The truth about open headers...
Thread Starter
Launching!
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From: St. Paul, MN
The truth about open headers... I've heard so many different stories about this, I want to hear from you guys that have them how you like it. I've heard that it's bad for the valves and other stuff like that. I'm getting SLP LT's in about two weeks, and was just wanting to put turndowns on the end of them (this should be loud enough, haha, j/k) but not if it will hurt my engine. Can I see pics of your open headers or dual exhaust setups, some sound clips would be nice too!
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From: Troy, AL
Re: The truth about open headers... With open headers and a stock CI engine you will see a pretty large loss of low and midrange power and very little if any gain up top. You'd be better off going through the Y-pipe.
You won't burn your valves but you will need to make sure that you have enough tube behind the O2 sensors so that outside air never touches them. Otherwise your Ltrims will max out positive at idle and you'll run sloppy rich.
Again, for a NA stock CI LS1 engine there is no sense in running open headers.
[ November 25, 2001: Message edited by: Colonel ]</p>
You won't burn your valves but you will need to make sure that you have enough tube behind the O2 sensors so that outside air never touches them. Otherwise your Ltrims will max out positive at idle and you'll run sloppy rich.
Again, for a NA stock CI LS1 engine there is no sense in running open headers.
[ November 25, 2001: Message edited by: Colonel ]</p>
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From: From the Bowels of Hell!!! You want some of me bitch?!?!?!
Re: The truth about open headers... I've run the open header thing at the track and can I tell you, there is NO low end tq. If you want to go with the open headers, do like Colonel says and run a length of collector tube, to keep the outside air from screwing with your O2's. The length of tube is another deal all together. You start off with a long tube, 18" if it will fit, and cut it back. The cheapest/easiest way to determine length is to paint the tube with cheap paint and then make a pass. Cut the tube where the paint stopped burning off. That IS NOT the best way however to get the length right. Best way is on a dyno and run & cut. Run and cut. Run and cut. About 2-3" at a time.
Tim
Tim
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From: Melbourne, FL
Re: The truth about open headers... I can't speak for a stock car on this issue, since mine is not... However, I usually pick up .06-.07 or better and ~1mph or so running open headers over my mufflers. It could also have to do with my crankcase evacuation system, which does not work as well with mufflers on the car. It could be a combined "effort" from the unrestricted exhaust flow, and the crankcase evac. As far as a loss of low end torque, my car 60's as well with or without the mufflers (I do have 12" collectors though), but I have a 4500rpm stall converter also. My car is pretty different than most others out there...
In any case, I'd never run around on the street with the headers open. Besides being obnoxiously loud, it sounds like a dump truck at part throttle/cruise... <img src="images/icons/smile.gif" border="0">
In any case, I'd never run around on the street with the headers open. Besides being obnoxiously loud, it sounds like a dump truck at part throttle/cruise... <img src="images/icons/smile.gif" border="0">
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Thread Starter
Launching!
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From: St. Paul, MN
Re: The truth about open headers... So if I put the SLP's on the the race pipes, then turn downs at the end of those does that sound good? Or should I put race pipes, then y-pipe, then a turn down at the end of that...
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From: Melbourne, FL
Re: The truth about open headers... I don't think open headers are gonna sound "good" on one of our cars, period. Lots of people have different opinions on what sounds good, but I think most would agree that an LS1 through open headers sounds nasty... Maybe I'll try to get a sound clip of my car and post it sometime tomorrow so you can hear it. I have a couple of movies I need to transfer over to .AVI, so I'll try to get links posted here...
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From: Melbourne, FL
Re: The truth about open headers... OK, I've got a video, if I can figure out how to post the link correctly... It's about 1mb in size.
George's Car
George's Car
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From: Troy, AL
Re: The truth about open headers... Let me clarify something....
I meant that open headers on a stock CI LS1 (even with heads and cam) is a bad idea compared to running an OPEN Y-pipe...not compared to running through a full cat-back with a muffler(s).
Now maybe in some stock CI applications a bigger Y-pipe is in order but open headers are not until you get to making some serious power (read: LARGE CI or a power adder.) <img src="images/icons/smile.gif" border="0">
I meant that open headers on a stock CI LS1 (even with heads and cam) is a bad idea compared to running an OPEN Y-pipe...not compared to running through a full cat-back with a muffler(s).
