beefcake

wow what a difference the 1 7/8 headers made on my car . sounds like a new car. and im not shitting you. its asome can not wait tilli hook up the wires to my qtp cutouts that are at the end of the straight dual pipes!!!

BTL FED

iTrader: (9)

I know what you mean, I had grott 1 3/4 with 3" collectors open header and then switched to Kooks 1 7/8 stepped to 2" with 3.5" collectors and when reved, it sounded like a prostocker

PopaPork

iTrader: (4)

On a stock LS1 would 1 7/8's be to big?

777

iTrader: (21)

yes...you shouldn't need bigger than 1-3/4 unless you go bigger cubes

Neumonic2002

you would basically lose some low end power, probably the only way you would benefit is if you were either FI or stock cubes with stage 3 heads and cam..

Phoenix 5.7

iTrader: (7)

what if you have AFR 205s with a good cam, would 1 7/8 still be too much

777

iTrader: (21)

i would still say that would still be too big of a primary...i'd stay 1-3/4 unless you are running FI and quite a bit of it at that

J-Rod

Correct. You don't need more then 1 3/4 till you get big.

Header pipe length (in inches) = ((850*(360-EVO))/RPM – 3
Header diameter (in inches) = ((cylinder. disp. * 16.38 / ((hdr len + 3) * 25))) * 2.1

EVO is exhaust valve opening @ .006
RPM is peak HP rpm.

TEA Brent

I personally dynotested 1 7/8 to make more power than 1 3/4 on every car i tested. Even at 1200 rpm it makes more trq and power. I tested 1 7/8 kooks everytime over their own 1 3/4 and others 1 3/4. Don't make a mistake, get 7/8 that way your covered until the big motor comes.

matts22

iTrader: (2)

I would be interested in seeing a dyno graph of this. Not because I don't believe you, but because I want to know whether it gained all over the powerband or just peak power. Did it lose power anywhere? I'm specifically talking about a heads/cam car N/A stock bore and stroke.

beefcake

1 7/8 is good for any size ls1. u will loose some low end but will pickup on the top end

Slowhawk

iTrader: (12)

I got the same results.

matts22

iTrader: (2)

Someone post a graph, please!

I really want to see how the curve is affected going from 1 3/4 to 1 7/8.

Sanders

Hmm, thats very interesting. Funny how everyone has always said that 1 7/8 is too big for stock cubes but that isn't the case at all.

Thanks for doing the testing!

JNorris

iTrader: (4)

FWIW in a recent Car Craft, Hotrod, or GM High Tech Performance (I can not remember which) they tested stock manifolds, 1-5/8, 1-3/4, and 1-7/8 headers on a LS1 and the 1-7/8 headers made the most HP and torque.

I know if I ever get rid of my MAC headers I will be going with 1-7/8 headers.

John

LS1LT1

iTrader: (16)

1 7/8" even on a bone stock internal LS1? No losses anywhere?
I wonder now if the same would apply to using a FAST 90mm intake manifold with a 90mm TB, also historically thought to be too much for a stock internal 346. Hmm.

LS1LT1

iTrader: (16)

That article comes up a lot lately. It was Car Craft and they are normally quite a reputable publication but unfortunately those results COMPLETELY negate nearly every single dyno and track test EVER performed on a late model C5 Corvette (LS1 and LS6)...so I must ask, who's lying?

ynkssws6

iTrader: (1)

Is there such a thing as a 1 7/8 with emissions?

01TAFlyer

iTrader: (4)

I think a lot of it has to do is that doing 1 7/8 to 2 or a FAST 90/90 are not going to yield big enough gains (assuming there were gains) to make these cost effective options. A 90mm intake and bigger ports on the headers are usually things done with h/c or afterthoughts of h/c. Just the way I see it, although dyno graphs of this would be interesting.

VaNDaL*SS*

iTrader: (1)

Ive heard that the 1 7/8th headers work very well if ur spraying is this true? and is it worth getting the 1 7/8ths just for that reason, becuase as everyone knows ur not spraying when ur driving normally. I am trying to decide what i am going to get and if i want to get the HVMC's ( high velocity merge collectors)