Yet another exhaust question..... - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-07-2005, 10:49 PM
yeko
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Yet another exhaust question.....

Iíve gone over most of the posts about exhaust and the more I read the more confused I get. It seems to be the general consensus that you must have back pressure to retain your low end torque. If thatís the case, why would you want to add headers and a free flow exhaust system when you would ultimately have to restrict the flow to get that back pressure? Could someone explain this in a way that even an old country boy can understand?

Iíve also heard that the back pressure thing is not an issue for the older trucks (mine is a 91, 2500 with a 350). What brought all this up is that my cat went bad and I just had the muffler shop cut it out and add a pipe.

Thanks
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post #2 of (permalink) Old 04-07-2005, 11:16 PM
K5Blazerman77
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Re: Yet another exhaust question.....

if you have too little back pressure it can cause problems like burning of your valves, but just cutting off your cat. and still having a muffler wont cause that, its enough back pressure
post #3 of (permalink) Old 04-08-2005, 07:58 PM
cedjunior
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Re: Yet another exhaust question.....

Back Pressure = bad. If you want back pressure stuff a potato in your tail pipe.

Its not backpressure you want. Its velocity and exhaust scavenging. If an exhaust pipe is too big, whether its a header primary or a y-pipe or cat-back exhaust piping, the exhaust gases flowing through that pipe will lose velocity. Think of it like this, if you had a drinking straw and a cardboard tube from a roll of papertowels, and blew through both of them, you'd notice the air comming out of the straw felt a lot faster than the air coming out of the cardboard tube.
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post #4 of (permalink) Old 04-08-2005, 09:57 PM
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Re: Yet another exhaust question.....

With a 350, you want a single 3" exhaust all the way out. Or you can go for a dual no bigger than 2.5".
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post #5 of (permalink) Old 04-09-2005, 07:50 AM
MSF
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Re: Yet another exhaust question.....

[img]/ubbthreads/images/graemlins/RockOn.gif[/img] Yeah, what she said.
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