1 7/8 AR Headers on a lightly modded ls1
03-25-2008, 01:03 AM
#1
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1 7/8 AR Headers on a lightly modded ls1 like the title says, i have a fast 90 90 setup and and exhaust and thats basicaly it, besides the slp lid and kn filter, is this header system over kill, eventualy im gonna go with a 408, but i would like to install some headers now and not have to buy new ones when i get my 408, will 1 7/8 headers benefit my ls1
03-25-2008, 01:16 AM
#2
Nice timing, I am having this exact set of headers put on mine tomorrow. Overkill? Maybe. My theory is this: Bigger primaries can only provide better flow, hard to see a downside, especially since there is no consensus to speak of on "backpressure." (I wish I had a FAST, nice choice) My supporting thoughts and evidence:
-LOTS of GTO and LS2 guys use this size header with NO ill effects, specifically to torque or MPG.
-I am going from MAC mids (less than 1 3/4) and ORY to the ARH and catted Y. I think I should pick up power and torque, lose the rasp, quieten but deepen the note, and have less noise at the engine (thicker tube gauge).
-My SLP dual/dual provides a constantly good flow and "normal" volume levels: best of both worlds without dropping big coin on a 3" dual setup with cats and 4 mufflers.
-Fact is, no cats = bad smell and leaky primary/collector makes it just gawd awful.
-Finally, I do plan to go bigger eventually and want these to be my last set of headers.
Hopefully, I'll be right. We'll see.
If I think about it, I'll grab some video clips before and after.
EDIT:
No video but dynos before and after here:
https://ls1tech.com/forums/showthrea...45#post9136045
-LOTS of GTO and LS2 guys use this size header with NO ill effects, specifically to torque or MPG.
-I am going from MAC mids (less than 1 3/4) and ORY to the ARH and catted Y. I think I should pick up power and torque, lose the rasp, quieten but deepen the note, and have less noise at the engine (thicker tube gauge).
-My SLP dual/dual provides a constantly good flow and "normal" volume levels: best of both worlds without dropping big coin on a 3" dual setup with cats and 4 mufflers.
-Fact is, no cats = bad smell and leaky primary/collector makes it just gawd awful.
-Finally, I do plan to go bigger eventually and want these to be my last set of headers.
Hopefully, I'll be right. We'll see.
If I think about it, I'll grab some video clips before and after.
EDIT:
No video but dynos before and after here:
https://ls1tech.com/forums/showthrea...45#post9136045
Last edited by jmilz28; 04-11-2008 at 10:59 PM. Reason: NEW RELEVANT INFO
03-25-2008, 06:24 PM
#10
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In short, you should see better gains out of a 1 3/4 header than a 1 7/8 header with a stock to lightly modded F-body. "More flow" is only good up to a point. After awhile, it'll start to hurt you. That's why 1 7/8 headers tend to kill your low end. The flow is too great and exhaust velocity suffers.
Even too much water will kill you. Nothing is good in excess.
Of course, this is all dependent on your future goals for the car. If you intend to add a D1SC or something, well then 1 7/8 headers are a great idea. If you don't plan on doing anything more than intake, exhaust and a small cam, well, it may be a bad idea.
03-25-2008, 08:40 PM
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id say go with the 1 3/4 for now and buy a decent set that will sell well later (kooks, ARH, dynatech). im with ya on the whole thinking ahead thing. but i think in this case it maybe an over kill.
03-25-2008, 09:22 PM
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Is getting a 408 eventually mean............2months....6months......12monts... .....2years......3years you get the point. I mean I eventually want a 408 too, but I know its going to be a while. If it is get the 1 3/4.
03-25-2008, 10:40 PM
#15
Ok, I've driven about 50 miles and here's my SOTP impression:
1. No smell
2. Quieter, slightly
3. Feels the same overall, powerwise.
I had LCA relo brackets done so how easy it "breaks loose" is not an accurate gauge.
I feel like I lost no torque and gained MAYBE a tiny bit of HP. Overall, I think adding the diameter but adding cats made it a wash. Fact is, it will get retuned and re-dynoed later this week. Only changes from last dyno are the ARH 1 7/8 long tubes and catted Y. Once it's tuned, we'll have the graph, apples to apples, to compare. I feel that not being retuned is costing me a bit of potential. Really and truly, the car drives the same from an acceleration standpoint - without a retune.
