Big Block 7.4 Exhaust

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TexasAggie

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Howdy folks - Finally found a set of headers for my '99 K2500 Suburban. I'm trying to decide how to run the exhaust now... I've read quite a few posts, but can't find exactly what I'm looking for. I'm planning to have everything new... high flow cats, flowmaster (probably 40 series) mufflers and an x-pipe. EGR will be deleted since the headers don't have the port to utilize with the EGR pipe. Thinking of running the pipes straight out the back (period correct for the 1990s) or out behind each tire.

What size pipe should I run? Motor is stock and will likely stay that way. If/when I rebuild it, it will be more power, but nothing crazy. I'm not looking for anything super loud, but want a nice deep aggressive tone. I'll have the pcm programmed by Black Bear when it's all installed in order to maximize any performance gains.

Thoughts on how to run these pipes?
 

HotWheelsBurban

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Howdy folks - Finally found a set of headers for my '99 K2500 Suburban. I'm trying to decide how to run the exhaust now... I've read quite a few posts, but can't find exactly what I'm looking for. I'm planning to have everything new... high flow cats, flowmaster (probably 40 series) mufflers and an x-pipe. EGR will be deleted since the headers don't have the port to utilize with the EGR pipe. Thinking of running the pipes straight out the back (period correct for the 1990s) or out behind each tire.

What size pipe should I run? Motor is stock and will likely stay that way. If/when I rebuild it, it will be more power, but nothing crazy. I'm not looking for anything super loud, but want a nice deep aggressive tone. I'll have the pcm programmed by Black Bear when it's all installed in order to maximize any performance gains.

Thoughts on how to run these pipes?
One thing I will say about straight out the back: it looks great but not so good when you're hooking up or unhooking a trailer with the truck running. When I get around to having tailpipes put on the crew cab(gonna be a while cause the muffler replacement is much higher priority) they'll go out the corners like the square body trucks did...for that reason. We had the straight backs on our '78 GMC Sierra after Dad and I put the headers on and dualed it out. Looked cool as anything except for trailering.
 

TexasAggie

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Yeah, that is one thing I've considered. I'd also have to move my trailer plug (it's mounted to the side of the hitch right now). I like the look because it is how they all looked back then, but probably going to go out the side.
 

Piratehunter

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Also meant to ask, is the EGR block off plate the same on the 7.4 as it is on the 5.7?
the intake manifold plug is adp5406-p-12 12mm-plug, plugs the egr tube hole, you may not choose to use this plug, it will keep the port clear in case you go back to the transfer tube, the egr cover plate is GM 12554606. https://www.ebay.com/itm/313388933506

to get leverage on the manifold connection couplers I used a crowfoot I found on Amazon that let me add some leverage over wrenches.

Sunex 97760A 1/2" Dr. 1-3/8" Jumbo Crowfoot Wrench


The transfer tube is a valuable piece, don't throw it away.
 
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TexasAggie

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I've seen a post or two about adding the port for the EGR tube... any advantage to keeping it? I'll definitely hold on to the tube itself.

Any thoughts on pipe size?
 

b454rat

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I ran 2 1/2" duals on a 97 I had with the 454. At first it went straight out the back, then the pipes rusted it out, then had them on an angle out the back, came out underneath the taillights. 4" polished tips, looked good, sounded awesome. If I didn't have a couple sets of tail pipes I'd prolly run em again that way.
 

454cid

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I've seen a post or two about adding the port for the EGR tube... any advantage to keeping it? I'll definitely hold on to the tube itself.

Any thoughts on pipe size?

I don't think you can just disconnect EGR without tuning it out of the PCM.

Stock pipe size is about 3" at the head pipes, but squished a bit. Then it tapers down to 2.75" I think at the convetors, and comes out of the muffler as one pipe, but I don't recall the diameter. I think I'd be tempted to keep a 2 into 1 setup, but maybe run 3" pipe the whole way. I have no technical theories behind that idea, Though. My truck is basically stock.
 
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