Question on 2.5" stock downpipe fitment...

[V6-Sauce]

I have to remove my stock cat convertor. It's very clogged. Anyways right now intil I get another Cat I'm going to use the test pipe that came with my hooker catback. Question, I have to cut the bottom part of the stock downpipe and enjoy a 20 or 45 degree bend and connect to testpipe opening. Is the stock 2.5" downpipe coming down towards the cat is it 2.5"Inner Diameter or OD?

 

[turbofabricator]

Remove the cat, take a big pry bar and knock,all the guts out of it. Then install the shell and never ........ever replace it. With a good tune, it will pass ANY sniffer test in the country. This will be the cheapest 30 horsepower you ever gained.

 

[V6-Sauce]

thx, yeah I was thinking that after gutting the cat to try to stick the test pipe through the old cat and weld it up so it looks stock and also give's the exhaust that smooth straight pipe flow.

 

[earlbrown]

It'll go turbulent when it hits the oval exit flange. Putting the pipe inside the gutted cat will just be more work, and slightly shrink the I.D. a little bit.

 

[monteperformanc]

You shouldn't need to cut the downpipe to remove it. I have the hooker test pipe. The cat was stuck on the downpipe. I just cut the cat off, and then sliced the remainder of the collar that was stuck on the downpipe. Downpipe was untouched. If I have a pic I will post it.

 

[monteperformanc]

I cut along the red lines. First vertical with a sawzall, then the horizontal cut with a cutoff wheel. Then the test pipe went right on with a clamp.

 

[earlbrown]

Just jack the car up a little higher than normal. The DP and cat can come out in one piece.

 

[1KWIKSIX]

Here's an interesting replacement. Just have a muffler shop weld on your 4" flange which is taken off your old catalytic convertor & Bob's your Uncle......you'll be good to go!