My 86 trans am has a 305 v8 tpi. All the auto stores and garages say the car is supposed to have 2 1/2 inch piping or sometihng around that.


My car has 3 inch piping very big tubes and i'm wondring why?

im the 3rd owner and i keep getting told someone added those afterwards.

this would also mean they would of had to replace my manifolds.

the manifolds look original. cast iron and surface rust. and they have all the air pipes coming out to work with the factory setup.

so what did they do take bigger manifolds and pipes from a later year?

all the piping looks correct for our cars just thicker piping.

as far as i know i have a 305 did 350s come with bigger exhaust pipes?

it would be great iff i ended up having a 350 engine but i know the car originally had a 305 and as far as i know still does. but like i said the exhaust size is puzzling me.

the garage had to order special parts because when they ordered what is supposed to go with my year and engine the pipes are smaller.

 

Check post #4 of the following link:

https://www.thirdgen.org/forums/exha...-question.html

JamesC

 

The size of the pipes, doesn't mean they had to change the manifolds. Whether the pipes are 2" or 20" (insert sarcasm here).....The manifolds could have remained.

A previous owner just changed them out at some point. Nothing to be concerned about in any way.

 

thanks for all your info guys.

it was a big help. yea i guess teh manifolds could be original.

was just a pain because i wasnt replacing everything at once.

so i had to find a cat converter a y-pipe etc.. at individual times and the garages ended up finding 3inch piping that matched the rusted out ones that someone put in.

its not a bad thing performance wise but is hard to find the parts because i dont know what to ask for because my spefic year doesnt have the right size in the books.


everything is fine for now but i tihnk im going to get a little creative and take it to a special exhaust shop later down the road. i took my last emissions test last month so whenever that cat converter goes its all getting updated.

 

have you thought of buying a magnaflow cat back? Here's a link. It is a 3 inch system and is very nice and clean. Mine is not hooked up just yet, still trying to get find the right hangers. In any case...have fun
http://www.magnaflowstop.com/product/16829

 

the cat back is a nice system. my only concern is where the cat converter is there is alittle neck coming out to bring exhaust fumes to thin metal pipe that goes back up into the engine area.

wat is it for and what do i do with it if i ever do a cat back system?

 

Emissions. Leave it.

JamesC

 

i want to leave it. but does the cat back system have that little arm that sticks out that the air pipe can be connected to?

 

The cat back is the system behind the cat (thus cat 'back'), so if you leave the cat, the piece in question will still be there.

JamesC

 

The tube you are referring to, works in the opposite direction.

The smog pump on the engine, pumps clean air into the catalytic converter, through that tube, to feed oxygen to it, to help it increase in its burning efficiency in reducing smog levels.

There is no legal way to remove it.

However.....Running a good cat that is made to function correctly without the air tube, can (& will) clean up the tailpipe results very well. When I got my GTA, the smog pump was gone. BUT it had a later model style, aftermarket converter that doesn't need that tube.

Technically my car is illegal & should not pass the visual portion of the inspection. However, since the results have always been way better than when the car was brand new off the lot, the inspectors have "ignored" the wrong cat. They coulda failed me purely on visual, but I also woulda fought it big time, proving that my car runs very clean, despite what the books say I should have. That is what the Referee Inspector Process are for.