I have an 02 Suburban with 5.3 FF that I use for towing my karting trailer around. I'm looking to find a little more power out of it and have started with doing a Volant intake and am currently working on the exhaust. I've started with a Flo-Pro 2504 muffler that is dual 3" in and dual 2.5" out. It is supposed to flow much better than the stock muffler and is only slightly louder than stock which is what I was looking for. I am looking at doing the headers next and have been looking at the Speed Engineering long tubes in 1 3/4". My question is about the tubing from the headers to the muffler. Speed engineering sells a x-pipe kit that bolts right up to their headers but I'm concerned with losing torque going that big being N/A and only 5.3 so was thinking of making my own kit and reducing it down to 2.5" as to try and not lose down low torque. I would love to hear what others have done and what the results were. My next mod after this will be BTR truck norris cam, valve springs and a tune. All the reviews from the cam say if the exhaust is too big it seems to lose power under 2500 RPM which I would like to prevent. Thanks

 

I'd skip the headers and just do the camshaft upgrade. That way you will lose basically zero low end grunt.

Plus the headers without cats or many resonators will be super duper loud in the truck while towing. If you hate drone, you will hate it without cats and resonators.

 

Thanks for the reply. I was actually debating doing a set of high flow cats while I was doing everything else to help keep the sound at a tolerable level. Was just trying to find that little extra HP as the thing is a sled the way it is currently. The intake and better flowing muffler helped but it could still use a little more. I keep kicking myself for selling my diesel but it was only cab and a half so my daughter complained about leg room on long trips to further away races.

 

The other option is to re-gear the truck. But that can be more costly if you had a shop do it.

Going to 4.10's would make a hell of a difference if it had 3.42's or something.

 

It has 3.73 in it currently and doing 4.10's actually crossed my mind. I am about to rebuild the front diff as the bearings are noisy. I could do it all myself as I am a certified mechanic that used to specialize in rebuilding manual transmissions but just thought it would be a pain in the **** and was concerned with fuel economy. What's crazy is a friend of mine has a similar suburban to mine with 4.10's and he actually gets better fuel economy than I do. Doesn't really make sense to me. He turns almost 1000 rpm more than me on the highway.

 

Converter can stay locked longer, less energy lost trying to accelerate and probably spinning at an RPM closer to or even at 100% VE

I went from 3.73 to 4.10 and will be settling on 4.56 for my gear of choice

A small cam will really help. I have a 212/218 112LSA .550 lift, huge improvement. I have supporting mods, but went from 204whp to 302whp. I tow a lot with my Tahoe. Everything from trash to ***. haha jk. I have 18' and 23' car trailers; I mostly tow cars, usually about 7k lbs. Sometimes its 3rd gear matted to do 60mph, but I also start my journey at 5500' above sea level and it only goes up from there

I have built several exhausts for this truck, and used packed mufflers each time. I am getting loud again, so my next mufflers will likely be chambered. No cats, 1 7/8 LTs

 

So I ordered a set of XS power LT headers and Y pipe. I've read that they used to make the LPP headers and the fitment wasn't terrible. I figure I have a welder and know how to use it. I wasn't going to spend $2k on an experiment. I'm going to try them without a resonator at first and see how loud it is. If it' too tiney or loud I'm going to add a Moroso Spiral flow muffler. I used one on an old car I had it made the tone and volume much better. I thought about dynoing before and after but would have to take the front shaft out or dyno in 4wd.

 

I have LPP headers on my 05 RCSB 4x4 and they fit great after I beat them with a hammer. No, it wasn't sagging engine mounts because I have Atomic poly mounts.

They aren't bad other than knowing you will probably need to massage some stuff.

 

I managed to get the headers installed this weekend. What a nightmare of a job that was. I'm a professional mechanic and I hated it. Got the stock stuff out pretty easily. All was going well till the head fell off the drivers side rear most manifold bolt. Took almost 3 hours with a welder to get it out. There is not enough room to even fit a 90 deg drill in there. I knew of 2 other broken bolts but those came out fairly easily. Trying to get the passenger side header in was a bit of a task. I had to pretty much force it in past the heatshield for the rear hvac lines. Fitment isn't terrible but it isn't the greatest either. It took some finessing to get the crossover pipe to stop rubbing the front drive shaft. I think my engine mounts are worn as it is barely touching the frame rail on the passenger side. The driver's side dropped right in after unbolting the steering column. I towed the trailer with it this weekend and it definitely seems to require less pedal to get and keep it moving. I haven't done log yet. I need to reflash the ecm to turn off the rear o2 and cat monitoring. The exhaust surprisingly didn't get much louder. Definitely more throaty under full throttle but not terrible. I think I'll consider it good for now.

 

Yeah, the exhaust on our trucks can be a pain. LS's love to pop off manifold bolt heads too

Seems everyone has a horror story about that passenger side lol