911SC Exhaust Backdate Questions

[schleven]

My stock heat exchangers and exhaust on my 1981 US 911SC are rusted and shot. I'd like to back-date the system but have heard several different things regarding flange size, exhaust compatibility, etc.

First question: Which older heat exchangers/headers will be compatible? For example, will a set from a 1972 911T work with my car? (I know it needs to be pre-75 but how far back can I go?)

Second Question: If I were to go with SSIs, do I need thin flange or thick flange? I've seen both recommended for my year of car.

Thanks in advance.

S

[euro911sc]

When mine were shot I simply cut off the heater boxes for that 'factory' header look Running temps dropped noticeably. After a while I went full headers with a 2in 2 out. If you do not need the heat then I would recommend headers instead of SSIs or similar. I would not go back to pre-75 setups as I believe that the diameters are too narrow for optimal flow out of your 3.0. This leaves SSI's or other aftermarket systems as your options. Also, do not forget that you will need a different oil line to avoid your new exhaust system.

As for flanges, I believe the US cars need the thin flanges. You can look at your current setup and if the flange is 3/8" it is thin. If you post a pic we should be able to tell.

[shipfaced]

Look at backdating to a '74 set-up. Plenty of kits available. Mine is an SSI on an '80 SC with a Bursch 2-in-1-out muffler. Supposedly adds 15% more HP and torque. Good raspy cackle sound as well.

[Josh D]

Originally Posted by euro911sc

I would not go back to pre-75 setups as I believe that the diameters are too narrow for optimal flow out of your 3.0.

Actually both the early heat exchangers ('74 and earlier) and the SSI's have 35MM primaries and work equally well on a 3.0. SSI's just last longer and look better.

[Josh D]

Originally Posted by shipfaced

Supposedly adds 15% more HP and torque.

More like 15 hp total, not 15%, which would be 27 hp.

[shipfaced]

Just repeating what the advertising fluff said on the 15% HP and torque gains. Feels stronger than standard, but never put a dyno to confirm.