1 3/4 vs 1 7/8 headers and ORY what's deciding factor in correct size.
 

I am building a iron LS2 6.0 for my 02 T/A Flat tops, 243 heads and GM ASA cam. Car has a borla adjustable catback on it already. I am really leaning toward going with TSP headers because of how affordable they are. Not looking to drop 1500 on headers and a Y

It will be a daily driver on nice day's and will never go to the track and not real concerned with total HP output. I just want a nice strong running good sounding reliable street DD motor and it does have a stick. With that said

1. What are the tried and proven reasons for going with one size over the other or is there a point at which x amount of mods and cubic inches and cams necessitate the 1 3/4 vs 1 7/8 header choice.

2. How much of a average loss in output if I were to just run OE manifolds and punched out cats on the above.

Keep in mind this combo is for a daily driver w average speed of 0-75 and mostly highway driving and a few WOT back road runs every blue moon or so.

even a stock ls1 will gain with 1-7/8 over 1-3/4. The larger primaries outperform the smaller ones period. They los no torque down low compared to the 1-3/4 and make more power up op so its a no brainer if you're buying new headers.

Also leaving stock manifolds on that car would be a major choking point, I'd estimate on the field of losing 25whp or more by not doing a good set of lt's.

Go 1 7/8"....don't even consider 1 3/4".

As far as fitment, ground clearance and fit and finish what is the consensus on a set of Texas speed 1 7/8 with their ORY for the money they look very well built.

they are a good header and the ory is a nice piece also. I prefer to pay a little extra and get an american made header but you cant really go wrong with any of the 1-7/8 header companies

i love my tsp 1 7/8s, best for price, and they have spikes in the collectors just like kooks....best price i found was 499 shipped from colorado speed....

you could do alot better in cam dept....a 228-232 split duration or some around there would be nicer....i personally would recommend the lunati 227-232 cam, performs very well, its quiet and easy on the valvetrain....

It's a new cam I got stuck with we purchased for a customer. May swap it in the future but just need to get it in and running for now.

I have tsp 1 7/8, one of my first mods. Awesome headers and quality.

Stock sized exhaust valves benefit more from 1 7/8 headers.

Ordered a set of TSP's bout 10 mins ago. Now I'm curious how it will sound with a ORY, borla adjustable catback and a cammed iron LS2 6.0.

Yep.

4 things to consider with headers: primary length, primary diameter, collector length, and exhaust valve/port.

Generally, a 1-3/4" longtube, like LG's Vette headers, make more torque, but they are also quite a bit longer than Kooks/ARH for the Vette. For the F-Body, primary length is sort of what it is due to the frame.

The only tunable variables, then, are the primary diameter, collector length, and optimization for the heads being used. And it turns out the shorter length primaries makes any torque advantage of the 1-3/4" have, moot.

So, that leaves the heads and collector length. Generally the collectors are pretty similar with Kooks, QTP, and ARH having high velocity merge collectors to help pick up midrange torque lost by the shorter primary length.

And as for the heads, 1.55" and 1.575" exhaust valves seem to favor the 1-7/8" at all RPMs. The only exception is AFR with the 1.60" exhaust valve. It's more of a wash on the F-Body, but on the Vette, the longer 1-3/4" primaries made more power (not much, but a little more). Why? Well, the 1.60" valve loses some velocity over the 1.55 or 1.575" valves and the long tube smaller primaries helped reclaim that lost velocity.

To sum it up, primary length is what it is on the F-Body, and most heads favor the larger primaries with no ill effects. The only thing left to decide is which stainless headers you want and if you're willing to pay extra for the HVMC to ratchet up the torque a bit?

Hope everyone brought their umbrella cause it's rainin' cold hard truth in here.

Not that I have heavily reseached the topic but this is the best explanation I have heard on this subject to date. Thanks Jake.

Get the 1 7/8's, just had mine installed couple days ago and love them.

1 7/8's here also. I have the TSP y-pipe with cats welded in. Its alright the clamps they send with it suck so either pony up for some nicer ones or just weld it all together like I did.

Iron LS2 6.0, GM ASA Cam, 243 heads, TSP 1 7/8 LT's ORY and a borla adjustable catback.

Anyone care to venture how loud this thing will be, or if it will sound nice as is.

Sound is subjective -- what sounds great to one might not sound as great to another.

Personally, I like it loud however it MUST have tone (pouring out of a cutout at the headers just sounds loud and louder). I think that setup would sound really good.

I love the deep Borla tone and the LT+ORY will help dial up the volume and you can adjust the plates if you find it's too much. I have a somewhat similar setup and would've gone with the Borla catback over the Magnaflow if I wasn't trying to get under a track's noise restriction.

I hope it sounds nice I want it noticeable but with a good tone. Not a crappy blatty raspy sounding loud.

The rasp will depend a lot on the merge you use for your y pipe. My friend has a borla on his heads/cam LT1 engine and its freakin loud.