identifying stock 76 heat exchanger

[mike76911]

I have a 76 911 S. How can I tell if it has the stock heat exchanger or the earlier 74 type ? It has a crossover pipe,
both sides go into one pre muffler then into a muffler with one inlet and one outlet.
Thanks for any help.

[pa911]

sounds like it's stock,74 had no crossover pipe that i know of.muffler would be two in.

[Jim Sims]

The below thread has an image of original OEM 76S HE's and three to ones in place of the thermal reactors.

SSI's onto a '76S step 2

[Joe Bob]

Depending on the area of delivery or mods by previous owners there are not many differences between 74 and 76 exhaust.

73 and earlier had equal length HEs with a dual in muffler.

In CA, the exhausts started using thermal reactors in the mid 70s, then cats...most necked down the the three cylinders on each side to a single pipe, then to a cat that fed a single in muffler.

Depending on the smog rules, early HEs or aftermarket SSIs were substituted to get the motor to perform better....

[Rex Walter]

mike76911

I wondered the same thing about my 75 for years. I could never find a good picture that showed what thermal reactors looked like or what a 74 looked like. My stock exhaust does not have thermal reactors. The exhaust exits toward the front of the car on each side, goes into a crossover pipe in front of the engine, then into a pre-muffler that runs to the back of the car, then into a single in, single out muffler.

Here is a 74 that exits to the rear, for a double in muffler (no cross over - no pre-muffler):
http://www.pelicanparts.com/catalog/images/exhaust/1-8-2.jpg

Here is a picture of my 75:
http://www.pelicanparts.com/catalog/images/exhaust/1-8-1-18.jpg

And here is one with reactors:
http://www.pelicanparts.com/catalog/images/exhaust/1-8-2-10.jpg

Best of Luck - Rex

[Maltese Falcon]

Per your description, you have the 49 state (federalized) pre-muffler style. The Cali. 1976 would have had the thermal reactors style HBs. This federalized style also went on in 1978 with the introduction of the 3.0 SC, and got the cat convertor stuffed in place of the pre-muffler. The 49 state style is a power robber-best upgrade to SSI's or headers (if you don't need heat)
Marty