Headers

[MidnightSS]

Just probing to see if anyone has changed to headers. I had a ZR2 that I had changed to headers (along with plenty of other mods) and it made it sound great. I already had an appt. to have flowmasters and a custom true 2-1/2" dual exhaust a couple of days later, but the "pulse" sound was very noticeable even before the rest of the exhaust. I think that even with the stock muffler, a MUCH better sound can be had with headers. From the research I have done, the Gibson Performance GP500S will fit because they cross reference with the same exhaust manifolds that are on the '03 Hummer, 03 Denali, and 03 Escalade w/ 6.0L. I also think that they help even more if you have supercharged, as dcairns has.

By the way, I've been reading these posts for months, just never felt the need to jump in until now. I traded my 02 8.1L Allison Crew Cab 2500HD in for one and am not disappointed one bit! That truck with the hypertech and K&N FIPK was an awesome truck in its own right, but this thing handles so much better, especially in the rain! I think the SS has great potential, as there are a few things I will change, and a (probably wishful thinking) supercharger in its future.

[Extreme4x4]

Has anyone done actual dyno tests of headers or aftermarket exhaust on the 345hp 6.0????

 

The reason I ask is that many of the newer vehicles exhausts are pretty darn efficient. I would just be curious about cost effective hp.

 

On the Lightnings, spending $1800 on a full exhaust including headers will give about 10 whole hp. Basically, you are spending alot of money to make it sound better.

 

Also, exhaust will not necessarily benefit a supercharged engine. Freeing up the air flow will lower your boost (which is a byproduct of back pressure). Thus you flow more air but get less boost. Until you reach a point where your exhaust or intake is actually a detriment to boost, freeing it up will produce little extra power (some, but not enough to make it worth the money). With the Lightning, it isn't until you change to the Kenne Bell blower. Then the exhaust is finally worth some hp.

[dcairns]

I agree with you Extreme4x4. I think the stock exhaust system is pretty good. Have you taken a look underneath? Those are some healthy diameter pipes. Any improvements are going to be small, and be at the cost of more noise (sometimes a good thing ). I prefer the stock exhaust sound. Sounds healthy but not so loud as to announce your presence to all the local police Besides, the sleeper thing is fun. Beating some loud, lumpy idling thing and making it look effortless, is my kind of fun

[johnsen]

i like mine loud, so headers and mufflers are a must for me!

[BigTex]

All Gen III truck engines have the same exhaust manifolds. I installed a set of mid-length headers on my 99 Z71 and saw a 20 HP / 20 TQ gain. I think the LQ9 would respone even better to a good exhaust.

 

I put a set of full length headers on a Cadillac Escalade EXT. The exhaust made a huge difference in how it felt. Besides the headers, it had full 3" mandrel bent exchaust with an X pipe and dual magnaflow mufflers. The exhaust was worth it.

 

I have a set of Arizona Speed Marine long tube headers sitting right here waiting for an SS to come along. Too bad I can't dyno the before and after results.

 

One other thing - Is the muffler the same one that GM uses on the other 6L motors? Dual in - Dual out. If so, only one of the out pipes are functional, the other out pipe comes out of a closed up chamber in the muffler. So all exhaust is coming out of the single pipe. Someone needs to cut the SS muffler open to find out.

[MidnightSS]

I wasn't really talking about the exhaust as a whole being replaced. I know the pipes are good as well as being dual all the way back to the muffler. I was only talking about the exhaust manifolds being replaced with headers. They are your standard stock- dump into the same inline pipe. Yes, THESE CAN BE IMPROVED! Has anyone looked at them?

[MidnightSS]

By the way, boost is a product of back pressure, but this is the back pressure going into the motor, not exhaust back pressure. Some intake improvements such as a larger throttle body and larger valves will lower boost, wich means that you can crank the boost back up to the previous number without problems, showing the real gains in hp. Exhaust back pressure just robs horsepower having to push the exhaust through a restriction.

[BigTex]

I wasn't really talking about the exhaust as a whole being replaced. I know the pipes are good as well as being dual all the way back to the muffler. I was only talking about the exhaust manifolds being replaced with headers. They are your standard stock- dump into the same inline pipe. Yes, THESE CAN BE IMPROVED! Has anyone looked at them?

Well, thats what I was referring to in my previous post. My 20 / 20 gain was with just a header swap using the existing factory pipes the rest of the way out.

 

Yes, I've looked at them. The manifolds are the same on all GEN III trucks, so they have been out for 5 years.

 

On the stock pipes, take a look at them, they suck. They are basically the same pipes after the manifold that comes on the 4.8 and 5.3 trucks with the exception that they go directly into the muffler instead of into a Y-pipe. They are the same diameter (2.5") have the same exact bends, cats, and bung locations. Take a look the the nice "crimped" pipe job GM did the the drivers side pipe as it crosses under the transmission and tell me they are good.

 

Several manufacturers make long or mid length headers for these trucks. Dont waste your money on shorty headers.

[MidnightSS]

I agree with you BigTex on the crimp. I forgot about that. The Y-Pipe from my stock setup from my ZR2 sitting in my garage is HORRIBLY crimped! The pipes (being stainless and not too bad on the diameter (looks 2 1/2" or 2 1/4"???) don't look like they would be the first thing on my list to replace. Anyway, my response wasn't really to your reply, seeing as you agree that there can be some improvement with headers. Also, dcairns they didn't make the ZR2 much louder at all (Same with the Mustangs). It just gave it a nice pulsing sound. I have had a few Mustangs and they came with headers from the factory (all 4 tubes dumping into a common collector). This helped give them that good sound stock, but remained quiet. Anyway, this is a good forum. Keep up the good work!

[zippy]

i agree with you about the headers, as any guy with an f-body if going to headers helped him. one hell of a difference. the manifolds only very slightly between gen III engines and the truck manifolds certainly aren't great. as for the cat back, it certainly can be improved apon. big pipes does not mean good flow if the muffler sucks. look under a 2500hd and you'll see where they came up with this throaty nascar sounding system (i personally liked the hd sound better). aside from the muffler itself weighing in at more than some complete systems, it doesn't flow well.