Now maybe in some stock CI applications a bigger Y-pipe is in order but open headers are not until you get to making some serious power (read: LARGE CI or a power adder.) <img src="images/icons/smile.gif" border="0">
On The Tree
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From: Corona
Re: The truth about open headers... [quote]Originally posted by GeorgeC:
<strong>I can't speak for a stock car on this issue, since mine is not... However, I usually pick up .06-.07 or better and ~1mph or so running open headers over my mufflers. It could also have to do with my crankcase evacuation system, which does not work as well with mufflers on the car. </strong><hr></blockquote>
Could the gains be due to weight losses and not more hp?
<strong>I can't speak for a stock car on this issue, since mine is not... However, I usually pick up .06-.07 or better and ~1mph or so running open headers over my mufflers. It could also have to do with my crankcase evacuation system, which does not work as well with mufflers on the car. </strong><hr></blockquote>
Could the gains be due to weight losses and not more hp?
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From: College Station, Tx
Re: The truth about open headers... Open headers ARE worth power. Backpressure is BS - with any properly tuned primary exhaust system (longtube headers certainly fit this bill) you want no restriction after the termination (adding header collector pipes is essentially changing the tuning of the primary exhaust, not affecting back pressure).
So why do people see a loss of power? If you don't change your A/F ratio and timing to work in tandem with the open headers, then you probably will loose power, especially down low. This isn't because of what the headers have done though, this is simply because your car is no longer tuned correctly.
You also may have problems with O2's and long tube headers, as the Oxygen tends to rush back up at low rpm's and cause an overly rich condition - this is another reason why longtubes can sometimes seem "doggy" at low rpm's/low TPS when run wide open.
Now what kind of gain are we talking about? On a stock motor I don't think i will be much more than a cutout, but as your displacement/rpm increases, so does the benefit of open headers.
Chris Bennight
So why do people see a loss of power? If you don't change your A/F ratio and timing to work in tandem with the open headers, then you probably will loose power, especially down low. This isn't because of what the headers have done though, this is simply because your car is no longer tuned correctly.
You also may have problems with O2's and long tube headers, as the Oxygen tends to rush back up at low rpm's and cause an overly rich condition - this is another reason why longtubes can sometimes seem "doggy" at low rpm's/low TPS when run wide open.
Now what kind of gain are we talking about? On a stock motor I don't think i will be much more than a cutout, but as your displacement/rpm increases, so does the benefit of open headers.
Chris Bennight
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From: Troy, AL
Re: The truth about open headers... Try open headers on a stock 346 CI LS1 engine with a mild converter or with an M6. Compare times and traps to the same setup with an open offroad Y-pipe or a cuttout in the intermediate pipe. Assuming correct mixture and timing advance in all cases, I bet your ET and trap speed will not be best with the open headers.
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From: Waxahachie, TEXAS
Re: The truth about open headers... bah... i've never run an ls1 open headers, but I've run my 327 powered thirdgen with them... it SUCKS. You have to set the idle speed really high and as others have said, there is NO low end at all. plus it sounded like ***.
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From: College Station, Tx
Re: The truth about open headers... Why would an engine need backpressure to run correctly though (with a good set of headers?) If you abstract an engine to just a basic 4 stroke cycle backpressure is very bad.
I can give you plenty of examples of open headers on tuned heads+cam cars making the most power and torque. Sure they are moving more air then a stock motor, but it's not a night/day difference. If it helps on this motor then it is not going to *hurt* on a milder version. How much gain you see may be questionable, but not a loss.
Backpressure is th enemy - anything that reduces it is good.
Chris
I can give you plenty of examples of open headers on tuned heads+cam cars making the most power and torque. Sure they are moving more air then a stock motor, but it's not a night/day difference. If it helps on this motor then it is not going to *hurt* on a milder version. How much gain you see may be questionable, but not a loss.
Backpressure is th enemy - anything that reduces it is good.
Chris
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From: Melbourne, FL
Re: The truth about open headers... [quote]Originally posted by SCZ28:
<strong>
Could the gains be due to weight losses and not more hp?</strong><hr></blockquote>
Not in my case... My two mufflers weigh in at about 10-15lbs for the pair...
<strong>
Could the gains be due to weight losses and not more hp?</strong><hr></blockquote>
Not in my case... My two mufflers weigh in at about 10-15lbs for the pair...