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HEADERS : 1 3/4 vs. 1 7/8

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Old 05-14-2013, 11:42 AM   #1
mabryusmc
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Default HEADERS : 1 3/4 vs. 1 7/8

Ok gents, first, I apologize if this has been beaten to death. I have searched and cant really seem to find exactly what Im looking for so I figured I would post up a new thread.

My question.... what would be the difference between these to sizes of headers?

I found a set of 1 7/8 for a good deal... about half as much as I could pick up 1 3/4... and was thinking about snatching them up. I have read that I wont see any additional gain from the 1 7/8, which Im ok with. I have also read that 1 7/8 would be preferred in the future if I plan on FI. With that being said.... will 1 7/8 have any ill effects on a stock LS2 with SLP LMii's?

The wanted end result is to add a little more sound through the exhaust and a little more HP. I just want something a little more subtle until my warranty runs out and I can fork over the $$$$ for FI.

Thanks in advance for any help!
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Old 05-14-2013, 03:01 PM   #2
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no ill effects, it'll just give you some more power and give it a louder roar

and you'd probably need a tune

it would be worth getting some HFCs if you don't already. you're right that if you're going to be going S/C you'll want the 7/8
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Old 05-14-2013, 03:08 PM   #3
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You'll probably make a little less torque compared to 1 3/4

You'll also need a tune to turn off the check engine light after the install, which will void the warranty anyway.
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Old 05-14-2013, 03:35 PM   #4
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Default Rule of Thumb

If your content with second, than go with the larger diameter headers.

If you like first, than go with the smaller diameter headers.

From reading some posts on here from those who build HP 1 3/4" will make more torque which gets you to the finish line first and it's not until 700/800 hp that the larger headers finally inch ahead. Also remember power over the curve.

How much HP is your final setup going to make???

PS: Maybe that's the difference why the guy in second place in the GS bolt-ons with all the same equipment runs 1 7/8" to my 1 3/4" first place.

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Old 05-14-2013, 04:40 PM   #5
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Depends on your future...

I went with the 7/8 and lost tq....I had bolt ons and made good top end power but lost tq in the mid...Now I have a big CAM and again dont have alot of mid tq ....people w/3/4 are making approx 25lb more tq then me but 20-25 less hp...its kind of a trade off...

If I had to do it again I'd prolly stay the same...but...

When I went w/my cam I picked up 60hp and 5lb of tq lol...
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Old 05-14-2013, 04:51 PM   #6
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Either one is fine, but you don't really "need" 1-7/8 headers unless you're doing serious engine work with forced induction. As others have already said, you make slightly more power with the smaller sized primaries in the bolt on cars because they have more back pressure.
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Old 05-14-2013, 05:17 PM   #7
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I would probably buy the cheaper of the two, but as someone already posted, you will lose torque with the bigger headers. I'm not smart enough to know that on my own, so I searched the forums and it seemed a consensus that the 1 3/4 are the better choice and that's why I bought them.
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Old 05-14-2013, 05:21 PM   #8
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Quote:
Originally Posted by mowe View Post
Depends on your future...

I went with the 7/8 and lost tq....I had bolt ons and made good top end power but lost tq in the mid...Now I have a big CAM and again dont have alot of mid tq ....people w/3/4 are making approx 25lb more tq then me but 20-25 less hp...its kind of a trade off...

If I had to do it again I'd prolly stay the same...but...

