'81 ROW SC Backdate Question
 

Finally ready to replace the original factory exhaust system, and after exhaustive research I still don't have clarity as to whether an SSI backdate (2 in/1 out) is the way to go. Yes, I understand the SSI appeal with regard to build quality and resale value, but I'm wondering whether the claimed HP/torque increase would be as significant in a ROW car given the already higher compression and increased HP?

Would OE-style stainless HEs with crossover and a Dansk Euro pre-muffler and sport muffler (in a ROW car) come close to a backdated system in terms of performance?

Looking for a technically-honest assessment. Will I FEEL the difference between these two approaches?

Also want to add that I'm generally a purist, but for my 911 I'm willing to tastefully deviate from stock...

Thanks!

I'm right up the road from you in Haworth. I've got a '79 SC that I've swapped to a backdated exhaust, using factory early 911 (70-74) steel heat exchangers I had left over from a car I put SSI's on...so I cleaned up the heat exchangers and bolted them on my big port '79 3.0, with an M&K 2 in-2 out muffler, it transformed the car, much better throttle response, much happier at high rpms.

I'd offer you a test-drive but I drove the car out to California last year, and won't be bringing it home until late may.

The biggest change from the stock exhaust to the earlier style is in the midrange, not the peak horsepower number. Yes, you will feel the difference. Which muffler you choose to use will have an impact, too. There are a lot of them out there and few of them have any real tuning/development behind their design. In that respect, you might choose to use something that has been tested on a dyno, so you at least have some idea of whether the muffler helps or hurts.

My personal preference is for the Monty mufflers. I also prefer the 2-in, 2-out version but that choice may not suit you.

The engine in my 1979 ROW SC was inadvertantly built into quite the 3L hot rod by the previous owner. When it was time to rebuild, he picked up a set of pistons and cylinders from a low mile '81 ROW SC, had them reconditioned, cleaned up the stock big port, big valve heads, and added 964 cams.

About 2 years ago, I upgraded the exhaust with a set of SSI's and a Dansk 2in/1out muffler. The difference in performance was noticeable immediately. There used to be a noticeable step up in power at about 3.5k and the car felt a little winded above 5.5k. Now it pulls hard from idle to redline. The CIS is definitely choking the engine now.

When I added SSI's to my 79 SC, it certainly sounded faster.

Thanks all, for the input. Seems like even a ROW car would noticeably benefit from a backdated system...

Muffler choice is difficult because I'd like to keep the rear fog light, and any tail pipe with an exit angle other than OE will melt the light housing. Found this out after mounting a Dansk sport muffler...

Since the fog light is an added-on part, maybe fabricating a new mounting bracket and moving it a little bit would help.

The hard part of picking a muffler is finding any objective info on it. Bruce Anderson's book had some suggestions. Steve Wong has dyno-tested a bunch of cars and might have some general ideas. I'd try to avoid the "this is what I bought but I've never actually tested it" sorts of suggestions. Around here, price seems to be a pretty important factor in muffler selection; more so than any other factor.

Good luck to you,
JR

You could always get a rally muffler with 3 tips. That way you can cap the side when you want sport and cap the centers when you want quiet. Plus it would clear your fog light to boot.

I have SSI's on my '83 ROW with a Dansk 2/1 out and that is a nice set up.
Being a row engine doesn't make much of a difference over the US model as both have strangled exhaust systems to an extent.
SSI's are nothing more than an upgraded (stainless) rendition of the early Porsche factory pre emissions exhaust.

I did early heat exchangers and Bursch on my low comp '80 RoW (big port, advanced cams) and noticed a significant power increase in the low and mid ranges, and only a slight increase in the upper range. I believe this is indicative of the cam timing.

Your '81 930/10 with higher comp and retarded cam timing will likely benefit in the mid and upper rpm ranges with a slight increase in the lower.

It's definetely worth doing.

As far as purity goes, SSI heat exchangers are on the good list for upgrades, IMHO. Im more concerned about the sound. With that in mind, i think SSIs with a SS sport muffler, 2 in 1 out, sounds very very good. And, it fits. Im sure it will be a good upgrade over the stock setup...plus it adds a coolness factor. I bet the MK muffler guys have dyno results and ive seen others such as triad posting baseline dyno results.

Very helpful guys, thanks! One other thing I'm not clear about—what, if anything, do I have to do to the heating system assuming SSIs and an M&K 2/1 muffler?

Original heat system ducting should bolt right up. You can backdate if you like as well.

Not much, just reroute some flex tubing.
You will need to add an oil re route pipe though for the SSI's.

Well...if you are going to backdate the exhaust,you might as well backdate the heat for a complete look :) .