When are 2" headers necessary?

[MarylandSpeed]

Originally Posted by Kilo-9

Maryland Speed, any chance we will see the 1 7/8-2" stepped Signature Series readily available from Kooks or are they going to be special order only?

I am not a fan of this set up..and here is why. For a stepped header to work, it has to be sized right. I don't know the exact measurement of the exhaust port on the LS3 head..but it is less than 1 3/4". So when you run say a straight 1 7/8" or 2" header..the exhaust is coming out the head, and immediatly dumping in a header primary that has a bigger diameter. The 1 3/4" by 1 7/8" header we sell is just right for 95% of the cars out there because the smaller 1 3/4" initial primary is much closer in size to the exhaust port, which keeps the exhaust pressurized. It is not dumping immediatly into a much bigger 1 7/8" primary. Going back to the garden hose..the 1 3/4" section of our current stepped header is like slightly pinching the garden hose..it accelerates the exhaust gas..and then the rest is 1 7/8" to allow more total volume to be moved through the header. With 1 7/8" stepped to 2", this advantage is lost because honestly..1 7/8" is slightly big for these cars as it is, and does not create the higher pressure that a 1 3/4" first section does. If you go on Corvette forums for instance..most bolt on LS3 guys run 1 3/4".

Now of course if you are up around 700 rwhp and have ported heads, then 1 7/8" stepped to 2" may make sense. It is all about having the right header for the application. I have the 1 3/4" stepped to 1 7/8" Kooks on my Camaro witha TVS2300, and most people here would think that is crazy talk, and way too small. However the car makes 638 RWHP on a very simple build..which is in line with, or better than most similar builds I see.

Also FWIW on a 1 3/4" stepped to 1 7/8" header, the 1 3/4" length of primary is less than a 3rd the total length of the primary..so it is still for the most part a 1 7/8" header. It just has a small 1 3/4" section to pressurize the exhaust and get it going.

[MarylandSpeed]

Originally Posted by DietCoke

Not because it made more power (anywhere). Case in point.

Saying the 2" only makes significant gains over 4500rpm only furthers that its a superior choice. Do we race below that? Dur.

You do realize that the margin of error is greater than the 2HP difference on a dyno. And most people have their engine above 4500 RPM less than 5% of the engine life. I would say more people are concerned with low end TQ. Additionally there are tuning issues..putting a bigger header on a car than is necessary will decrease the exhaust flow efficiancy which really should be addressed in the tune. If changing the headers made the car run lean or rich vs. the last header tested..that can have a big effect on numbers.


But hey..I have only sold a few hundred headers here..built two of my own Camaro's...worked on customers cars, and so forth. What does my opinion, or the manufactuers opinion, or pretty much every LSX tech forum's commonly held opinion matter when there is a dyno sheet showing they make 2HP more at 5500RPM or whatever.

But again..I think a dyno test is in order..I will talk with Kooks tomorrow about getting some headers in. And as my ebay header thread showed back in the day..I don't cook the books..if the peak numbers are the same..I will post it.

[Inferno LSX]

Well then when will 2 1/8" primaries come out? That has to be better than 2". Lol

[CC Performance]

I run 2 " with 3.5 collectors.. BUT I also have 457 cubic inches as well
Its efficiency that your after.. there is a scavenging effect that takes place that actually helps to make better low and mid range..

[blazzin1]

Originally Posted by Inferno LS3

Well then when will 2 1/8" primaries come out? That has to be better than 2". Lol

Actually.....Big Flow Exhaust says on their website they have 2-1/8" headers "coming soon". However, it has said that for a long time now. Not saying they're better or anything, but yes, they may be available soon.

[Bell040]

from: http://www.camaro5.com/forums/showthread.php?t=63640

[Juiced1]

Originally Posted by jasycz28

I guess I should of said that I am whippled and at 570rwhp stock everything else. Next step in my plan is full exhaust and cai. Then a cam. So I hope to break the 700 mark. Really looking at LG's full setup nocats $1900 shipped. Might have to wait for a 2" special to happen.

I would recomend a 2" system for your set up. Go with ARH CA20102NC. That is their 2" long tube system with off road pipes and a full 3" X-pipe that connects to the axleback. This is one killer set up, give us a call.

[Anthony @ LG Motorsports]

I'm going to say 2" is to big as well.....and this is why.

Now we have done testing on Camaro's and Corvette's now and building our own headers for these cars for a long long time now.

