Y pipe to Manifold
<HR style="BACKGROUND-COLOR: #ffffff; COLOR: #ffffff" SIZE=1 sizcache="1" sizset="27"><!-- / icon and title --><!-- message -->Was wondering if when replacing the stock "Y" pipe at 2 1/4" and going with a 2 1/2" new "Y" pipe will this bolt directly on the stock 5.0L exhaust manifolds??? or is something else needed to be done.

Also how necessary is it to run cat, as we no longer need to smog after a certain age?? will it through a light indicating a problem?
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what truck is this going on? I think older then 78 is usually excempt for cats, but you would be better off running a cat. Cleaner air and better smell. You should be fine on the Y-pipe, its the 351w that has the odd 2.25 and 2.5 manifold flanges.

Are you looking at fabricating a pipe or buying a pipe?

Unless your truck is a 96 year or OBD2 you won't through a light without a cat.

 

It is going on my 1986 Bronco with 5.0L and have been told that the 86 has a 2.25" exhaust from front to rear. And yes I am looking at a Y that is allready made.

 

Magnaflow makes a bolt on kit for the 5.0.

 

Regardless of the age (model year) of the vehicle, if its OEM equipment includes a functioning catalytic converter it cannot be removed under any circumstance save ONE... the device must be malfunctioning in some way. (which includes, but is not limited to, clogs, burst seams, dislodged substrate).

Given the age of the truck in question, if the cat has indeed failed, it may need to be replaced. Depending upon local/state law, the failed unit may be removed and no replacement installed so long as the vehicle's exhaust system is complete under the limitations of those local/state laws which govern the model year vehicle in question.

Sorry for the rather formal response but its about as succinct as I can make it that way.

As for pipe diameter, as long as you don't exceed about 3" diameter for the main pipe of a single-pipe system with the 302 you should be fine.