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!

no ill effects, it'll just give you some more power and give it a louder roar :thumbs:

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

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.

Rule of Thumb
 

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

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

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.

:cool: How much HP is your final setup going to make??? :cheers:

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.

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...

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.

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.

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

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.:thumbs: if it gained 4 hp and loss no tq then it would be worth it to me, im not willing to trade off tq
http://i49.photobucket.com/albums/f2...headers001.jpg

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!

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.

get the 1 7/8 if they are a good deal.

I haven't seen enough hard evidence for one over the other.

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.

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:yesnod:

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.

:iagree:I only tried one set, but would love to try other brands to dyno and track test

:iagree: 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 :yesnod:

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.

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! :D :yesnod::lol: :cheers:

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

If you have a stock engine and all you are doing is adding1 7/8 headers, you may not be happy with the results. You may actually have less power.

http://i254.photobucket.com/albums/h...ps5532d0ed.jpg

:lol::lol:yes he did have more then that, its my car LS2 with bolt/ons cartek H&C, i was just stating that usually you lose hp with gears and big stall converters, how much i don't know, most sticks go from 342- 410s and lose 7-10 hp i have read, so how much does the automatic lose, 315 to 373=58 same as 342-410=58 273 to 373=98 :eek:so does the optional 315 gear dyno less off the assembly line? over the standard 4l65 273 and the standard 342 m6 also the standard 256 a6

I think you're thinking of area under the curve. Assuming correct gearing/similar weight the biggest area under the hp/tq curve will win the race.

If you are serious about FI and big power I wouldnt be afraid of the 1 7/8. Even if its a little down on tq just pulley up and boom its back. When you make bigger power(I dont know how much) the bigger primaries will be your friend.

My experience with 1 3/4 and 1 7/8 on my deceased blower car. I made 7 more hp and 9 tq with the larger headers, lost a tad in the lower range but did not notice with the boost either a gain or loss, but I liked the sound better with AR headers.

N/A 1 3/4 are best for hp and tq where you use it mostly.

:cool: I like curves, whether I'm over or under them. :lol:

You are right, it's referred to as under the curve and the only way that makes sense to me is that there is "nothing" above the curve. :D

AWESOME GENTS! this is exactly what I was looking for. While the price tag did look pretty good at first.... after reading everything I think I might just pony up the $$$$ and get the 1 3/4. Its a weekend warrior car and I dont push her hard enough to really use the TOP end and even if I did FI id would be a ways down the road.

Thanks again gents!

Smart move....

I'd save the money and get the cheaper headers.

For a cammed/heads/intake Ls motor...the 1 3/4 is ideal. There are two things making power and torque, one is flow and the other is the scavenging. So there is an optimal size, not just bigger is better. We could have offered the 1 7/8 first if the engineers found it produced more power. For big blower setups, I understand the need of 1 7/8, 2", ect. But we are talking 900+HP. We are about to offer the 1 7/8 in our Tri-Y design....I pretty much see my days convincing my customers to get the 1 3/4:salute:


http://www.pfadtracing.com/photos/da...rvette_Sig.jpg

Interesting thread. I just had my shoppe install the Kooks catted 1 7/8 long pipe with x pipe, Callaway CAI on my 2008 C6 A6 at 35k miles with a new tune since we had been discussing a blower in the future. I got the dyno to 411rwhp with a 408 torque reading. From other posts these numbers seem decent. I love the way the car sounds and runs with much better accelaration and torque compared to pre mods for sure.

It seems you can't go wrong with either set up compared to staying stock. Good Luck with your choice.

There are a lot of good headers out there. As important is the shoppe you work with if your having the install work done. Just my .02

Not true with the LS3 :yesnod:

1-7/8" make more power everywhere with a 4 into 1 header :thumbs:

I said torque and you said power.

