Back Dating 3.0 CIS Exhaust

[Swank911]

I have read several things that suggest back dating the exhaust on CIS engines. What is the advantage of this?

How far back should I go, I have a euro 3.0. Should I put 2.7 heat exchangers on? Can I use the 2.4 SSIs that I have?

Thanks for the help.

Jon

[marcesq]

The advantage is more power and smoother power curve because the SSIs are true equal length headers with heat for the cabin.

The only variables are flange thickness requireing change of exhaust studs, and port size. The latter you will not know for sure until you pull one of the existing heat exhangers.

One other problem might be the O2 sensor. If your car has one the '74 SSI will not have the bung hole for it.

Oem '77 heat exhangers will not help as they are not equal length and not made of SS.

Search for SSI on this board and you will find posts with pictures. Also check the tech articles on this subject and you will find more pictures.

My 1 cent.

[RarlyL8]

You need to backdate to a pre-73 style exhaust with a 2-in muffler.
SSIs are the most popular but stock units will work as well for less money.
Look for a noticable butt dyno gain.

[Swank911]

When you say Pre-73 do you mean Pre-73.5 CIS?

I currently have a pair of 73 SSI headers from my 2.4E with MFI.

[Chuck Moreland]

Actually the early style heat exchangers were equipped up to and including '74. You can find these used usually for $150 - $300 depending on condition. Find a good set, they rust! You can add an O2 sensor if you need one.

SSI is also a great option as mentioned.

Don't worry about port size. The tube diameter is the same for all years, 1.5 inch. Do stay away from SSIs made for the 3.2, they do have a different port shape. Otherwise you should be okay.

You may need to change studs, depending on what length you have now.

This is a great upgrade (backgrade?). You will feel a definite increase in power and the engine will run cooler.

You will need to get a two-in muffler to connect to it.

[Superman]

Yes, the '73 SSI units are the kind of thing you need. I am in the middle of this upgrade myself, using '73 HE and muffler. I am not convinced that shorter exhaust studs are necessary. The ones with the barrel nuts will have enough clearance, and I suspect the other ones will too. If not, you can just cut them down. I am told the tail pipe is not located in the correct position, but in test fitting, I find that the tail pipe is almost in the perfect position. Just a little bending needed.

The biggest problem to solve is the oil line. That hard oil lind across the front of the engine (pulley-side, toward the back of the car) is right in the way. There is a replacement oil line you likely will need.

I am told the modern, new SSIs have bigger ports and tubes that work better with 3+ liter engines, but I know for certain that the early, smaller units work very well.

[Swank911]

Excellent. Thank you. I have the SSI Headers for the '73 so I will go with those.

As for the Mufflers, any I should definetly stay away from?

Definely two in, two out!!

Jon

[marcesq]

Hey Jon:

Here is my preference:

[Swank911]

That muffler is what came with my car when I bought it. They sound awsome with the 2.4L.

Who make that muffler? My current one is rotting out.

Jon

[marcesq]

Jon:

Pelican sell the monza which is what I have. I believe that Ansa makes a similar model.

Check here:

http://www.pelicanparts.com/catalog/shopcart/911M/por_911M_exhaus_main.htm

Have fun.