From what we have seen on the LS2/LS3 cars in some cases a 1 3/4" would be better, but for the most part with the Camaro the 1 7/8" just due to the design of the header really didn't hurt anything. However going to a 2" did. Of course some of this plays into the full setup of the car and what you are going to do with it.

Someone said earlier that the 2" header made more PEAK HP, and it might. As for it over laying the bottom 3/4" of the RPM curve, I do not see that, nor I have I seen that on our own testing or testing of other companies headers. There was way to much of a drop in low and mid RPM hp to even consider doing that large of a header.

Remember we are working with less than 400 cubic inches and under 6500 RPM here. If it was a 9000 RPM engine...maybe. For example our 2003 Corvette TransAm series car used a 5.0L small block that would turn 8500-8800 RPM, and it used a big primary header on it, but the car didn't really even come alive until 4700-5000 RPM. Heads, intake, and camshaft were all built around this. So it is more than just the header, it is everything all wrapped into one, total package here.

With that being said, so far the 1 7/8" has proven the best setup for the car to date and we have stock displacement engines making over 560 rwhp using them. We will be working on a larger set for big cube engines and high boost applications.

[SGOS252382]

Time for another header test.
Not saying Jannetty's results don't speak for themselves, but many factors can affect test results.

Results of testing/experiments are not valid unless they are repeatable and replicable (done by others). One test is a start, but not enough to confirm something as being true or not true.

So bring on another header test. The more testing the better.

[FTI-EDC]

Originally Posted by Anthony @ LG Motorsports

I'm going to say 2" is to big as well.....and this is why.

Now we have done testing on Camaro's and Corvette's now and building our own headers for these cars for a long long time now.

From what we have seen on the LS2/LS3 cars in some cases a 1 3/4" would be better, but for the most part with the Camaro the 1 7/8" just due to the design of the header really didn't hurt anything. However going to a 2" did. Of course some of this plays into the full setup of the car and what you are going to do with it.

Someone said earlier that the 2" header made more PEAK HP, and it might. As for it over laying the bottom 3/4" of the RPM curve, I do not see that, nor I have I seen that on our own testing or testing of other companies headers. There was way to much of a drop in low and mid RPM hp to even consider doing that large of a header.

Remember we are working with less than 400 cubic inches and under 6500 RPM here. If it was a 9000 RPM engine...maybe. For example our 2003 Corvette TransAm series car used a 5.0L small block that would turn 8500-8800 RPM, and it used a big primary header on it, but the car didn't really even come alive until 4700-5000 RPM. Heads, intake, and camshaft were all built around this. So it is more than just the header, it is everything all wrapped into one, total package here.

With that being said, so far the 1 7/8" has proven the best setup for the car to date and we have stock displacement engines making over 560 rwhp using them. We will be working on a larger set for big cube engines and high boost applications.

Come on Anthony - What does "real world" racing results have to do with the internet?

Ed

[wylde1]

I shold preface my post by saying I'm not an expert, and only a hobbyist. That said, I've always been of the impression that you should match your primaries as close as possible to the size of the exhaust ports on your cylinder head. Pressure and velocity are inversely proportional, so evacuating into a larger pipe increases the pressure and decreases the gas velocity. The thing is though, sometimes the benefits of being able to extract more volume outweighs the benefits of higher velocity. So only going 1/8" diameter larger than your exhaust ports may help more than hinder, but going 1/4" may be the point where the higher pressure becomes counter productive since the stock motor might not be as efficient at overcoming it.

With high hp numbers and/or forced induction you are running higher cylinder pressures, which helps to overcome the expansion in the headers/exhaust, so you see better returns with bigger primaries even though you may not change the exhaust port size.

IMHO the primary is for extracting exhaust at the highest possible/most efficient velocity, and then the rest of your exhaust is for extracting volume.

[siriusdish]

2" Extra Drag racing power!!!!

[Chris@SPMC]

Here's my real world results from my personal car that is only 346ci and has a tiny 218* cam in it. Yes it traded some low end for top end, but when racing 5-7k rpm power is what counts and the dyno gains showed at the track as well.
http://forums.corvetteforum.com/perf...s-results.html

Here is another switch again of the headers only from the same manufacturer. This was a 395ci motor with a much bigger cam, still only a 3.9" bore unlike the LS3 that has a 4.03" bore. Not saying that bigger is always better, but heck 396ci big block chevys run 2.125" primaries.

[wylde1]

This is a very interesting read.

http://www.rbracing-rsr.com/exhausttech.htm

It's mostly about motorcycle exhaust design, but the principles are the same.