Exhaust options for 6.0L swap

[Jeff7]

Hey guys, I'm going to be putting a 6.0L in my my 98 K1500 this summer and I'm trying to sort out the exhaust.

I'll be using stock manifolds, the guy building the engine said they flow great and I'm planning on a turbo in the future so dont want to waste money on headers.

My problem is what to do after that. Overall I want dual 3" pipe (looking at 400whp now and more with the turbo) with high flow cats, X pipe, and likely magnaflow muffler (DI/DO or 2 SI/SO, not sure yet). But because the money cats can get at recycling depots around here the stock down pipes with cats in them are crazy expensive, it's cheaper to put in my own cats. So I'm trying to figure out the best way to connect to the stock manifold and how to pipe it to the passenger side where everything will straighten out.

Any suggestions are appreciated, thanks!

 

[OutlawDrifter]

Dual 3" is overkill for a street driven 400rwhp rig....like way overkill.

Stick with dual 2.5", and honestly...I'd Y it into one 3" or 3.5" pipe. My 425rwhp 6.0L(LQ9 based) NA Z28 has 2.5" off the mid-length headers into a single 3". When I had a cutout in the y-pipe it was only worth 10hp, and that was with cross flow Aerochamber muffler. With my current Banks setup the cutout probably would make no difference.

A competent exhaust shop can make you down pipes for the stock manifolds. You can also cut off the factory flanges and weld on v-bands if you wanted(they are cast steel), I did this on my '49 GMC...this opens up lots of room for routing options. Pick the muffler/mufflers of your flavor and you should be set!

Any factory type downpipe setup would probably work with your pickup, Polarbear used a Jegs offroad factory fit Y on his LS swapped K2500 burb with factory truck manifolds.

 

[Frank Enstein]

I recommend the y pipe into the single 3" as well. When it's time for the hairdryer consider a rear mount turbo after the "Y".

Summit has the oil pumps for the rear mount turbo

 

[Jglew82]

Another 3”y pipe vote. I have long tubes on my 6.0 into a 3” Y, then into a SI DO 70 series Flowmaster.

 

[Jeff7]

Ok cool thanks for the input. Most of the online calculators were saying dual 3" would be good and a single 3" might leave something on the table so I didn't want to be cutting myself short.

This might actually work in my favour as far work goes, my stock 98 setup has a, self made cat back system of sorts, at the dual flange I have a 3" Y welded in to a SI/SO 3" magnaflow. So I could I just reuse all that and save myself some work.

I've heard of jegs off road pipes before but trying to avoid a Y that early, I need to fit in 2 cats to make it as good as factory. I honestly don't know what laws I need to follow as I'm military and bound to move provinces (Canadian) so I'd rather not shoot myself in the foot by not having 2 cats like stock and having registration issues down the line with a future posting.

And unfortunately I'm currently in Yellowknife where there isn't an exhaust shop, let alone a competent one, within probably like 800+ miles lol. So I'm building it all myself. But using a V band is a good idea. Could just get some 2.5" piping to make the down pipes myself and then some 2.5"-3" adapters and then into cats.

Can any of you 6.0L guys confirm 2.5" is the size I'd need to connect to 99-05 6.0L manifolds? I don't have my parts yet, I gotta make a 15hr drive to pick up the engine and all the parts I need from the wrecker at once so I don't have the manifolds yet just trying to get it all lined up.

Thanks again.

 

[OutlawDrifter]

2.5 will work just fine. You'll want 1-2 Mandrel U's to make the down pipes.

 

[Dropped88]

Ok cool thanks for the input. Most of the online calculators were saying dual 3" would be good and a single 3" might leave something on the table so I didn't want to be cutting myself short.

This might actually work in my favour as far work goes, my stock 98 setup has a, self made cat back system of sorts, at the dual flange I have a 3" Y welded in to a SI/SO 3" magnaflow. So I could I just reuse all that and save myself some work.

I've heard of jegs off road pipes before but trying to avoid a Y that early, I need to fit in 2 cats to make it as good as factory. I honestly don't know what laws I need to follow as I'm military and bound to move provinces (Canadian) so I'd rather not shoot myself in the foot by not having 2 cats like stock and having registration issues down the line with a future posting.

And unfortunately I'm currently in Yellowknife where there isn't an exhaust shop, let alone a competent one, within probably like 800+ miles lol. So I'm building it all myself. But using a V band is a good idea. Could just get some 2.5" piping to make the down pipes myself and then some 2.5"-3" adapters and then into cats.

Can any of you 6.0L guys confirm 2.5" is the size I'd need to connect to 99-05 6.0L manifolds? I don't have my parts yet, I gotta make a 15hr drive to pick up the engine and all the parts I need from the wrecker at once so I don't have the manifolds yet just trying to get it all lined up.

Thanks again.

Yes stock 6.0 Y pipe are 2.5. I just pulled trans at work out of a H2 hummer with 6.0

 

[Frank Enstein]

https://summitracing.com/parts/flo-y250300s

Will make your life easier. Orient the dual pipes vertically. Put the passenger side in the top and the crossover from the driver's side in the bottom. Much easier that way. I had Frank's done in about an hour.

 

[Jeff7]

Outlaw, any reason U's and not 90s? I haven't done any measurements yet but I figured it was just a combination of 90s to get the driver side over.

Dropped88, thanks for the confirmation.

Frank, this is just a regular Y right? I already have a Y (horizontal) after the cats, so I'll try to just make that one work.

What do you guys think about an X pipe? Would it be any benefit if it's right before a Y? I wanted one but I'm thinking if its that close it's not going to make a difference. Or I can try to fit it in before the cats...

 

[OutlawDrifter]

U's will give you more exact angles and allow you to route it specifically how you want. If you're going to do the 2-1, might get 3 U's just in case, never hurts to have more.

No X needed before the Y. Y does the same job.