High Mileage Twin Turbo 6.0 Build Part 2 – Exhaust Manifolds

In this installment we walk through the steps to create two turbo manifolds. All images from screenshots.

In this installment we walk through the steps to create two turbo manifolds. All images from screenshots.

Last week we brought you the details on a high mileage 6.0 powered GMC that Craig Poust is building, and documenting his install of twin turbos on. Today, we’ll take a look at the next phase of that project.

Step two in Craig’s voyage of adding twin turbos to the 2004 GMC 2500 HD he bought is to modify the exhaust manifolds for the T4 flanges and turbos. Craig doesn’t believe in buying new manifolds specifically designed for use with turbos because not everyone can afford to do that. There’s also the fact that for Craig there’s more satisfaction in modifying the existing manifolds than there is with buying ones specially made for this purpose.

Hit Up Summit or Jeg’s for the Pipes You’ll Need Throughout the Project

This part of the project will require some extra exhaust piping that we don’t always have sitting around. Craig gets one of Summit’s Universal Rod Builder Exhaust Kits for this. This is feasible for him because he does this quite a bit and he can use a single kit for a few builds and each kit comes with everything he needs to feed the turbo(s) he installs.

A universal exhaust installation kit like this one from Summit Racing is indispensable when installing turbos

A universal exhaust installation kit like this one from Summit Racing is indispensable when installing turbos

Jeg’s seems to want you to buy each piece of pipe that you’ll need individually instead of selling a kit with a good variety of lengths and bends. Doing it this way ensures that you don’t have extra pieces of pipe sitting around at the end of the build, but it does require you to design the turbo feed system prior to doing any work other than prepping the manifolds.

Whether you’re building a car up from a junkyard find or converting your existing car, Craig recommends hitting up ebay and getting yourself a decent little welder. Unless you plan on using it for more than just working on your car, you don’t need to buy an expensive or professional welder; according to Craig a simple 110volt unit will work.  If you’ve never welded before, practice even before tacking your pipes together. If you get the universal kit, you’ll have plenty of extra to work with.

Remove, Cut, and Flip or Flip Sides

Before we start this section, we need to mention that Craig normally reuses the metal exhaust gaskets unless they don’t come off nicely. He wouldn’t have been able to do this a few years ago because gaskets weren’t designed well enough to allow it. These days they are, so he does. He doesn’t even use copper gasket sealant, although you can if you wish.

Here we see two passenger side manifolds, with the manifold on the passenger side (L) flipped upside down and the exhaust flanges removed.

He starts out by getting the wiring and hoses out of his way and then carefully removing the manifolds and putting the manifold bolts in a tray or cup, one per side so he doesn’t mix the bolts up as to the side they came out of. This isn’t terribly important, but it is good practice.

The next step is to cut the exhaust pipe flange off the end of the manifold. “Every installation is different, even with the same year, make, and model,” Craig says. “So you will have to eyeball the manifolds and the engine compartment to determine where you want to make these cuts.” Craig also says you need to use your imagination so you can imagine where the turbo T4 flange(s) will go.

If, after eyeballing everything prior to making your cuts, you’re seeing something you don’t like, Craig recommends heading to the junkyard and finding a manifold that will fit and that gives you the layout you want. In this particular build, Craig used two passenger-side manifolds because doing so allowed him to ensure that the T4 flanges and wastegates on both sides were where he wanted them to be to maintain the balance and symmetry of the engine compartment. On the passenger side of the block, he simply flipped the manifold so the exhaust flange was located towards the front instead of the rear.

Install the Feed Pipe(s) and T4 Flange(s)

With the exhaust flanges cut off, hang the manifolds and loosely install a couple of bolts just to keep the manifolds in place. Getting the pipes to the T4 flanges just right is a matter of eyeballing, measuring, and cutting carefully. Craig leaves the pipes a little long on both sides so he can trim to fit. This takes a little longer but means you don’t end up wasting pipes.

The passenger side manifold with the turbo feed pipe tacked in prior to welding.

The passenger side manifold with the turbo feed pipe tacked in prior to welding.

To get the height right for the placement of the turbo T4 flanges, Craig spans the engine compartment with a straightedge and measures with a tape measure, but you can use a 2X4 or a broom handle. For this particular installation, Craig used portions of two 90 degree bent pipes to make the T4 flange adapter pipes.

Placing these pipe sections up next to the manifold, he moved them around until he got the look and location he wanted and marked them with a Sharpie where he wanted to cut. On the passenger side he also used the slip-fit section off another pipe section to extend the pipe just enough to balance out the turbo height.

Making the pipe fit the T4 flange takes a little work.

He then slowly squeezes the open end of the pipe into an oval to match it with the turbo flange. He recommends taking your time with this because you can easily squeeze too far. He then tacks one side in firmly and uses the vise and a drift punch to get the fit as close to perfect as possible before running beads around the circumference of the joint. Craig does this in steps as it allows him to heat the pipe up and stretch it into the corners of the flange to get a better fit. After that, he ran the beads to fully seal the joints.

With a little work, this is the end result. Two manifolds prepped to install twin turbos.

The twin turbos you see in the pictures here are made by Craig’s company Justin Sane Racing Products, but you can use any matched set of turbos you want. The installation process will be the same.

 

About the author

Mike Aguilar

Mike has been wrenching on cars since the early 1970s when he worked at his dad's auto repair shop. By the age of 14 Mike had built his first performance suspension, and by 16 he had built, and was racing cars in several sanctioned events in the San Francisco bay area.
Read My Articles

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