can i run open headers
Burning Brakes
Joined: Apr 2007
Posts: 1,028
Likes: 1
From: SOUTH ELGIN IL
if you have the side tubes on you shouldn't "blow anything up". However, you might suck in a bird when you let off the gas. If you aren't running at the track at WOT I'm not sure why you would want to do run this way. Backpressure is important for a number of reasons.
You will also get a noise ticket in about 40 seconds with a well built 383 and open exhaust- speaking from experience on this one
You will also get a noise ticket in about 40 seconds with a well built 383 and open exhaust- speaking from experience on this one
Team Owner
Joined: Feb 1999
Posts: 34,453
Likes: 665
From: Republic of Texas
you asked the same question here, not sure if you saw some of the replies. 
http://forums.corvetteforum.com/c3-g...e-options.html
http://forums.corvetteforum.com/c3-g...e-options.html
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Never considered backpressure as being an engine's friend, but that's another topic. In any event, with open headers the pressure you'll receive from your neighbors and the authorities will be your problem. Heck, some tracks and sanctioning bodies even have noise limitations...
Race Director
Joined: Apr 2000
Posts: 17,671
Likes: 199
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
if you have the side tubes on you shouldn't "blow anything up". However, you might suck in a bird when you let off the gas. If you aren't running at the track at WOT I'm not sure why you would want to do run this way. Backpressure is important for a number of reasons.
You will also get a noise ticket in about 40 seconds with a well built 383 and open exhaust- speaking from experience on this one
You will also get a noise ticket in about 40 seconds with a well built 383 and open exhaust- speaking from experience on this one
Thread Starter
Racer
Joined: Aug 2010
Posts: 263
Likes: 0
From: bethpage NY
you asked the same question here, not sure if you saw some of the replies.
http://forums.corvetteforum.com/c3-g...e-options.html
http://forums.corvetteforum.com/c3-g...e-options.html
Thread Starter
Racer
Joined: Aug 2010
Posts: 263
Likes: 0
From: bethpage NY
well im 22 and this is my first real build like this and im doing it all myself (except the machining) and im just trying to see what all my options are i know its a small item and there are other things im more worried about like trying to set this 700r4 but it was on my mind so i figured id post thanks for all the advice guys this forum has alot of really helpful info for someone like me
Drifting
Joined: Jul 2006
Posts: 1,871
Likes: 6
From: Sault Ste. Marie Ontario
The cops may not take to kindly to a 22 year old running around in a Hot Rod Corvette with open pipes!
I run 2.5" Sweat Thunders in my pipes (LOUD). If I see a cop, I generally get the car into 4th and slide by them with my foot off the throttle.
At 50, I worry about the cops I can't see that may be watching or listening to me run through the gears.
You may what to rethink open headers if you ever what to sneak home some night.
I run 2.5" Sweat Thunders in my pipes (LOUD). If I see a cop, I generally get the car into 4th and slide by them with my foot off the throttle.
At 50, I worry about the cops I can't see that may be watching or listening to me run through the gears.
You may what to rethink open headers if you ever what to sneak home some night.
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Race Director
Joined: Apr 2000
Posts: 17,671
Likes: 199
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
The cops may not take to kindly to a 22 year old running around in a Hot Rod Corvette with open pipes!
I run 2.5" Sweat Thunders in my pipes (LOUD). If I see a cop, I generally get the car into 4th and slide by them with my foot off the throttle.
At 50, I worry about the cops I can't see that may be watching or listening to me run through the gears.
You may what to rethink open headers if you ever what to sneak home some night.
I run 2.5" Sweat Thunders in my pipes (LOUD). If I see a cop, I generally get the car into 4th and slide by them with my foot off the throttle.
At 50, I worry about the cops I can't see that may be watching or listening to me run through the gears.
You may what to rethink open headers if you ever what to sneak home some night.
Race Director
Joined: Apr 2000
Posts: 17,671
Likes: 199
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Sorry but being the CF's self appointed myth buster I'd like to hear it too, I don't see too much in place on a Top Fuel Dragster to create any back-pressure to get it to go much faster.I am not trying to be a smart-*** here or anything like that but in the 10 years I have been here I have seen many old wives tales overturned so much so that they are never even mentioned anymore. This one still lives on
Melting Slicks
Joined: Oct 2005
Posts: 2,056
Likes: 8
From: Redruth Cornwall
Sorry but being the CF's self appointed myth buster I'd like to hear it too, I don't see too much in place on a Top Fuel Dragster to create any back-pressure to get it to go much faster.I am not trying to be a smart-*** here or anything like that but in the 10 years I have been here I have seen many old wives tales overturned so much so that they are never even mentioned anymore. This one still lives on
http://www.uucmotorwerks.com/html_pr...torquemyth.htm
Having said that there are similar posts saying why back pressure is good! lol.
Would like to know the truth.
Race Director
Joined: Apr 2000
Posts: 17,671
Likes: 199
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I have read allot of theory etc etc. In some guys car who is using french fry grease for fuel back-pressure might help him. Tell a F1 driver you are going to put something on his exhaust that will make it harder for the motor to expell the the burnt gasses an take a good look at his face.
