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a good exhaust might even pick it up a bit..
...Phill
My Duster had the same headers with a three inch pipes feeding to a set of Magnaflow 3.0x14 long oval muffs mounted at the rear bumper and the car only pick up .04 ET and about a 1/4 MPH increase in the 1/8 mile, probally due to the weight removal 
I haven't tried removing the exhaust at a 1/4 mie track yet on the Duster
Ron
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Last saturday picked up almost two tenths.
10.32-34 to 10.14. Also picked up 1.75 mph.
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Last saturday picked up almost two tenths.
10.32-34 to 10.14. Also picked up 1.75 mph.
IMO this is about right for a full street exhaust of ANY BRAND. Anyone who does not pick up significantly is probably in need of collector extensions and/or jetting/timing changes or just isn't moving a lot of exhaust-aka not making a lot of power.
Just like swapping intake manifolds, cams, headers, etc., it depends on the overall package and carb tune-up. A single different part can alter jetting requirements, so only re-tuning & testing to know the best tune-up for each will provide the best comparison between the part changes. 
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Thanks for all the info. I guess with what im reading is my car is about average for exhaust vs no exhaust. Plus a real slippery track. No more exhaust for me at the track
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My Scamp with a 360,slowed down almost two tenths without the muffs. I installed extensions, but I didn't jet up the carb.
How much more jet do you need with open exhaust?
Dennis Jokela
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Thanks for all the info. I guess with what im reading is my car is about average for exhaust vs no exhaust. Plus a real slippery track. No more exhaust for me at the track
Its all about the back pressure in the exhaust, every
bend and which muffs. Some that are saying they picked
up is more than likely the front pipe is helping
the collector being a extension... a off the shelf
header MOST times has a collector thats way too short
so the pipe helps that(of course with a little to
no back pressure muff)
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IMO this is about right for a full street exhaust of ANY BRAND. Anyone who does not pick up significantly is probably in need of collector extensions and/or jetting/timing changes or just isn't moving a lot of exhaust-aka not making a lot of power.
Quote:4 inch collector into 4 inch s/s pipe out to the bumper
For me,it's not worth the effort involved to remove the exhaust system.I would pick up just with the weight savings
Quote:Quote:4 inch collector into 4 inch s/s pipe out to the bumper
For me,it's not worth the effort involved to remove the exhaust system.I would pick up just with the weight savings
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Exactly, Mike. Kind of what I said. Some exhaust systems may bandaid a poorly designed/tuned exhaust(primary pipe too big/short-collector too big/short ect). Locomotion, I know you know what's what so I don't have an answer for you. I do know that for classes(non bracket) that don't require an exhaust very seldom is one ever used.
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Exactly, Mike. Kind of what I said. Some exhaust systems may bandaid a poorly designed/tuned exhaust(primary pipe too big/short-collector too big/short ect). Locomotion, I know you know what's what so I don't have an answer for you. I do know that for classes(non bracket) that don't require an exhaust very seldom is one ever used.
Just theorizing, but considering all the restrictions we have, including no porting, stock lift, compression & valve sizes, I am thinking that the X-pipe helps scavenging and increased the velocity through the entire engine. As mentioned, when I leaned the carb a bit, it ran better! (Stronger signal to the carb?) The 3" pipes and efficient, straight through mufflers are probably not a restriction for my engine size and rpms. So it helped my combo, in particular, to run better.
But over the years, I have heard of some pretty fast muffled cars. Although some did have what were arguably called "mufflers".
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IMO this is about right for a full street exhaust of ANY BRAND. Anyone who does not pick up significantly is probably in need of collector extensions and/or jetting/timing changes or just isn't moving a lot of exhaust-aka not making a lot of power.
So you're telling me that a muffled street car should drop 2 tenths just by dropping the exhaust no matter what kind of exhaust system they run?
I tried 2 different lengths of collector extensions and tried re-jetting up and down and timing and could not get the car to run quicker with open headers, that made me very happy so the exhaust never had to be dropped again.
You might be right that the headers may not be perfect but who's gonna try a bunch of different headers to try and beat the times you turned with your exhaust system. And at 134-136 MPH I think that's decent power for a street car.
I think a good exhaust system will not slow a car down.
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Are you using step headers and a merge collector?
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I have noticed little to no gain with my 3" exhaust uncapped or running it all the way out back..11.0's either way..
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I have noticed little to no gain with my 3" exhaust uncapped or running it all the way out back..11.0's either way..
thats just because youre awesome
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Myron,
Do you tune your stocker with an air/fuel ratio gauge? If so, what kind of ratio do you tune for at wot?
Jeff
Never had the engine or the car on a dyno either. Despite doing well, I don't have the time or budget to do as much as I'd like to.