A 1 7/8 is not a good idea for a max-effort setup unless you're making crazy power. Like PFADT said, 900+

On my virtually stock ls2 (CAI, tune, DR) I went 12.2 at 115mph. With just the addition of 1 7/8 LG Longtubes and a retune the car went 11.6 at 118mph in worse air. Yes the 1 3/4 may make a little more torque under the curve, but you wont lose power or torque anywhere compared to stock manifolds. The car was still very snappy and fun to drive around with more power everywhere in the powerband. If I were to do it again I would still go with the 1 7/8.

1-7/8" make more torque and hp all the way from idle to redline on the LS3 with a 4 into 1 header setup. I have tuned about 30 cars that made the swap and none of them lost anything to the 1-3/4" headers anywhere.

True with a tri-y design the 1-3/4" diameter header is sufficient for the LS3. I ran a set of 1-3/4" tri-y's on my LS3 powered GXP and they made comprable (but not more) power as 1-7/8" headers that I replaced them with.

By purchasing 1-3/4" headers in a 4 into 1 design you gain nothing and lose room to upgrade down the road. IMO not a smart decision :thumbs:

Usually when your making more torque "under the curve" you are usually making more hp too.

CHECK THE DYNO SHEET GRAPH. PAGE 1

The graph is of an LS2 C6 I am not disputing 1-3/4 is better for that application. LS1 and LS2 cars should use 1-3/4" headers unless going heads/cam or FI.

The LS3 is different than the LS1/2 in that it does not lose bottom end power for an extra punch up top. It simply makes more power everywhere (hp and tq).

LS1/2 = 1-3/4"
LS3/7 = 1-7/8"

Hope this clears things up :cheers:

Just a general statement.

I'm going to do with Pfadt's actual research over 30 cars tuned. Thanks though.

Tri-y design doesn't require the same size primary as a 4-1 design to make good power - you're missing the point :yesnod:

LS2 = 1-3/4"
LS3 = 1-7/8"

** with a 4-1 header which is what most manufacturers make

I don't care if you believe me or not get the smaller headers if you have an LS3 and go slower :thumbs:

Great read. I went with 1-7/8" due to me being Heads/Cam/FI (750rwhp). It seems like the general consensus is 1-3/4" for N/A bolt-on cars, and 1-7/8" for high power builds (700+). Bigger is not always better, just depends on your end goals.

I wish we had actual dynos of the same LS3 car with each size! I can't seem to find anything.

I posted a similar thread (regarding LG streets 1 3/4 vs. Texas Speed 1 7/8) for my bolt on 05. I am adding a FAST 102 at the same time and probably a cam later on. The Texas Speed headers/x are a great deal, saving around $500 to go that route instead of the LG's. This thread as well as info posted in my thread have led me to lean towards the 1 3/4.

05Z51C6: The FAST 102 is a nice mod - http://forums.corvetteforum.com/c6-t...st-intake.html

Its very simple in my eyes..


NA LS3

FORCED INDUCTION /NITROUS = 1 7/8

NA: 1 3/4

Will you make max HP in an NA application w/ 1 3/4 ? NO but you will make more TQ and HP under the curve...MORE TQ then HP ...that will be the biggest notice

:cool: From what I have read here posted by Pfadt (for one example) is that it's the amount of HP that the car will make i.e. 900+ that will decide what size primary header tubes to use, PERIOD... :flag:

Intake swap also maybe? Stock intakes don't typically peak that high.

Looks like it lost HP & Torque across the whole band! and only gained that 4 hp at the very end on just the one pull of the two; also looks like a 25/30 HP loss @4500 RPM'S to me with the 1 7/8" headers & about a 50 HP loss if you use the lower 1 7/8" header pull. WOW!!

ported fast 90:thumbs:

:iagree:
:yesnod:that was with no tuning changes, we let the cars computer adjust and those were after it adjusted, i would love to try some other brands if some companies would like to step up!!! i would hate to do this test and only the kooks prove to show tq and hp gains with no loss. I know it would be great for business if the 1 7/8 header could put a H&C C6 automatic into the 500rwhp range:thumbs:

:rofl: More important is that they are 3 inch (x-pipe) catback over 2 1/2 catback. Oh by the way it's power UNDER the curve.
Whats the FIRST PLACE STUFF!

