[Umbriel]

Originally Posted by 18ss376

If your not planing on making over 800hp you will be leaving h.p. on the table with a 2" primary header. If over 800hp then yes a 2" is the way to go.

Only thing you would be leaving on the table with 2 inch over 1 7/8 might be some low end torque, you aren't going to lose hp with a bigger primary.

With that being said I have the 2 inch TSP headers and they fit perfectly fine and I was able to get a Rotofab, E85 kit and tuning with the money I saved.

[oldman]

I'm on the 1 and 7/8 camp, the fitment, heat, and spark plug wire burning issues. I still have the OEM wires, can't say that on ANY 2". I did cook my starter so heat wrap of both the starter and two header tubes is a must no matter the header.. even OEM bone stock have starter cooking issues in Texas.

Drivability with M6 1 and 7/8 with cats is almost OEM. I think M6 with 2" and no cats will really have issues being a DD, (no low end torque as in zero).

[Baker]

Originally Posted by JCurry2885

I deleted the rear o2 sensors so it would have had a CEL. We tuned it with HPtuners after the install, no issues after the tune.

You already got yours? I ordered mine too and they haven’t shipped yet

[18ss376]

Originally Posted by Umbriel

Only thing you would be leaving on the table with 2 inch over 1 7/8 might be some low end torque, you aren't going to lose hp with a bigger primary.

With that being said I have the 2 inch TSP headers and they fit perfectly fine and I was able to get a Rotofab, E85 kit and tuning with the money I saved.

I have proof, do you?
I have been dynoing engines since 1987, the avg. loss is 15h.p. I have a lot of dyno sheets that prove this on different CI of SBC engines. Feel free to stop by & I'll put a LT1 on the dyno & prove that 2" primaries LOSE h.p. over 1-7/8"

[oldman]

there have been dynos out, as a surprise there does not seem much loss for the 2" header on the low end, not much gain on the top end. Of course this is WOT. For 99.99% of the people I think the 1 and 7/8 will be enough. Only on max build NA or FI above 700 WHP could I see the 2" with a no cat 3" exhaust system. Below that it is bench racing and matters little IMO, given this the 1 and 7/8 just has less draw backs. For an M6 I recommend only a 1 and 7/8 with cats for all builds period.

[18ss376]

I also use software called "PipeMax" to design headers it is very accurate.
http://maxracesoftware.com/PipeMaxPro400.htm

[Umbriel]

Originally Posted by 18ss376

I have proof, do you?
I have been dynoing engines since 1987, the avg. loss is 15h.p. I have a lot of dyno sheets that prove this on different CI of SBC engines. Feel free to stop by & I'll put a LT1 on the dyno & prove that 2" primaries LOSE h.p. over 1-7/8"

I can't stop by Oklahoma from Tennessee but you are more than welcome to show me somehow on here and I will gladly say I was wrong. In this article from Superchevy it states to use 2 inches or greater for 500+ hp. I am not saying 2 inches is better than 1 7/8 at 500 or less but I just don't believe you will lose hp using 2 inches over 1 7/8 just not gain anything.

http://www.superchevy.com/how-to/eng...t-performance/

Also Joe at CPR recommends 2 inch headers on the new LT motors, said the 2 inch headers made more hp and tq across the rpm band.

Originally Posted by Joe@CPR

ARH is the preferred brand here, we have installed 5 now and the fit and finish is perfect. 2'' is also the better option on the new LT motors. We make C7 longtubes and during our testing tried all 3 of the popular sizes and the 2'' made more hp/tq all across the rpm band so we decided to only do a 2''.

Here back to back testing it says the 1 7/8 was better down low but the 2 inch did make more at 6000+ so the 2 inch still made more power.

https://www.camaro6.com/forums/showthread.php?t=472259

Here 2 basically identical cars were tested and the 2 inch headers made more also.

https://www.facebook.com/prayperform...type=3&theater

[oldman]

There have been more than a few dyno between 2" and 1 7/8" we're beating a dead horse. My issue is with fitment vs any small gain, and yes actual drivability, which favors the 1 and 7/8. I'd have to see 20 WHP gain by going to 2" due to the fitment problems and that ain't going to happen at my 709 WHP target, but assume 1000 WHP builds would see something like that.

IMO 99% of the people will be happy with 1 and 7/8. but would agree there is a few HP on the top end FBO with 2" and probably more max DD effort NA, max DD effort FI. Depending on how you define DD, I'm sure we all have 1000 WHP DD right.

[Umbriel]

Originally Posted by Umbriel

I can't stop by Oklahoma from Tennessee but you are more than welcome to show me somehow on here and I will gladly say I was wrong. In this article from Superchevy it states to use 2 inches or greater for 500+ hp. I am not saying 2 inches is better than 1 7/8 at 500 or less but I just don't believe you will lose hp using 2 inches over 1 7/8 just not gain anything.

http://www.superchevy.com/how-to/eng...t-performance/

Also Joe at CPR recommends 2 inch headers on the new LT motors, said the 2 inch headers made more hp and tq across the rpm band.




Here back to back testing it says the 1 7/8 was better down low but the 2 inch did make more at 6000+ so the 2 inch still made more power.

https://www.camaro6.com/forums/showthread.php?t=472259

Here 2 basically identical cars were tested and the 2 inch headers made more also.

https://www.facebook.com/prayperform...type=3&theater

FRANKENSTEIN ENGINE DYNAMICS from this forum:

Originally Posted by 62nalide

We have been making 8whp 3wtq more vs the 1 7/8s......these LT1s like the bigger headers. We will not sell nor install any 1 7/8s at our place.

[Umbriel]

Don't know why it quoted all of my post.

[18ss376]

This is not as good as PipeMax but it's free.
http://www.wallaceracing.com/header_length.php

Also: https://www.yellowbullet.com/forum/f...splay.php?f=14
There are professional engine builders on this website & they know exactly what will work.

[18ss376]

Just ran the numbers on my PipeMax software it says 1.71" primary max...LOL

[Umbriel]

Real world results > software results. I'll stick with 2 inch headers.

[18ss376]

I do my homework before I listen to anyone.
The dyno & software are just tuning tools.

Real world results = a time slip form the drag strip!