I'll post the graphs before and after once retuned for you guys to see. On LS2s, with a tune, Speed Inc seems to think you gain all over - even with headers that are considered "too big" by many. My bet is that will hold for LS1s too, but the graphs will tell us.
Stay tuned...
Smokin, I'm not trying to hijack but only want to offer my specific experience as it develops since you are looking at the exact same setup. If you want me to start a new thread, let me know.
1. No smell
2. Quieter, slightly
3. Feels the same overall, powerwise.
I had LCA relo brackets done so how easy it "breaks loose" is not an accurate gauge.
I feel like I lost no torque and gained MAYBE a tiny bit of HP. Overall, I think adding the diameter but adding cats made it a wash. Fact is, it will get retuned and re-dynoed later this week. Only changes from last dyno are the ARH 1 7/8 long tubes and catted Y. Once it's tuned, we'll have the graph, apples to apples, to compare. I feel that not being retuned is costing me a bit of potential. Really and truly, the car drives the same from an acceleration standpoint - without a retune.
I'll post the graphs before and after once retuned for you guys to see. On LS2s, with a tune, Speed Inc seems to think you gain all over - even with headers that are considered "too big" by many. My bet is that will hold for LS1s too, but the graphs will tell us.
Stay tuned...
Smokin, I'm not trying to hijack but only want to offer my specific experience as it develops since you are looking at the exact same setup. If you want me to start a new thread, let me know.
03-26-2008, 10:55 AM
#18
I ran 1 3/4-1 7/8" with 3 1/2 HVMC on my bolt on car, and now currently cam only and I can't say there is any adverse side effects, not to mention my bolt on only car(NO fast 90/or E water pump) through 9" rear still made 353rwhp/357rwtq. IMO much of the advice given in this thread is worth exactly what you paid for it, and thats nothing.
I love how people are making a big deal about 1 7/8" primaries being too large like its really gonna have a huge effect on performance and torque output. Even if there is a minor loss compared to a 1 3/4-3" collector header it will be insignificant on a bolt on car, its not like it will negate the whole gain of the header swap anyways. Planning ahead to meet current and future goals is smart. When your shelling out that much money for headers, why would u want to do it more then once.
I love how people are making a big deal about 1 7/8" primaries being too large like its really gonna have a huge effect on performance and torque output. Even if there is a minor loss compared to a 1 3/4-3" collector header it will be insignificant on a bolt on car, its not like it will negate the whole gain of the header swap anyways. Planning ahead to meet current and future goals is smart. When your shelling out that much money for headers, why would u want to do it more then once.
03-26-2008, 11:04 AM
#19
A 1.75 AR header would make the same peak power and a bunch more under the curve.....alot better throttle response as well.
Would a 1.875 header make more power than stock manifolds....of course....its just the wrong choice for most 346 combo's, even reasonably aggressive ones with good heads/cam packages.
IMO the smarter move is to do what a few others have mentioned....get the right header now (the 1.75) and get the right header later (the 1.875).....most big inch "dream projects" take twice as long as you think (ask me how I know...LOL).
Down the road you can sell your 1.75 headers and probably recoupe a fair amount of your purchase price so the cost of ownership in the right header isnt as bad as you think and you reap the returns of having the right header every day....which will likely be alot more days than you think.
Tony
Would a 1.875 header make more power than stock manifolds....of course....its just the wrong choice for most 346 combo's, even reasonably aggressive ones with good heads/cam packages.
IMO the smarter move is to do what a few others have mentioned....get the right header now (the 1.75) and get the right header later (the 1.875).....most big inch "dream projects" take twice as long as you think (ask me how I know...LOL).
Down the road you can sell your 1.75 headers and probably recoupe a fair amount of your purchase price so the cost of ownership in the right header isnt as bad as you think and you reap the returns of having the right header every day....which will likely be alot more days than you think.
Tony
03-26-2008, 11:06 AM
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I got them on a very lightly modded Ls1 and running 12's at 113mph on stock suspension and tires. I would say they work well on a near stock ls1. My car got a nice gain. I ran 13.20 at 110. before the headers and just the headers and catted Y on a stock tune I went to a 12.85 @ 113. with a 2.19 60'. spinning bad I say go for them. Just talk to Nick at ARH he will steer you in the right direction.
Last edited by 2002_z28_m6; 03-27-2008 at 07:10 AM.