Don't believe everything you read! Plus PFADT is new to the header game. Here is 1 3/4 with 2 1/2 x-pipe vs 1 7/8 with 3inch x-pipe.
A&A kit and the SAME tune!
http://i251.photobucket.com/albums/g...e/scan0007.jpg

I run 1 3/4" SS headers with a 3" X-pipe & no cats back to 2 1/2" stock (430 hp) LS3 mufflers.

This thread I believe is about "header size" with the rest of the system the same and not apples and coconuts. :D

always love this debate btw..haha

No right or wrong answer, the decision to choose 1-3/4" or 1-7/8" should be decided on a few factors such as how you actually use the car, what current modifications the car has and where you want to be in the future. Seems like these questions/answers aren't commented enough. Next set of questions are based around how long do you plan on keeping the car, how many miles do you drive per year and what your budget is. If you put a lot of miles on the car you should be choosing a stainless steel header with lifetime warranty, otherwise save the money. Obviously we could go on and on, like who will do the install and what about the tune??

Sorry just our 2 cents as there are many important components to look at besides basic primary size. Thanks for listening.

Paul G.
Stainless Works

I was told by my tuner to get 1 3/4 headers, then I decided to go with a mild cam. Tuner said better get a 1 7/8 header and a 160 thermostat at this point, sound about right? Cam must have made a difference.

Does the cam have an aggressive profile? A cam will change the volumetric efficiency of the engine, slightly but all depends on cam specs. Again, all depends on how you use the car. If its just a cam, use 1-3/4". Seems like the cam is probably mild since you didn't mention upgrades heads and intake.

vararam Intake, cam is 232/234 .595/.598 comp cam grind

Lol, you took the words right out of my mouth in regards to that graph.

There is/was something horribly wrong with that car in the first pull if the only change was headers.

my guess is that for 98% of the people the decision between 3/4" and 7/8" won't make a difference nor will it be noticed in daily driving. if you are going to go cam or supercharger in the future or if you are not sure then go 7/8's.

I installed my own parts this dyno is
Kook's 1 3/4 with 2 1/2 inch x-pipe.
Switched to ARH 1 7/8's with 3 inch x-pipe.
Then redyno'd on the same tune. No one pulling ANY LEGS HERE!
The obvious here is the 2 and 1/2 xpipe sucks on a blower car.

Everyone says Phaft says this! Nick at ARH which has sold 10,000
to one of Phaht's. Tells you the 1 7/8 beats the 1 3/4. Plus PHA
FT's Tri-y opens up quickly from 1 3/4.

:rofl: :lol: So wrong! :rofl:

Yeah, but I isn't always about the power is it! To me the sound is the main selling point.

The true answer is...what is best for one person, is not always best for another. For anyone who is considering doing a build and trying to decide what size headers to use, I feel the best thing to do is contact the companies you are considering working with and outlining your build to them. This way, we can determine what is best for you and your application.
http://www.pfadtracing.com/photos/da...rvette_Sig.jpg

After reading through all of the posts...I feel compelled to post this dyno. This was performed by one of the forum vendors.....not by us...and this is a vendor I know you guys all respect when it comes to making power:

http://www.pfadtracing.com/photos/da..._vs_4into1.jpg


This is for a stock application, and take it for what its worth

End of the day the dyno has nothing wrong.
Bunch of different sizes??? What sizes are there except for 1 7/8 and 1 3/4. Plus if you think about it 2 1/2 is too small for the x-pipe
:willy: Headers is a nice addition to FI cars! Must be because no one adds FI without headers. :thumbs: