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Dual exhaust

I love my Chevy Chevette!
Posts: 1
Joined: 04/14
Posted: 04/06/14 06:02 PM

Hi Guys I am new here and I have a question I hope someone can answer.My question is,is how do you convert a single catalytic converter exhaust system in to a dual catalytic exhaust system when you have one oxygen sensor hook-up?Can you add another one and combine the two without screwing up the signal to the computer or is there a way to to this and keep the car emissions legal?By the way,mine is a 1985 Pontiac t-tops Trans Am 305 TPI automatic with a WS6 package and Aussie 9bolt positraction.It needs some body work(bumbs and bruises here and there,it seems to run great,but haven't had it on the road since I bought it,needs new tires.Car was due for the scrap yard until I got my hands on it,originally was gonna use the drivetrian for my 1984 Camaro until I saw all the factory goodies and decided to preserve it.Hope ye'all can help out help me out here,it would greatly appreciated. Smile  

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V-6 Camaros rule!
Posts: 36
Joined: 10/13
Posted: 04/06/14 07:52 PM

before you go any farther...

does the engine run???


is the car sitting on its tires.???  turn the key to the RUN position.. and have a friend rock the steering wheel back and forth several inches..

you will have the hood open and be watching the steering box..  i am hoping that the steering box mounting area and frame horn is NOT  damaged like so many other 3rd gen cars..  there are bars that bolt across the sway bar frame bracket mounts that really firm up the steering..   make sure that the triangular braces from the bottom of the frame horns to the crossmember are properly installed.. bolts tight.. they are self tapping so don't use an impact to check them..

while you are looking under the car.. make sure it has a rigid air dam bolted to the bottom of the radiator core support.. this is usually something like a HDPE plastic version.. with 5 or 6 small bolts into J nuts..  without this the 85 models will overheat at any speed over 53 MPH..  it was only a 40 buck part at GM.. i don't know if they are still available..

why do i know all this.. my sister had an 85TA.. and i have had a bunch of other early 3 gen cars that were owned by friends and customers..

as for your question..   with a 305 Vin F TPI motor.. you will find the exhaust is huge already..

if you want to go bigger. and a dual cat...

walker # 16101   89 to 92  camaro and trans am's  with 305 and 350s with dual cats..  if you could find either this 300 buck part... or a used one to duplicate the head pipes.. you could create a dual exhaust.. is there room under the middle of the car for it???  see whats available online from summit or other vendors.

20200025 Wal 16101 Pri Larg

46744 is the single mid pipe back to the dual outlet muffler #22354

you can get in some areas..  high flow converters installed.. but please.. make sure they spend the extra time and install them so they are removable with a ball type flange on the back of the converter.. this allows you to drop the Y pipe and converter without needing to drop the mid pipe and muffler.. thats usually a hard part to remove..

putting dual exhaust on a 305 even a TPI 305 is almost a waste of money.. the factory system works really well..  unless you are going drag racing or something like that..

the oxygen sensor should be on one of the exhaust manifolds..

if you live in an area where there is smog testing.. don't modify it..

if you have more questions.. i am always around..  

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