getting new exhaust system, need advice on headers

[Scooterwrench]

+1 on headers. Long tubes make more lower end torque and in the real world that's what you want. You can do the fancy ceramic coating if you want,ain't gonna make 'em perform any better. Get yourself a set of Headmans and using a die grinder and rotary file and smooth out the welds inside where the tubes are welded to the flanges and up inside where the tubes are welded to the collectors. After you get them smoothed up inside either sandblast the "shipping paint" off or build a big fire in the backyard and throw them in to burn it off. Wire brush and scuff sand then paint with VHT high heat paint. The stuff a quite durable once you cure it with a few heat cycles. Throw the header gaskets in the trash and install them with exhaust manifold gaskets or use the all copper header gaskets. I have used manifold gaskets for years,they don't blow. Because the fuel tanks are on the left side of these trucks its kinda hard to balance your dual exhaust. My thought would be to run 2-1/2" pipes off the collector reducers and cross the left side over and both sides into a high flow muffler with two 2-1/2" inlets and one 3" outlet and run the exhaust out in the stock configuration. The dual inlet muffler creates your crossover.

 

[Schurkey]

Perhaps a moderator will move this thread into the Exhaust sub-section.

The catalyst(s) will have to stay in their OEM position(s) unless you can come up with an EPA or CARB exemption number for the new exhaust system.

 

[L31MaxExpress]

GM 350 Crate Engine Build - Chevy High Performance

Read the tech article on a GM Budget 350 Crate Engine Build, brought to you by the experts at Chevy High Performance Magazine.

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The 330 HP 350 Car Craft tested in 2004 had a pretty good torque bump as well.

GM 350 - Project Humble Pie - Tech - Car Craft Magazine

Read about this GM 350 H.O. project buildup from Car Craft Magazine

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[Erik the Awful]

When I first did my exhaust system on WCJr, I wanted manifolds because they're quieter, less prone to leaks, and keep the underhood temps down. Having gone with long tubes, I wouldn't spend a dime on manifolds. There are some manifolds that "suck less", but there aren't really any good ones in comparison to headers. Our engine bays are big and open enough that heat isn't an issue and Remflex gaskets eliminate the leaks.

 

[L31MaxExpress]

When I first did my exhaust system on WCJr, I wanted manifolds because they're quieter, less prone to leaks, and keep the underhood temps down. Having gone with long tubes, I wouldn't spend a dime on manifolds. There are some manifolds that "suck less", but there aren't really any good ones in comparison to headers. Our engine bays are big and open enough that heat isn't an issue and Remflex gaskets eliminate the leaks.

The Holley SBC manifolds are very nice and I know I am giving up a little power on the L31 I built for the 87 G20 van by using them. But I wanted to be able to drop that engine into the van, bolt it up and fire it up.

I bought a second pair of those manifolds. If the 383 ever has to come out of my 97 van, I am going to do the same manifolds on it. The headers definitely add power but they add add a tremendous amount of heat and have to be removed and installed in the tiny, cramped engine bay, where the manifolds can stay on the engine.

 

[GMTMark]

+1 on headers. Long tubes make more lower end torque and in the real world that's what you want. You can do the fancy ceramic coating if you want,ain't gonna make 'em perform any better. Get yourself a set of Headmans and using a die grinder and rotary file and smooth out the welds inside where the tubes are welded to the flanges and up inside where the tubes are welded to the collectors. After you get them smoothed up inside either sandblast the "shipping paint" off or build a big fire in the backyard and throw them in to burn it off. Wire brush and scuff sand then paint with VHT high heat paint. The stuff a quite durable once you cure it with a few heat cycles. Throw the header gaskets in the trash and install them with exhaust manifold gaskets or use the all copper header gaskets. I have used manifold gaskets for years,they don't blow. Because the fuel tanks are on the left side of these trucks its kinda hard to balance your dual exhaust. My thought would be to run 2-1/2" pipes off the collector reducers and cross the left side over and both sides into a high flow muffler with two 2-1/2" inlets and one 3" outlet and run the exhaust out in the stock configuration. The dual inlet muffler creates your crossover.

Now that’s the way to configure exhaust for these trucks. I’ll be doing the same with shorties but I want to easily swap back to manifolds if I want. I never can make up my mind so I decided to make it cheaper to change things. You shouldn’t need a Y-pipe with the 2-in muffler.

 

[Scooterwrench]

If you have the ability or know someone who does you can have a custom muffler made with a large front chamber. It acts like an expansion chamber that produces even more torque. An expansion chamber should have twice the cylinder volume.

 

[Kens1990K2500]

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.

When I bought my truck in 2020, it had a cracked exhaust manifold. I decided I didn't want to install another cast iron manifold, since the only options are used OEM, or aftermarket, and anyway, a replacement manifold could crack again.

I decided to go with shorty, stainless steel headers I bought off eBay for around $100. Actually, I was pleasantly surprised with the quality of the headers, which had a thick, straight flange, and no leaks whatsoever (I did use better quality header bolts). They looked beautiful right after I installed them, but they did discolor, since I didn't bother to have them coated. I did have to modify the power steering bracket, and had to bend the oil dipstick tube, which made it kind of difficult to insert the dipstick.

The headers were supposed to line up with a stock Y pipe (which is a major selling point of shorty headers, vs long tube headers), but they did not. I ended up having a custom exhaust made, from headers to tailpipe (which I'm glad I did, since the existing exhaust was cobbled together). Truck has a nice, deep rumble, not too loud. The truck seems to have picked up some torque. Overall, I'm happy.

 

[Kens1990K2500]

Now that’s the way to configure exhaust for these trucks. I’ll be doing the same with shorties but I want to easily swap back to manifolds if I want. I never can make up my mind so I decided to make it cheaper to change things. You shouldn’t need a Y-pipe with the 2-in muffler.

When I had my custom exhaust done, they went with a 2-inlet, one-outlet, muffler. I like it.