exhaust question..
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Junior User
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exhaust question..
Hey guys, im sure its been asked before. But will i hurt my truck a 1987 f150 302 efi 4x4, if i wack off the cats (both are really bad, and original) and the muffler and just run a straight pipe from right in front of where the car are to the existing tail pipe..
The front cat is toatally rusted out.
thanks alot
Jared
The front cat is toatally rusted out.
thanks alot
Jared
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From: Mass.
youll lose a lot of torque, also it will be loud as hell. taking off the cats and mufflers will kill your torque and the truck will be a dog to get moving as the engine has no backpressure with a straight pipe. can probably get away with pulling out the cat but youll have to have some restriction in the exhaust. in most states itll never pass inspection with a complete straight pipe exhaust
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Oh ok thanks, thats what i was wondering I was worried about the back pressure issue and what not..
As far was laws and inspections lol i dont give 2 *****s lol i live in the back woods of hickville minnesota lol
As far was laws and inspections lol i dont give 2 *****s lol i live in the back woods of hickville minnesota lol
Posting Guru
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From: Mass.
as long as you keep the muffler on there or get a cheap turbo muffler of some sort if yours is in bad shape you should be alright. ive replaced a few cat converters with straight pipes and had no issues but still with a muffler. if your cats are really bad and you replace just them with straight pipe you might even gain a little performance but you do need a muffler.
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Ok thanks, your insight is very helpful..
As far as a muffler, would a glasspack work? I have a cherrybomb in the shed i was thinking about using.. I do like the loudness lol i spend all day sitting next to 6" stacks in back of a N14 cummins.. If if ill get worse milage or worse performance ill just get a new muffler like you say..
As far as a muffler, would a glasspack work? I have a cherrybomb in the shed i was thinking about using.. I do like the loudness lol i spend all day sitting next to 6" stacks in back of a N14 cummins.. If if ill get worse milage or worse performance ill just get a new muffler like you say..
Lead Driver
Joined: Nov 2002
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From: Concord, NC
The backpressure thing is mostly misconception. Backpressure and flow restriction are bad -- always bad. Flow velocity is the important variable, which for the most part is determined by flow area or cross section of the pipe. If the pipe size remains constant, removing a stopped up converter should help power and torque across the rev range.
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From: Mass.
its been a proven fact been argued a million times that yes uncorking the exhaust somewhat will help but with complete straight pipe you lose torque but can gain some hp at high rpms (which is useless in a truck). in a truck you need the torque to get the weight moving. But yes if your cat converter is bad replacing it with a straight pipe will probably bring back some and possibly gain hp and tq. as far as the glasspack you could probably get away with it. having complete straight pipe exhaust is only advantageous if the engine is tuned for it (such as in nascar or a lot of drag race cars) on a stock efi motor it doesnt help and in most cases hurts performance
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Postmaster
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The backpressure thing is mostly misconception. Backpressure and flow restriction are bad -- always bad. Flow velocity is the important variable, which for the most part is determined by flow area or cross section of the pipe. If the pipe size remains constant, removing a stopped up converter should help power and torque across the rev range.
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Post Fiend
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From: Almost Heaven
I lost low end torque when I took my muffler off. I did notice a performance gain when I replaced my second cat (the first is supposed to be gutted). These were 200,000 mile cats so I'm sure they were plugged up.
Just my experience.
Just my experience.
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and for drag racing top end horsepower is usually better, it's only when your pulling stumps out of the ground or something like that where you need low end torque
my truck actually picked up 2 tenths at the drag strip when i pulled covers off of the cutouts and jetted the carb up a few jets to compensate but with my 3500 stall converter i basically use top end hp the whole time i am on the throttle
Post Fiend
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From: Almost Heaven
for what your doing you could just run open headers and have no problems, and for the people who say it warps the exhaust valves when you shut the motor off and the valves are hot it's a load of crap between me and all of my friends who run open headers on our drag cars all the time and don't even have exhaust on them i'm sure at least one of us would have warped exhaust valves by now
and for drag racing top end horsepower is usually better, it's only when your pulling stumps out of the ground or something like that where you need low end torque
my truck actually picked up 2 tenths at the drag strip when i pulled covers off of the cutouts and jetted the carb up a few jets to compensate but with my 3500 stall converter i basically use top end hp the whole time i am on the throttle
and for drag racing top end horsepower is usually better, it's only when your pulling stumps out of the ground or something like that where you need low end torque
my truck actually picked up 2 tenths at the drag strip when i pulled covers off of the cutouts and jetted the carb up a few jets to compensate but with my 3500 stall converter i basically use top end hp the whole time i am on the throttle
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