So.... I see that the rear exit plumbing on the 1.7/1.8 SSI exchanger model does an "S-Curve" in the upward direction...… making it impossible to attach a stock 2.0 muffler.

The 2.0 SSI exchangers have more of a STRAIGHT design to the exit flanges.

Question: Other than the shape of the exit flanges, is there any difference in the internals of the two designs? Does the 2.0 have larger diameter tubing? Better flow?? Or is the only difference the rear flange design?

I just realized that I have 1.7/1.8 SSI exchangers on my 2056 motor..... I realized this when I attempted to attach my (new to me) stock 2.0 muffler

Looking to learn before I start removing/swapping/customizing/ruining

Same ID/OD so they flow the same. Just different in the exit direction. and need a different hanger and muffler.

The less bends the better in terms of airflow.
But I bet not even a dyno would be able to tell the difference in airflow between the 1.7 and 2.0.

Zach

Height of the inlets and flange spacing are the biggest difference

Check the classifieds Someone has a WTB for a 2.0 muffler.

Then you can start looking for a 1.7/1,8 muffler to match your SSI HE

You will also need the 1.7/1.8 bracket, if you don't already have that part.

And the correct HE to muffler gaskets. 2.0 style vs 1.7/1.8.

As mentioned above the real difference is in the pipe exit at the rear.
Which equates to a different hanger and muffler.
This may help.

Click to view attachment

Good measurements, how about the 75/76 cars, any numbers there ?

The only numbers that matter for the 75/76, are the horse power numbers that drop cause of the exhaust.

use what you have.