'77 911s exhaust question

cknoll · cknoll's Garage

My 1977 911s has what looks like a ’74 exhaust (the older heat exchangers and no thermal reactors) and no air pump. I initially thought this was the result of aftermarket work, however, I noticed that the Porsche factory emissions sticker on the fan housing mentions no air pump, non-catalyst and that the air pump holes are plugged. Were there '77s that came with the ’74 exhaust? Also, the date stamp on the muffler says 5/77.

Zeke · 03-25-2009, 02:34 PM

What's the first part of your VIN without the last 4 digits? Sounds to me like a ROW (non US) car.

cknoll · cknoll's Garage

So I have to apologize; I wasn’t at home when I made this post. Now that I have looked at it the sticker actually says disconnect aripump tube and plug up. I think this is an instruction for testing and not that the airpump has been disconnected. It doesn’t say anything about a “non-catalyst” on the engine. It says that on the inside of the driver’s door. Both stickers mention USEPA. The VIN is 911720. Thank you for the help.

frankc · 03-25-2009, 07:47 PM

77's were non-catalyst vehicles (notice that there is no restricter in the fuel filler neck), my car has that sticker on the door jamb as well. '78 is when they got cats.

Take a look at your muffler and see if there is a small metal tube coming out near the right side inlet (I assume you have a 2 in 1 out OEM style muffler). If so, I believe this was for the EGR (it's been so long since I disconnected the system I've forgotten), so that may give you some clues to its emissions history if everything else has been removed (thermal reactors, air pump, air pump manifold).

Frank

Zeke · 03-27-2009, 01:07 PM

It's a '77 coupe, first of the 50 state cars with air injection, reactors and EGR. The muffler is a 2 in- 1 out design and looks similar enough to a previous design that you might be able to use it with the non reactor heat exchangers of <'74.

The HE's used with the reactors look similar at first glance to the older ones. The big changes came about in '78 when the exhaust all came down the driver's side thru a cat and into a 1 in- 1 out muffler.

frankc · 03-27-2009, 02:10 PM

Quote:

Originally Posted by milt

The muffler is a 2 in- 1 out design and looks similar enough to a previous design that you might be able to use it with the non reactor heat exchangers of <'74.

Just to verify that yes the '77 muffler does work with the early HEs - I'm using SSIs with my OEM muffler.

Frank