LS1Sacrelig

iTrader: (5)

Im almost finished assembling all of my parts to put my ls1 in my s13 240sx, and im curious as to pros and cons of these header options...My enigine set up is a 99 LS1 bored 10 over, ARP everything, 853 heads that have been worked, TSP MS3 112 cam, LS6 intake, 42# injectors, and BBK 80mm TB. I am shooting for mid 400whp and I have the two header options from Sikky, just wondering if you guys think the increased primary size would be beneficial or not neccesary.

Thanks,
Phil

dr_whigham

iTrader: (49)

ALWAYS get the bigger primary. You won't lose a thing down low, and you'll gain higher. It's been proven time and again on here.

1 7/8" all the way!

03Sssnake

iTrader: (20)

without a doubt

Sales2@Texas-speed

iTrader: (5)

Agreed, especially with the aggressive heads/cam combo you're running, get the bigger headers!

LS1Sacrelig

iTrader: (5)

Thanks guys, 1 7/8" it is! think mid 400s is realistic with that setup?

yesaCSpencer

iTrader: (3)

I think your power goals are attainable with that setup. That things gonna be a rocket! I have an LS1 S14

LS1Sacrelig

iTrader: (5)

Hell yea! Whats done to yours? I havent seen another one in person besides a drift car at NOPI, love to ride in one, besides mine which ive been waitin over 2 yrs to get done...

mjs1012

iTrader: (36)

get the bigger primaries. let that cam breathe

187fl

Just wanted to jump into the conversation. When I bough my headers a few years ago (arh 1 3/4) I didn't do much research and just went with the smaller ones. I am now looking to do a head and cam package. Would this be a problem or will i have to go with 1 7/8?

dr_whigham

iTrader: (49)

Just a thought, you could always sell your 1 3/4" and only minimally be out of pocket for the bigger primaries....

187fl

You're right. I will still put the heads and cam first and then sell em.

2win_SS

iTrader: (1)

^^^ you will be fine... But BIGGER is BETTER in this case... One of the guys from TSP wrote a thread about the test they had between the two headers and they had a gain goin from 1 3/4 to 1 7/8... I can't find it right now but I'm sure one of the guys from TSP can fill in the rest... You probably squeeze out mid 400hp with that setup... PRC 2.5 LS6 heads would be ideal for that MS3... My opinion.

therabidweasel

iTrader: (5)

That comparison used two different header designs and showed something like +7/+5 at 6500rpm at the crank. At 3000rpm HP was the same and torque was -6. The weird thing was that the -6 was called insignificant while the +5 was significant. Bottom line is it was an apples to different apples comparison that showed moderate if any increase. Not a terribly compelling argument for 1 7/8 imo.

TransAmcoupe98

iTrader: (10)

Thats not true...otherwise everyone would just stop making 1 3/4 primaries. You do in fact lose down low, but you will gain some HP up top depending on your setup. Going with too big of a primary can have adverse effects on a setup. Generally people run the 1 7/8 when they anticipate well over 550 whp. Im sure this will start an argument so here is a thread to go ahead and read for yourself OP and make your decision. Bigger ISNT always better, just like choosing a cam. There is a lot of misinformation on these boards so do your research and don't just go off someone word or opinion. There are numerous cases of people going to big with headers and hindering their setups. Here is one for example, read thread below...
https://ls1tech.com/forums/generatio...xperience.html


Now, if you are going to be using nitrous or forced induction, this is a different case. Those setups feed off free flowing exhaust and there is power to be gained with 1 7/8. HOWEVER, if you already have a set of 1 3/4 primaries on your setup, it isn't worth spending the money and time taking them off and putting on 1 7/8''. Gains would be fairly minimal. Again, this goes for your forced induction setups. Here is a thread to support this claim. Keep in mind when you read this thread, the guy swapped his 1 3/4 for 1 7/8 and made a little gain down low but he has a forced induction setup. Even then, the gains were pretty minimal.http://www.smokinvette.com/corvettef...ad.php?t=27830

Again OP, do your research on this. In my opinion, you should go with a set of 1 3/4'' on your setup. Going with 1 7/8'' will do nothing for you and probably hinder performance to an extent. I do have personal experience in this so feel free to PM with questions...In the end, we are all just holding the tail on this dog...youre the one screwing it.

ss4chad

iTrader: (26)

So for my own peice of mind and to protect the money I have already sunk into my car fund:
My new Darton Sleeved 427 with a:
Comp 256/264 - 625/625 - 113+4
Dart 250-68 2.08/1.60 head
Harland Sharp rockers
ported FAST 90
Holley 90TB
Flow matched 42lb Ford green tops
Dragonslayer 4" stroke crank
Diamond Dome pistons
all being squeezed and forced into my freshly JET HOT coated 1 3/4 Kooks LT's is not going to work well? I should sell them and get 1 7/8 or stepped headers?
Or will the 1 3/4 be sufficient?
I plan on running dual 2 1/2 oval tubing over the axle and into a single muffler and out as 2 1/2 duals with slash cut tips at the rear of the car.
Anyone see a problem with this set up? If so then why? I may need to do some more saving before dropping this set up in the car.

Chad

TransAmcoupe98

iTrader: (10)

PM sent ^

dr_whigham

iTrader: (49)

The posts you put up were of C5's, brother. They have screwy 1 7/8" headers to begin with, and even state so in the "my experience" thread you posted. Primary length has a lot to do with it as well.

Nissan LS240

iTrader: (1)

I don't think it will matter a whole lot but if you haven't gotten them get the 1 7/8, I use the 1 3/4, didn't think I was going to put a whole lot of parts on it, but I still made almost 500rwhp

187fl

Good input, I will definitely wait on getting new headers cause ARH's aren't cheap. I will cross that bridge when I get there.

TransAmcoupe98

iTrader: (10)

Granted, but to go ahead and say get the 1 7/8'' no matter what the setup simply isn't true. Someone with a fairly mild setup such as a cam only would benefit with 1 3/4''. I have heavy experience in the corvette world, but I have been though f-bodies as well. Again, this is just my opinion as everyone has their own. Take it for what its worth.