Go to a drag strip and tell any racer you have something that will create more restriction on his exhaust (backpressure for him), in other words something that will make it harder to get the spent gasses out of his motor and see what kind of reaction you get.
On that note this has been one of the warmest summers in North America and yet I haven't heard anything about global warming.... butter with that corn sir ? We are idiots who keep making the mistakes over and over again expecting different results ( definition of insanity in the dictionary )
Go to a drag strip and tell any racer you have something that will create more restriction on his exhaust (backpressure for him), in other words something that will make it harder to get the spent gasses out of his motor and see what kind of reaction you get.
On that note this has been one of the warmest summers in North America and yet I haven't heard anything about global warming.... butter with that corn sir ? We are idiots who keep making the mistakes over and over again expecting different results ( definition of insanity in the dictionary )
Safety Car
Joined: Jun 2005
Posts: 3,775
Likes: 4
for what its worth, i ran open exhausts with downturns that dumped right behind the tranny crossmember. this was on a stock 350/300hp with 10.25:1 compression. for the first week or two it was pretty nice. shortly after that though, it got to be old as hell and i couldnt wait to put mufflers back on it.
i was 22 at the time also and the cops left me alone. all i got from them was a thumbs up or a wave.
one thing i should mention, it was so damn loud when you got on the gas, i hated bringing it up passed 3-3.5k rpms. and forget about sneaking home late at night in it. when i stopped over at a friends house, he said he could hear me coming from about a block away. he was in his basement with all the windows shut.
i was 22 at the time also and the cops left me alone. all i got from them was a thumbs up or a wave.
one thing i should mention, it was so damn loud when you got on the gas, i hated bringing it up passed 3-3.5k rpms. and forget about sneaking home late at night in it. when i stopped over at a friends house, he said he could hear me coming from about a block away. he was in his basement with all the windows shut.
Last edited by another-user; Aug 13, 2010 at 03:39 AM.
Intermediate
Joined: Jul 2010
Posts: 44
Likes: 0
I ran open headers on my big block for about 4 minutes, it would wake the dead. Get mufflers.
Backpressure is bad, but as long as you have something attached to the exhaust side of the heads, your exhaust valves should be safe.
Backpressure is bad, but as long as you have something attached to the exhaust side of the heads, your exhaust valves should be safe.
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
One of the motorcycle forums I frequent had the same thing questions about backpressure once. Basically, an engine is an air pump. It is all about exhaust sizing. If a pipe is too large the exhaust will cool down before it leaves the pipe and cause the engine to work harder to get the exhaust out. A bend is put in the pipe and that bend causes the exhaust to speed up due to physics and fluid dynamics. This causes the engine to work less to move the same amount of air so it makes more power. The incorrect conclusion is then drawn that the big open pipe didnt cause enough back pressure so it hurt performance. In reality if the pipe were smaller it could be completely straight. At least that is the research that I looked up years ago.
Tech Contributor
Joined: Jun 2004
Posts: 20,834
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Never considered backpressure as being an engine's friend, but that's another topic. In any event, with open headers the pressure you'll receive from your neighbors and the authorities will be your problem. Heck, some tracks and sanctioning bodies even have noise limitations...
Tech Contributor
Joined: Jun 2004
Posts: 20,834
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
One of the motorcycle forums I frequent had the same thing questions about backpressure once. Basically, an engine is an air pump. It is all about exhaust sizing. If a pipe is too large the exhaust will cool down before it leaves the pipe and cause the engine to work harder to get the exhaust out. A bend is put in the pipe and that bend causes the exhaust to speed up due to physics and fluid dynamics. This causes the engine to work less to move the same amount of air so it makes more power. The incorrect conclusion is then drawn that the big open pipe didnt cause enough back pressure so it hurt performance. In reality if the pipe were smaller it could be completely straight. At least that is the research that I looked up years ago.
Intermediate
Joined: Jun 2006
Posts: 47
Likes: 0
One of the motorcycle forums I frequent had the same thing questions about backpressure once. Basically, an engine is an air pump. It is all about exhaust sizing. If a pipe is too large the exhaust will cool down before it leaves the pipe and cause the engine to work harder to get the exhaust out. A bend is put in the pipe and that bend causes the exhaust to speed up due to physics and fluid dynamics. This causes the engine to work less to move the same amount of air so it makes more power. The incorrect conclusion is then drawn that the big open pipe didnt cause enough back pressure so it hurt performance. In reality if the pipe were smaller it could be completely straight. At least that is the research that I looked up years ago.
Scavenging, right?....isn't that why we use header wrap? To keep the hot gases hot and the engine compartment cool?
None the less, Scavenging is different from the back-pressure myth. IMHO nothing about open headers is going to blow up your engine.
I ran open headers for about a week in my corvette...I avoided town driving completely and it took about 5 minutes to get a headache, maybe from the noise, maybe from the carbon monoxide (I don't know, i'm not a doctor)
There is a reason I stopped running open headers, mostly because i like driving my corvette. If all your doing is driving back and forth to car shows then open headers would probably be fine (i doubt the cops would even bother you that much about it).
just my thoughts