RowboatLS3

Which size headers would be the ones to go with? Plans with the car is intake, header, exhaust, cam, maybe heads, nitrous and tune. Which would be the better of the two to go with? Thanks

robertf97

I would use 1 7/8" and wouldn't buy them until I had the cam and heads.

From the fast list a C7 can go 10.39@131.48 mph with stock exhaust. I don't think it makes any practical performance difference between 1 7/8 and 2 inch headers until you are in the 9's.

I chose 1 7/8" for street use because I didn't want to risk any low end loss and have more clearance.

WKMCD

FWIW: I went to Carlisle to have a set of ARH 1 7/8 LT's installed on my car. After talking with Nick, he convinced me to go with the 1 3/4 on the LT1. I told him it would end up with 7-8lbs of boost and he quoted one of his larger vendors and forum sponsor here who said they lost HP and it moved the power band up when they changed to 1 7/8 from 1 3/4. Unless you're running 14-15lbs of boost according to Nick, run the 1 3/4.

I'm very happy with the 1 3/4.

Just my $.02

Higgs Boson

It's funny because you will also find dynos of cars making power with 2". It wasn't long ago that 7/8 was the big size and 3/4 was normal.

On a bone stock car 3/4 makes good sense.
On a modded NA engine one could make a case for 3/4 or 7/8.
On a boosted car one could make a case for 7/8 or 2.

It seems we are talking about the difference of 5-10 HP at any given area of the RPM range, one being higher in one place but lower in another.....I am not sure it really matters which one you choose as long as you don't err in the extreme wrong direction (2" on a stock motor).

It's like buying a ZX6R or a GSXR600 or CBR600. Which one looks better to you? You won't outrun yourself on one vs the other.

RowboatLS3

Ill end up going with the 1 7/8 headers then. I know the car wont see that much boost but it will see some nitrous, heads, and cam so might as well go one step up from the "normal". thanks for the input everyone.

Cordes Performance Racing

Our 2'' headers picked up hp and tq everywhere, Lashway did a completely independent test of them and we posted up the results.

0ChucksTuning

2" on everything we do. Same as above, pick up everywhere over stock. Never heard of a 1 3/4 for a C7.

runutzzzzz

I don't know first hand nor do I have any knowledge on the subject but I've been told by two different tuners that larger is better on a modded car.

Higgs Boson

picked up everywhere over stock manifolds, but how did they compare with 7/8?

at full throttle from 2000 and up?

and most importantly but often overlooked, what the dyno doesn't measure.....

part throttle transitions, throttle response, and basically everything that isn't wot.

I'm not posting to argue, but because no one measures the 2500 30% throttle to 80% throttle transition or anything like that.

Ben@WeaponX

I usually do 2" on my client's cars too for boosted. Most of those are 12psi+ though.

I went with 2" on my LT1 427 with plans for a lot of nitrous on top.

Cordes Performance Racing

Haven't done a back to back with 1 7/8 so don't know. I also will put money on the table you couldn't tell a mid throttle transition difference between a 1 7/8 vs 2'' even if one made a slight difference in tq compared to the other, that is one of the strangest things I have ever seen posted.

Higgs Boson

many things we have never considered seem strange at first.

and I would be willing to take that bet. I am talking about a normal street driving scenario, or a hill country/canyon road situation where you aren't in 3rd gear at 75, but fifth or sixth.

on a racetrack where you keep rpms up high and push at 9 or 10/10th, yes I can see not telling a difference as throttle transitions are faster the higher the rpms are.

I would just hate for someone to play the wrong hand when they mostly cruise around and occasionally punch it rather than be a drag race every weekend kind of person.

with that said, my 9 second Nhra/IHRA super stock car (naturally aspirated) doesn't run 2" primaries and it doesn't do anything but wide open throttle except when I pull it in the trailer.

I would love to see a back to back with header sizes (all else equal), it's the only way to know for sure, money exposed on the table or not. I need to buy a set of long tubes, but not in a vacuum.

Cordes Performance Racing

Higgs is your 9 second car a big stalled, big gear, light auto car? If so don't be that guy that says I have this one car that does this, therefore I have it all figured out. One of our personal cars is a 580 rwhp stroked ls3 in a light fbody that's na in a stalled auto that runs deep into the 9's, he has arh 2" headers. See that is more relevant to this being that it is probably more related motor wise to the lt, then what you have in your drag car. I'm not saying you don't have the knowledge to have a good discussion here but use relevant things. We proved they don't loose tq or hp anywhere and the quality put into these far surpasses anything else out there.