Exhaust Question?

[TheBocSez]

Would there be a problem going with a 2.5 mid pipe into a 2.25 inch mufflers and tailpipe? The car is in my sig and is a street car with very few track trips. I already have aftermarket mufflers that are 2.25, so I was just thinking about replacing the mid-pipe. I plan on replacing the stock headers with aftermarket 1.5 units, since its an AOD vert, I understand that a little added back pressure will assist with the low end torque.

Future engine mods include a Tmoss ported lower, Thumper Heads, 1.7 rr and a 65mm TB. Havent decided on a cam change for sure but if I do, it will be the Crower 15511. Just providing this info incase it influences the outcome of the exhaust question.

I remember a few years ago in hot rod or carcraft mag. there was a guy with a BB Nova, that ran 3" mid pipe into a 2.5 cat back, his theroy was that the exhaust gas cooled as it traveled the mid pipe and that the smaller cat back helped with keeping the gas velocity high? Does that make any sense?

Thanks for the help.

 

[Sir Hacksalot]

in the last Hot Rod, they did a test on a 2.5" and 3" full exhaust system on a big block chevy, and the 3" made more power the entire way through.

Hax

 

[rick237]

what mufflers are you using??? You should just go with MAC PRO DUMPS because anything else just isnt good ..... the dumps sound so good they dont have that constant low rumble that just gives you a headache and the dumps flow sooooo much better than (sorry guys with flows) those shotty flowmasters that everyone raves about so anyways what muff are you goignt o be running???

 

[TheBocSez]

Plan on running Dynomax Super Turbos. Getting old and need a more quite exhaust. Had them on my GT350 and liked them, I know there are probably others that make more power but as you can see by my future parts list, Im not trying to build a track terror or a street terror for that matter, just a nice ride with some more umphh.

 

[tmoss]

The exhaust gas does cool as it exits through the pipes, but that is why you want the same or larger pipe the further back you go. Open headers are like having an infinatley bigger exhaust pipe, but that is not optimal as you have seen that adding some back pressure does add power in many cases. but small catback pipes are not the way to go. It won't hurt a ton to run it that way for a while though. Guys with p[lenty of bucks will Jet-Hot coat the entire exhaust system to hold the heat in. Back in the day when ZZ Top built Cadzilla, they wrapped the entire exhaust system from the headers back with Thermo-Tech ceramic fiber wrap. I had it on my 67 Camaro headers.