Should I bother installing SSI's?

[otto in norway]

Hi

As the topic says, should I?

My reason for asking this, is that I already have gotten rid of my cat, and replaced it for a pre-muffler. Also, it has a big sports muffler on the back. So I guess I have some HP gain already, although, I do have the stock heat exchangers still.
I should explain that my engine was rebuilt this summer, and have 964 cams, and pistons with 9,8:1 CR. So that will probably make changes to the exhaust more apparent, right...?

So, what do you think?

[Vipergrün]

Absolutely. Go with a 2-in/2-out muffler. Check out M&K exhaust. These changes should really open up your motor!

[richde]

On what engine?

[Vipergrün]

Sounds like a 3.0 based on his upgrades....

[otto in norway]

Thanks, but how much REAL difference will it make? 10 HP?

It is a '79 911 SC, 3 litre engine. As previously mentioned, it has 9,8:1 CR, 964 cams, Fabspeed pre-muffler, sports exhaust, but stock heat exchanger.

[Vipergrün]

Hard to say what the actual figure will be. Seat of the pants should feel much better, though. You should also get better power throughout the RPM band

[otto in norway]

OK...
I guess the real gain is made from the headers, that will give less resistance...?
Hence "free flow"....?

[Gunter]

SSI's would balance better but you would probably not notice much improvement unless you go straight out with a 2in/2out muffler but.......................
All 2in/2out mufflers have a very bad drone/resonnance between 2-3k that will drive you nuts.

I've tried M&K, Dansk etc..............and it's just disgusting.

2in/2out are great for the track but not for street-driving.

With 9.8 CR, concentrate on mixture, timing and octane to prevent detonation!
What is the curve on your distributor?
Is it a Bosch 0 237 306 001 or 0 237 301 007 or 0 237 301 009 ??
What plugs are you using?
Bosch ???

[kiwiokie]

Originally Posted by Gunter

All 2in/2out mufflers have a very bad drone/resonnance between 2-3k that will drive you nuts.

I've tried M&K, Dansk etc..............and it's just disgusting.

My easy fix for this is to flex the right foot more and you pass through that rev band before you know it. I just had SSI's and a 2 in 2 out M&K sport muffler installed and love the combination. Cheers, John

[fintstone]

Better heat from SSIs too.

[Joe Bob]

Do it....nothing out there better with heat....except maybe early OEM equal length HEs.

[RarlyL8]

We just installed a set of SSIs on an '89 Cab and a Cat Bipass Pipe on an '89 Coupe. They both drove identically when stock and now the Cab edges out the Coupe in seat of the pants torque.

[otto in norway]

OK...
"Seat of pants", you tell me!
But is there any hard figures to back it up?

As I mentioned, I got a "free flow exhaust", except from the heat exchangers....
So... What would I gain, realistically speaking..?
I now have a great car, but I'd like some more!
(It's addictive)
I'm not gonna spend $1500 for a few HP, unless I get 10 - 15 HP more...
What do YOU think!?

[Joe Bob]

Originally Posted by otto in norway

OK...
"Seat of pants", you tell me!
But is there any hard figures to back it up?

As I mentioned, I got a "free flow exhaust", except from the heat exchangers....
So... What would I gain, realistically speaking..?
I now have a great car, but I'd like some more!
(It's addictive)
I'm not gonna spend $1500 for a few HP, unless I get 10 - 15 HP more...
What do YOU think!?

Then buy a 3.6, swap it in, sell the 3.0.....it's a smog engine that has antiquated FI and exhaust. Geeez, what ya expect? It isn't a Chevy where you can add an Edelbrock double pumper carb and headers and get 100HP.

Next you'll be asking how to get the 915 to shift faster.....

[otto in norway]

Originally Posted by Gunter

SSI's would balance better but you would probably not notice much improvement unless you go straight out with a 2in/2out muffler but.......................
All 2in/2out mufflers have a very bad drone/resonance between 2-3k that will drive you nuts.

I've tried M&K, Dansk etc..............and it's just disgusting.

2in/2out are great for the track but not for street-driving.

With 9.8 CR, concentrate on mixture, timing and octane to prevent detonation!
What is the curve on your distributor?
Is it a Bosch 0 237 306 001 or 0 237 301 007 or 0 237 301 009 ??
What plugs are you using?
Bosch ???

I don't know anything else than that the dizzy is stock... The plugs? dunno...
They came along with a service bundle parts shipment...
I have adjusted the mix to 3,5% CO at idle (at 950 RPM and 5 deg BTDC)

[otto in norway]

Originally Posted by mikez

Then buy a 3.6, swap it in, sell the 3.0.....it's a smog engine that has antiquated FI and exhaust. Geeez, what ya expect? It isn't a Chevy where you can add an Edelbrock double pumper carb and headers and get 100HP.

Next you'll be asking how to get the 915 to shift faster.....

Ok... ...Relax!
I'm NOT stupid! I know about the 915 problems, and will be doing some work with that this winter...
Anyway:
This is why I ask this question here!
Because I am not made of cash, I'd like to know, if what I'm going to do to my car, is really worth while...
(I already spent a few bucks)

All opinions are welcome!

[Joe Bob]

I'm T O T A L L Y relaxed.....but you have to realize that the 3.0 and 3.2 have limitations that are built in. One is the cams, next is the FI and the other is the exhaust.

Doing the upgrades is not cheap and neither are the parts. Unless you do the labor yourself you will price the upgrades up to the level of Steve Wilkerson and the Gold Plated Porsche fame.

The Fuel Injection cam is limiting due to smog restrictions...simply putting carbs on it usually just pissezzs off the engine. It sounds nice but you lose MPG and get minimal HP gains....doing the exhaust helps....going with 964 cams was my best upgrade.

Then I just sold it all and crammed a 3.6 in my SC except for trashing the 915 due to increased torque and my heavy foot on launches, it's been a blast.

How fast do ya wanna go and how much $$$ do ya have to spend.....

[otto in norway]

Alright..
My plan is to make the most of my engine as it is... (NA)
BUT I'm not gonna spend a lot of bucks on an upgrade, that I won't really feel... 1500$ is not cheap!

I've test driven a '84 carrera with a 3,6 with 915, and I gotta say, although it went better than mine, I'm not way off...

Sounds like you've had some fun with your car..!

But you have to understand, that I'm not getting rid of my engine for another... I just rebuilt it, and will keep it as long as it is-, or I am -still alive...

[the]

Originally Posted by otto in norway

Alright..
My plan is to make the most of my engine as it is... (NA)
BUT I'm not gonna spend a lot of bucks on an upgrade, that I won't really feel... 1500$ is not cheap!

You sound like you're in the prime Eram demographic. Add in a Cool Collar to keep it together, maybe a K&N filter, and you're good to go.

[RWebb]

I might address the intake before doing SSIs - it is surely easier to bolt on a set of SSIs first tho.

See if Steve Weiner posts -- then your only question is whether you want to pay for it.