Headers or iron manifolds?

[GrimsterGMC]

Good to know. I'm ordering ss header bolts/ should I do the same for the flange or just use the provided bolts and washers?

I am a bit hesitant when it comes to stainless hardware. While it is hard to cut, it is very malleable so I personally wouldn't trust the threads unless they where a specified grade for header bolts.

 

[SUBURBAN5]

I am a bit hesitant when it comes to stainless hardware. While it is hard to cut, it is very malleable so I personally wouldn't trust the threads unless they where a specified grade for header bolts.

They are. There from arp. But they don't provide hardware for the flange. I was just gonna roll the dice and use the hardware from the headers

 

[L31MaxExpress]

That's kinda like our '02 Q45, it had 3 cats, 2 mufflers, and 2 resonators

The 1st 2 cats were on the exhaust manifolds so, when the cats went out, you had to replace the manifolds too - up to $700 per! That didn't last very long, when it came time to get an emissions test, I junked the car since by then the PCM bricked.

I lucked out on my 2011 M56S when it needed cats. Was getting a catalytic converter code on it. Had the cats swapped while the engine was out for a timing chain recall. On the M56S to swap the manifold cats the engine and subframe get dropped.a

 

[Erik the Awful]

All the ones I have looked at were definitely not crush bent. 99 suburban, 99 Tahoe, the 97 van. They have all been mandrel bent and the ones I have had my eyes on were stainless as well. Stock Express van exhaust, always thought it was kind of goofy to have a resonator ahead of the passenger side cat. The Thorley headers 86'd that resonator. The resonator on one bank reminded me of the old Fords that had a catalytic converter on only one bank. Having those big pipes on the L31 is why I feel shorties made a big difference and ditching that chambered resonator is probably why my L31 loved the Thorley tri-ys.

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Those look like 2500/3500 pipes. My K1500 Suburban had the factory exhaust, and it was significantly smaller and restricted. I ditched the factory pipes, installed the 2500/3500 downpipes, and built the rest of the exhaust with larger mufflers and tubing.

 

[L31MaxExpress]

Those look like 2500/3500 pipes. My K1500 Suburban had the factory exhaust, and it was significantly smaller and restricted. I ditched the factory pipes, installed the 2500/3500 downpipes, and built the rest of the exhaust with larger mufflers and tubing.

Except GM loved the 2.75" pipes in the 2500/3500 trucks and those are a full 3" OD. Not that it makes a huge difference. I just always found it goofy that it had that huge resonator before the cat.

 

[Minn95Dually]

Since you don’t need an EGR port, check out the Holley cast manifolds. Look really nice and have good reviews overall. If they made a set with an EGR port, I’d have them on mine.

Wish they made them for big block.

 

[Sean Buick 76]

Long tube headers for sure and Remflex gaskets

 

[Schurkey]

Wish they made them for big block.

I bought--but have not installed--the cheap Dorman replacement exhaust manifolds intended for BBC in Corvette. They're nicely-shaped but poorly made. OTOH, I got a "steal of a deal" on them, even after sending them to the machine shop for resurfacing, they didn't cost me much.

Pretty sure I'll have to do "something" to get clearance to the 4WD oil filter adapter on the left side. Cautiously optimistic that they'll fit on the right side, but will need mods to the downpipe.

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www.amazon.com/gp/product/B00068OIYA/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Kens1990K2500]

I have used them the bolts are not the best but could be worse the gaskets are okay but you could get better. they do fit the factory y pipe and also should fit an after market one as well.

They're supposed to fit the factory Y pipe. Mine were off enough that I couldn't cheat 'em, and ended up taking it to an exhaust shop for a complete custom exhaust. Glad I did it, though.

 

[tykar3]

if you do not want shortys get ram horn manifolds way better then logs.

headers like this may be an option but I do not think you will gain any thing from them other than sound

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I have no firsthand experience with the new Holley/Hooker cast iron exhaust manifolds,
but they are getting good reviews, are supposed to flow better than stock,
you can still get to the plugs, and they have nice lines/easy on the eyes:

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Me? If I can't have a set of no-nonsense long-tube Tri-Y headers connected
to a quiet(er) high flow exhaust, I'll skip the shorties and go right for these
new performance-oriented cast iron manifolds. (I'll take the titanium-colored
ceramic coating - see attached.)

EDIT: I may have been misled elsewhere. The attached photos may be natural,
but I'd want the ceramic coating for rust free long-term + less heat radiated into
the engine bay. So I'll take the black ceramic over the natural.)

I'm too old to put myself through the header aggravation if they aren't going
to deliver enough additional performance to outweigh the extra effort.
Especially when using a stock/near stock cam where the difference between
a higher flowing cast iron exhaust vs. a shorty header just won't be there.

Will these actually fit a gmt400? I have a 1990 C1500, when I looked them up online it said they weren’t compatible, I obviously understand the downpipe will have to be changed, but I’m just talking about the manifold itself.

Also, I didn’t think Ramhorns would fit. I have a set of those but I have not tried putting them in yet.