heater box on them, kind of like this:
http://forums.pelicanparts.com/uploa...1226253856.jpg

Supposedly it will give you enough heat to keep it comfortable on cold spring and autumn days and to fight of the mist from the windows.

I hear ya!;)
I guess this is something I have overlooked. I was told not to worry about this, but I guess I should have been more skeptical...:rolleyes:
The car is now in storage, so it's not easy access at the moment. So I can't tell you what plugs I have.
The dizzy is stock for the 8,5:1 CR. And it has vacuum advance. Nothing has been done to it, except cleaning. That's all I know. Also, there is no knock, and the engine runs great. But I guess there is some more to gain from a recurved dizzy...

I'll have to investigate this further. Does anyone have a chart for a optimum curve for my setup?

Safe: Thanks, I'll keep an eye out for some used ones on the Porsche club web pages.

How does the B&B stack up to the SSI's, if you already have them. Also, have a Autothority chip. Both from my wrench on a 3.2 rebuild 90,000 miles ago. It's loud for a street only car. Wondered how different it would be with SSI's and a Steve Wong chip? Not trying to steal this thread, there are options that would help me learn as well. I would love to hear that it would be quicker and worth the expense of replacing a functioning system. Thanks, Glenn

Hey
I don't have the SSI's, that's why I was asking.

Or buy a Turbo...

When I said I already have them I meant me. Trying also to decide whether to go to SSI's, I have B&B already. Sorry for not being clear.

just my 2 cents here. just got on a set (w/ M&K 2in 1 out) moving from a bypassed system. it's worth every penny in my opinion. might be a few HP gain but it certainly drives way better in all ranges specially on low rpms. if you like to feel and hear the power then I say go for it. I also think it adds value to the car. nothing like the real sound of power through headers.

If the distributor is for 8.5 CR and was only cleaned but not re-curved, it's not entirely right for 9.8 CR.
According to the Gurus like Steve Weiner, curves are set for CR, octane and general air temps.
You don't have knock sensors and you won't hear any detonation at high revs and that's the danger.
You can check the curve somewhat with a Strobelight yourself.
Make a white paint mark on the Z1 notch and another at 33 degrees.
Set the timing to the recommended specs, then have someone rev the engine to 2, 3, 4, 5000 RPM and watch the movement of the mark with the strobe and note the degree of advance for various RPM's.
Do one set with vac connected and one without.
You want to see a steady advance through the range and no full advance before ~5k.

Here is what I observed with/without vacuum on a '78 distributor:

900 = 5 deg BTDC
2k = 16-17 w/vac 10 w/o vac
3k = 26-28 20-22
4k = ~28 25-26
5k = 30 28
5.5k = 33 30

Of course, you can affect the range by changing the starting point meaning: If you set ignition at idle at 0 BTDC, everything moves by 5 degrees.

I would really like to know what plugs are in your engine. :)

So you are saying I should not have as much advance now, because of higher CR?
I took a look at the charts for the curves on a 78 diz, and compared it to the 80 and 81- diz charts. The 80- has higher CR, (9,3:1), but the advance is a little higher than the 78. So based on this, I'd say I'm in good shape... Right?

http://forums.pelicanparts.com/uploa...1226338210.gif

Add a Steve Wong chip before you do that. If you still need to spend more money and time then move on down the list :>

This chart was posted by SW a while back on a similar discussion.

being in norway, you would probably appreciate the improvement in heat. a lot of improvement.

LA-DEE-DA

He doesn't have a 3.2, he has a 3.0 with CIS; no possibility for a chip.
His concern is about cost vs. gaining a few horses over his current set-up.
SSI's are great, I love mine but ..............there is the cost. :)

Thanks for useful and tips! (As usual)
Actually, the heat issue is not important. I only use it above freezing temps. Mainly a summer car, put on storage now. Won't be driving it until late march/early april...:( -I welcome global warming...:D

Anyone on my last question..? (prev. post)