getting new exhaust system, need advice on headers

[TommyJ1980]

Hello! 1998 K2500, 5.7L 250,000 miles, recent new head and intake manifold gasket installation. Turned my attention to the exhaust system, and the components aren't totally rotted out, but some parts of them are. Recently patched it up to keep it going, but now the donut between the passenger side exhaust manifold, and the down tube, has disintegrated. I have an appointment in the next couple weeks for a local muffler shop to replace the entire system from the manifold back, and install true duals. The shop will not do headers, and my future goals for this motor would be to install some bolt on mods, maybe a cam swap, and try to gain another 100 hp over stock, or so. At this point, I'm looking at installing the headers myself between now and the appointment for the rest of the exhaust system. It's a big learning curve, because I don't really know anything about this part of it, so I wanted to present it to the group, and ask for suggestions for the best headers to install for my vehicle, and see if there were any pitfalls. I understand that I might also need to do an EGR delete? Thanks in advance for any thoughts you may have on this.

Sincerely,

Tommy - Longview, WA

 

[Erik the Awful]

If you can do long tube headers, they will make more power than shorties. If you plan on keeping the headers for long, either pay up for ceramic coating or find a place locally that can strip and coat them for you. Note that ceramic coating does nearly nothing for heat control, but it keeps them looking shiny for years to come.

 

[2drXmobb]

Your in wa so no smog you can go long tubes, shorties give you a slight bump but not significant. Bigger pipes and a blower and cam with give you well over your goals .it's a lot of money to make things go fast . You might get 30hp with bolt ons probably 100 with a blower.

 

[2drXmobb]

If emissions wasn't a concern I did everything you could do to the l31s. Marine intake tune etc.

 

[pressureangle]

Hello! 1998 K2500, 5.7L 250,000 miles, recent new head and intake manifold gasket installation. Turned my attention to the exhaust system, and the components aren't totally rotted out, but some parts of them are. Recently patched it up to keep it going, but now the donut between the passenger side exhaust manifold, and the down tube, has disintegrated. I have an appointment in the next couple weeks for a local muffler shop to replace the entire system from the manifold back, and install true duals. The shop will not do headers, and my future goals for this motor would be to install some bolt on mods, maybe a cam swap, and try to gain another 100 hp over stock, or so. At this point, I'm looking at installing the headers myself between now and the appointment for the rest of the exhaust system. It's a big learning curve, because I don't really know anything about this part of it, so I wanted to present it to the group, and ask for suggestions for the best headers to install for my vehicle, and see if there were any pitfalls. I understand that I might also need to do an EGR delete? Thanks in advance for any thoughts you may have on this.

Sincerely,

Tommy - Longview, WA

Do a lot more homework and keep the iron manifolds. Stock manifolds and a flowmaster y-pipe give nearly nothing up to headers below 4500rpm.

 

[TommyJ1980]

If you can do long tube headers, they will make more power than shorties. If you plan on keeping the headers for long, either pay up for ceramic coating or find a place locally that can strip and coat them for you. Note that ceramic coating does nearly nothing for heat control, but it keeps them looking shiny for years to come.

Do a lot more homework and keep the iron manifolds. Stock manifolds and a flowmaster y-pipe give nearly nothing up to headers below 4500rpm.

That's the conclusion I've come to from talking to some people locally. I'm going to install new stock manifolds on both sides and take it to the shop to connect up to the rest of the new system. Gonna read up a bit more on the other options they gave me, Y-pipe vs true dual, etc, and you're right, need to do a lot more homework. It seems like everytime something else comes up on this vehicle, it's another area I know virtually nothing about...haha, that does change over time though. Appreciate the input.

 

[Komet]

Do a lot more homework and keep the iron manifolds. Stock manifolds and a flowmaster y-pipe give nearly nothing up to headers below 4500rpm.

On an otherwise stock application maybe, if 20+ ft lbs is nearly nothing to you.

EGR delete isn't totally necessary, just need a 3/4-16 bung welded in close to the stock location.

 

[L31MaxExpress]

Do a lot more homework and keep the iron manifolds. Stock manifolds and a flowmaster y-pipe give nearly nothing up to headers below 4500rpm.

Totally disagree! Headers make a HUGE difference in torque. So much so that on hills that previously required a downshift to 3rd to climb, my transmission would stay locked up in overdrive. A super basic small block typically gains 40-50 ft/lbs of torque from long tube or tri-y headers and most of that gain is in the low-midrange right where you use it.

 

[PlayingWithTBI]

The latest Engine Masters I watched showed how much headers help, shorty and LTs. It's more pronounced with modified engines but helps stock ones too. They used "Ram Horn" manifolds for their stock manifolds. Shorties added about 1/2 as much as LTs over stock.

 

[L31MaxExpress]

The latest Engine Masters I watched showed how much headers help, shorty and LTs. It's more pronounced with modified engines but helps stock ones too. They used "Ram Horn" manifolds for their stock manifolds. Shorties added about 1/2 as much as LTs over stock.

Back in about 2000 a 350 Goodwrench engine built to 70s smog era spec was tested on the dyno. Using a stock intake manifold, Q-Jet and 70s style 2" outlet stock under the plug style log manifolds. They then put 1-5/8" primary long tubes on it. The long tubes gained 53 ft/lbs @ 3,400 rpm. That is definitely noticeable.