1 7/8 LT's on a SI LS1?
 

I have been reading up on which LT header 1 3/4 or 1 7/8 makes more power on a stock internal ls1. It seems the most recent posts show that the 1 7/8 still show gains. My concern is I just ordered a set of kooks 1 7/8 LT's w/ the kooks 3" true dual setup. It will take 2-4 weeks to complete, so I can still change if need be. My logic on purchasing the 1 7/8 was to leave room for growth. Right now Im just normal bolt-ons other than 1.85 rockers/918 springs. I will be installing a fti 3800 converter when the exhaust gets installed. Next mod in the future will be a n2o outlet wet plate or the whipple 2.9 f-body kit, when and if it's released...other than that Im pretty much plan on staying stock internal...I might do a small cam but most likely not. So am I on the right track or should I change the order to the 1 3/4 LT's? Thanks

It won't hurt anything going with the 1-7/8" primaries at this point - I've been running them on my bolt-ons only '02 Camaro for the better part of the past two years. Prior to that, I was running Kooks 1-3/4" headers. The 1-7/8" primaries are a bit tighter, but everything still cleared just fine, and the install went smoothly. As an added bonus, the collectors ended in the same spot, so I bolted my existing exhaust right up and was on my way.

Performance-wise, I didn't really notice anything one way or another, but wasn't really expecting to (I didn't do a back-to-back dyno though). It'll definitely leave me room to grow down the road, and that's what I was really after.

I wish I would have went with 1 7/8 when I bought mine years ago. From talking with my tuner the 1 3/4 don't really become a restriction until around 440 rwhp, but i've never heard anything negative about 1 7/8 on a bolt-on car. I just did H/C so I'll be switching soon.

Thanks for the replies! I have hooker 1 3/4 now and they are about rusted out and the car never sees rain or snow lol. I figured might aswell get the stainless 1 7/8 and never buy headers again. My only concern, which is why I post this thread,, because a well repected member(Mr. Tony Mamo) posted in a older thread that they would hurt tq significantly in the lower rpms. But then texas speed did a dyno comparison between thier 1 7/8 vs pacesetter 1 3/4 and they picked up power everywhere. I leaning towards it being a myth, just like the fast 102 hurting power on a 346 myth that was busted.

Maybe that is without a tune?

Part throttle isn't as crisp to me as it was with the 1-3/4" headers, but that isn't something that would show up on a dyno since a dyno only shows WOT. I don't miss it much since my 4.11s out back make traction an issue by itself, and I also have a fairly lightweight clutch assembly that makes things a bit peppier too around town.

I didn't buy them for the engine currently in my car (like I said - bolt-ons only), but for the engine I'm planning to build on down the line. Any gains/losses switching between the two wasn't enough for me to be concerned, and I wouldn't hesitate to do it again.

No im pretty sure it was tuned, but he is the only one that I have seen to post such results.... I would post a link but now I cant find the thread lol. it was back in 2006

na im not to worried about it either... I dont daily drive the car, so a little less throttle response won't bother me. Besides when the stall goes in, any gains/losses under 3k will be pointless.

In testing (DJ), the 1 7/8 consistently showed gains everywhere over the 1 3/4. Anything else is more internet misinformation.

Does anybody have links to the comparisons?

I am also running Pacesetter 1 3/4" headers that were on the car when I bought it. They are rusting away and Id like to swap to a set of stainless steel. I figure I would bump up to 1 7/8" if it would be worth it tho. I'm currently around 410whp on a stock bottom end LS1. I don't want to lose low end just to gain a tad bit of mid and top end, so visual comparisons would help me decide.

https://ls1tech.com/forums/dynamomet...s-1-7-8-a.html

https://ls1tech.com/forums/generatio...o-results.html

Good decision. Hope you got the package for a good deal, that is a TON of money to spend. With any FI or nitrous, the 1 7/8" will certainly be worth it.

I love the 1 7/8 on mine. It defintely does NOT lack for tq down low... It snaps your neck when you nail the throttle. Of course the stall helps that, but the engine is making mad tq.

^good to know! Thanks

Thanks for the links I read both threads and they were helpful. Id still like to see dyno comparisons for small bore 346's to better help me decide. Ill most likely go with the 1 7/8" after a little more research.

no prob...if you find some more good links post them up!