flow master merge will help but will never flow as well as x pipe and duals. Probably a difference of 10-15 horses.

 

Damn. I'm looking to do a similar build. In the case of duals, would I then see much with a 2.5" pipe over 3"?

 

There was an exhaust flow chart somebody posted. I want to say 2.5" duals flowed with almost no loss at the 450 mark, but not 100% sure.

Also I just saw an older thread where someone posted 12 horsepower difference between a 3" cat back and open cutouts on their 4xx horsepower car. Hope that helps

 

2.5 duals aren't losing anything at 450. The 5th gen guys report no difference between the 2 up to 600 whp

 

Not sure if your interested but I am selling my old setup to move onto my 408 turbo build. My heads and cam will be for sale soon aswell as my ls1 alum block 6.125 scat h beams and mahle forged lightweight Pistons. I'm re using my crank for my new build. I made 459 to the tire at 22 degrees of timing on 93 octane. I'll also won't be needing my injectors either they are the red top 36 pound injectors. I'm just now disassembling the old block and can send you some pics of the rotating assembly if you would like. They still look new.

 

Also have tsp 1 7/8 headers with Borla full exhaust listed in the parts classified now and soon will have the rest listed

 

I ran fast 92 ported by vengeance aswell as the ported 92 throttle body that I'm going to reuse.

 

I made that power with my 383 through a th400 and a 12 bolt mossier reared and have a pic of the dyno sheet

 

my buddies car MS4 Ported ls6 heads ls6 intake and 1 7/8 longtubes custom mandrel y pipe with flowmaser merge and a sinister 4" catback made 460rwhp the exhaust was worth 30hp over an slp header y pipe and loudmouth combo

 

I don't have a Flowmaster merge but I do have a single pipe. I think it does just fine with my setup. In my opinion, until you reach a certain amount of horse power the difference between a good Y pipe setup and a good X pipe setup will be little to none. The reason I chose the exhaust setup that I did was the weight factor.

 

@Poltergeist If i'm reading your sig correctly, you're running a 4" pipe after the y, that's dumped before the axles?

I was thinking of going with a good y, and doing a cutout instead of TDs. Seems to me to be much cheaper. Opinions on that?

 

If you have a 3" Y pipe to start with, it can be cheaper. The vibrant merge was $100, I think the vibrant muffler was about the same, then I used a 4" stainless diesel stack for the rest of the piping and turndown which cost $40 (ebay). I chose the vibrant merge over the Flowmaster cause it is stainless as well and the construction of this piece is really nice. The ONLY down side of doing this is it's loud. I have had multiple exhaust setups (pacesetter Y with hooker cat back, pacesetter Y with 3.5" mufflex, custom 2.5" duals with an H pipe out the back, custom 3" duals with an X pipe out the back) and the setup I have now. For a lower horse power car like mine I feel the custom single 4" setup is superior to the rest for MY application. Not only is it lighter but I would bet at this power level it would be within 2hp of a decent dumped X pipe setup on my car. Here is what most people don't realize, the area of a 2.5" pipe is 4.9087385212341, the area of a 3" pipe is 7.068583470577 and the area of a 4" pipe is 12.566370614359.

 

I've thought about ditching my CB as well since my car is no longer a DD

 

I've read that you "shouldn't" use stock rockers with AFR heads because it would cause premature wear on the valve guides. This is the only thing shying me away from AFRs or other heads with bronze guides. I have similar goals as the OP. I already had CHE upgrade my stock rockers as I had planned to go with a ported LS6 head so I could keep stock like reliability and longevity.

 

Hmmm. I guess I should probably mention that (after a brief discussion with Tony) I'm going with his new MMS 220's. Though I'm sure that's the same thing. I did just buy a set of rockers with the trunion upgrade already installed... I'll ask Tony. Worst case scenario is I turn around an sell them.

Thanks!

 

Tony will definitely want you to go with YT's.

You and I are going to end up with very similar rides, it looks like. I just made the same decision. I'm pretty much going all in for an optimized build so I know I haven't left anything on the table. good luck with your build. It'll be interesting to compare numbers.

 

I gained 19 RWHP and 17 Ft-lbs going from a catted LPP y-pipe and Magnaflow CB to a Kooks 3" catted True Dual kit.

This was with stock 243's, 227/235 cam and a FAST 102. Not that wild of a combo and quite a bit of a gain. Dyno sheets in the link:

https://ls1tech.com/forums/dynamomet...stage-2-a.html

 

I had a feeling. Oh well, guess I'll sell the rockers and get the YT's.

And hey, once we get our builds done, we'll have to run against one another. I think my gf has some family in AZ, so we might go on a road trip.

 

That would be awesome! What is the rest of your build going to look like? I'll be going pretty much by Tony's letter, other than the cam I have is close enough to the cam he would spec, so I'm leaving it in, and I don't have true duals, and I have a heavy clutch.

But, the heads are the foundation. Once they're done, everything else is relatively easy. Down the road, I'll throw a set of duals on and go with a carbon twin disc, which will make a difference.

 

TSP 1 7/8 headers
TSP off road race Y pipe
Borla cat back wide open exhaust
All looking for a new ride to make scream
I want 800 for everything you see here
Value of close to 1800