When I went w/my cam I picked up 60hp and 5lb of tq lol...
I have to call bullcrap on that. 1 7/8 headers will not make 20-25 more horsepower than 1 3/4 headers on a cammed car.
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Old 05-14-2013, 05:46 PM   #9
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Quote:
Originally Posted by FloydSummerOf68 View Post
I have to call bullcrap on that. 1 7/8 headers will not make 20-25 more horsepower than 1 3/4 headers on a cammed car.
I am just going off of what similar cars (ls3's) w/smaller headers and a similar cam... The tq is a trade off for the HP is my pt....they almost wash
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Old 05-14-2013, 06:02 PM   #10
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Quote:
Originally Posted by mowe View Post
I am just going off of what similar cars (ls3's) w/smaller headers and a similar cam... The tq is a trade off for the HP is my pt....they almost wash
this is a before and after dyno with the maff doing the tuning 1 3/4 cattless vs 1 7/8 only a 4 hp gain at 7000 rpm no gain across the band and a 20 rwtq loss and a loss across the whole band. i would think the numbers are pretty high for an LS2 A4 AUTOMATIC big converter and 373 gears. if it gained 4 hp and loss no tq then it would be worth it to me, im not willing to trade off tq
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Old 05-14-2013, 06:13 PM   #11
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I just recently installed 1 3/4 on my ls3. Clearly is not the same as an ls2 but even with the slightly bigger engine I wanted to stick to the smaller header. You don't want to lose mid-range torque on a daily or even a street car. IMO torque is the fun of it!
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Old 05-14-2013, 08:02 PM   #12
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Interesting thread since I going to have a 550 RWH Z06 later this year. It would seem that the 1 3/4 would be the way to go. I always considered the 1 7/8's were automatic, but this thread is making me reconsider.
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Old 05-14-2013, 09:03 PM   #13
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get the 1 7/8 if they are a good deal.
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Old 05-14-2013, 09:46 PM   #14
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I haven't seen enough hard evidence for one over the other.
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Old 05-14-2013, 09:47 PM   #15
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1 3/4 here also because of the torque. I think if you were running at the high end of the RPM range, maybe 1 7/8 would be better, but I like the torque of the smaller pipe. Bigger isn't always better.
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Old 05-14-2013, 09:51 PM   #16
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if they are 1/2 price and you are going fi sounds like you got to get them, but you will feel the tq loss NA, also removing the catts will make it sound great
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Old 05-14-2013, 09:58 PM   #17
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Quote:
Originally Posted by dennis50nj View Post
if they are 1/2 price and you are going fi sounds like you got to get them, but you will feel the tq loss NA, also removing the catts will make it sound great
I ran the offroad for 4 years and the sound was off the hook but I tired of the stench and went back to hi-flows.
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Old 05-14-2013, 10:22 PM   #18
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Quote:
Originally Posted by saplumr View Post
I haven't seen enough hard evidence for one over the other.
I only tried one set, but would love to try other brands to dyno and track test

Quote:
Originally Posted by saplumr View Post
I ran the offroad for 4 years and the sound was off the hook but I tired of the stench and went back to hi-flows.
i remember you saying that, i am cattless and can smell the fuel strong burning the eyes yet the set of 1 7/8 i tried had highflow catts that i could shin a 9 bulb led light threw and see all 9 bulbs clearly and they made more hp and no fumes no burning eyes, and also quieter
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Old 05-15-2013, 12:14 AM   #19
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Quote:
Originally Posted by dennis50nj View Post
this is a before and after dyno with the maff doing the tuning 1 3/4 cattless vs 1 7/8 only a 4 hp gain at 7000 rpm no gain across the band and a 20 rwtq loss and a loss across the whole band. i would think the numbers are pretty high for an LS2 A4 AUTOMATIC big converter and 373 gears. if it gained 4 hp and loss no tq then it would be worth it to me, im not willing to trade off tq
If this is an LS2, making that much power, he had a whole lot more than gears, stall and headers. That's a bunch of HP for an LS2 with bolt ons.

For what it's worth, with my bolt ons, my dynojet torque numbers were 3/10s foot pounds short of 400. That's a lot of torque for the size of that motor. HP was 389. I run 1 3/4 headers too.

Last edited by ParisTNDude; 05-15-2013 at 12:17 AM.
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Old 05-15-2013, 02:22 AM   #20
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Torque is what moves a car from point A to B, by the time the larger headers make those few extra hp at the very top than lose it with each gear change the smaller header car is at the finish line lighting up his victory cigar!

REMEMBER, OVER THE CURVE, THAT'S WHERE YOUR ENGINE SPENDS MOST OF IT'S TIME.

Last edited by C7/Z06 Man; 05-15-2013 at 02:50 AM.
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