Just a couple of header questions
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From: Gig Harbor, Wa
Just a couple of header questions What is a good size for primary tubes for a mildly modded LS1? (ie. stock heads, dual exhaust, small cam)
What do stepped primaries do and why would they be desireable?
What is a good primary tube length?
thanks
What do stepped primaries do and why would they be desireable?
What is a good primary tube length?
thanks
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From: Nawf Carolina
Re: Just a couple of header questions 1.75" is the primary tube diameter most use.
Stepped headers increase flow by using a larger primary downstream, but keep the velocity up by using a smaller tube right at the port, this also helps reduce reversion. Not needed if you're doing a mild buildup, unported heads, etc. This is helpful in giving more flow, but keeping ok torque in the mid-range (more velocity generally equals more torque).
Most of the popular long tubes have the longest primaries at 30-32" lengths. Some of the header length calculators will give you numbers like 36 should be the best. I dont know what kind of room you are going to have under that Vette, probably a lot though since it would accept a factory big block.
J.
Stepped headers increase flow by using a larger primary downstream, but keep the velocity up by using a smaller tube right at the port, this also helps reduce reversion. Not needed if you're doing a mild buildup, unported heads, etc. This is helpful in giving more flow, but keeping ok torque in the mid-range (more velocity generally equals more torque).
Most of the popular long tubes have the longest primaries at 30-32" lengths. Some of the header length calculators will give you numbers like 36 should be the best. I dont know what kind of room you are going to have under that Vette, probably a lot though since it would accept a factory big block.
J.
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Re: Just a couple of header questions I am going to have some hooker sidemount headers modified to fit the LS1. They come in either 2 1/8" or 1 7/8". Since the pipes need to be modified, I could easily make them stepped. What diameter should I use and should I step them?
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From: Nawf Carolina
Re: Just a couple of header questions I would definently go with the 1 7/8s. We have a few members here using 1 7/8s, one of them on a bolt on car, so your cammed car shouldn't have a problem <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> The 2 1/8s sound like they are probably for the 454/390 equipped cars?
edit - here is a pic of a stepped header.
<img src="http://www.hedman.com/images/torkhdr-closeup.jpg" alt=" - " />
I guess since you are going to have to cut the primaries at the flange it wouldn't be much more trouble to step it down to 1.75 right there are the port, but I'd try to keep the stock bend, as a crimp/crush bend at that part of a header might really hinder performance.
J.
<small>[ May 27, 2002, 08:48 AM: Message edited by: Crazyquik ]</small>
edit - here is a pic of a stepped header.
<img src="http://www.hedman.com/images/torkhdr-closeup.jpg" alt=" - " />
I guess since you are going to have to cut the primaries at the flange it wouldn't be much more trouble to step it down to 1.75 right there are the port, but I'd try to keep the stock bend, as a crimp/crush bend at that part of a header might really hinder performance.
J.
<small>[ May 27, 2002, 08:48 AM: Message edited by: Crazyquik ]</small>
