Just thought I share some pics of My 5.3 "Off road" pipe compared to cat pipes off a 6.0 1500.
The Y-pipe isn't squished like the 6.0l???

 

Is that a question or some crazy statement?

The 1/2 ton 6L trucks (SS, Densli, Escalade, etc...) have the same crimped 2.5" cat pipe, but it just doesn't go into a Y, it stays dual. The HD trucks have a larger pupe and larger cats. They stay dual as well, but the cat are further back in the exhaust. I wish my truck came with HD pipes and cats.

 

What I meant was
The factory y-pipe on My 2wd 99 step side was not crimped. Although every other year Truck, (Including my 03 Sierra) That I have seen is crimped or squished. Maybe I just got lucky with the 99.
I just was posting pics of the two pipes I have next to each other.
The 99 5.3 y-pipe VS the 6.0L SS cat pipes I just got.
The only modification I did to the 99 pipe was eliminated the cats and welded flanges for the long tubes.


Just posting info,
I'm in the process of installing a complete dual 6.0l system on my 5.3 Z71.
Hopefulluy I'll have a 6.0l in it soon so I'll be ready with the exhaust.

I can't seem to modify My Cardomian site so I don't know why the pics arn't working.

I'll try again.

 

is the squished part the part that goes under the tranny? if so i think theres 2 designs on the pipes. i think it depends if you have a deep pan or a shallow pan. not sure. it could also be that GM changed venders after 99 and the new people made it with the flat spot. my 99 also does not have the flat spot.

 

So you're getting away with that mod in NY with upcoming emission testings? Just curious if you know something more than I do as I would like to get a 6.0 and exhaust in there in the next year or so.

Andrew

 

Emission testing doesn't exist in the boonies.
I'm sure the GMC will still pass. The cats are the same size as the 5.3.


As far as my race pipe on my 99 the local dealer told me as long as it doen't throw a code, ( like bad cat) it won't fail. At least that is the sytem there using,
I believe that is the extent of the emission testing in upstate NY.
I'll deal with the rest if it gets worse than that.

 

Ahh, ok, I was told emissions is looking for stock emissions equipment and any deviation from that. I was a little worried about headers and non 4.8 exhaust when I start doing the 6.0. All good. Sorry for the hijack.

Andrew

 

I got the 6.0l manifolds today and I thought I'd share some pics of the differance between the 5.3 and 6.0.
The 5.3 and 6.0 "driver" side manifolds are almost the saem except the outlet on the 6.0 is slightly larger but
The pasenger sides differ at the collector flange. The 5.3 has a donut/floating flange and the 6.0 has the fixed flange like the drivers side.
here's a pic of the 5.3 pas side VS the 6.0 Pas side;

The 5.3 lines up with the 6.0 catpipe but don't know how ell it would seal,

Heres the two side by side, The 6.0 being on top

 

Did one of the manifolds look like it had a smaller outlet size than the other? Mine did.

 

Yes I measured them all and took some pics.
6.0 Driver side outlet approx 2 1/2 ID
6.0 Pasenger side outlet approx 2 3/16 ID

5.3 Driver side outlet approx 2 3/16 ID
5.3 Pasenger side outlet approx 2 3/16 ID with donut

give or take a C hair

The casting look the same after I took the heat shields off with the excepting the 5.3 has egr.

The 1st pic is the DS 6.0
The 2nd PS 6.0
The 3rd DS 5.3
The 4th PS 5.3
The last is the 6.0 vs 53 pas manifolds