Justin Sane Twin Turbos a GMC 2500 HD with 6.0 LS Part 3

engine swap twin turbo
Every Turbo installation project requires valve train upgrades to get the most out of the new turbo(s).

Check out Part 1 HERE

Check out Part 2 HERE

When turbocharging an engine, you’ve got to upgrade certain parts of the valvetrain. We’ll observe Craig as he removes the old cam and installs the new cam. The stock cam will work with a turbocharged engine, but in order to make maximum power, a new cam is definitely required. Since we’re there already, and this engine has over 300 thousand miles on it, we’ll also do a quick walkthrough of changing the oil pump, which on these engines is driven by the nose of the crankshaft. Then we’ll watch as he swaps out the weak stock valve springs that will cause valve float on a turbocharged engine and installs heavier springs without having to pull the heads.

One recommendation that I have before we start is that as you remove nuts and bolts, put them into small containers, separating them as to what they were securing: Bolts for the AC compressor in one container, radiator components, timing cover, etc. This way nothing gets mixed up. Anyway, let’s take a look at part three of the JS Racing Products Parts Truck build.

Pull the Drive Belts and Accessories to Access the Timing Set

engine swap twin turbo
The first step in the valve train upgrades is to access the timing set.


Getting to the “guts” of the engine to change out the cam and oil pump isn’t hard, it’s just time consuming, and, if the engine is still in the vehicle, uncomfortable. You’ve almost got to be a contortionist to get in there. However, you don’t have to pull everything to do it, just the stuff directly in front, such as the AC compressor and the water pump. Be careful as you move the compressor around; you don’t want to break any connections causing a loss of refrigerant.

Drain the radiator into a catch pan and dispose of the old coolant safely and appropriately-shops like Jiffy Lube and Autozone accept used coolant. Remove the drive belts and radiator and heater hoses. Craig clamps a C-clamp to the fan pulley and uses his air chisel to loosen the fan. If you don’t have one of these, you’ll need to use the appropriate sized wrench. Think heavily about discarding that power-robbing mechanical fan and installing an electric one, if your vehicle isn’t already equipped with one. Later in the series we’ll walk you through pinning out the ECM to supply power to electric fans.

engine swap twin turbo
Craig’s come up with a cool trick to remove the fan on LSx engines. He clamps the water pump pulley with a C-clamp and then uses his air hammer with a chisel bit to “blap” the fan loose. If you don’t have an air hammer, use a regular chisel and hammer. It’ll just take a little more effort.

Now that the radiator and cooling system are fully drained, it’s time to remove the radiator and fan shroud (upper and lower halves). Check inside the filler neck and/or hose openings for the presence of rust. If you see any, seriously consider pouring some cooling system cleaner into it and letting it soak for a bit or sending it out to be rodded and cleaned while we finish this part of the upgrades.

Loosen the air conditioning condenser and very carefully swing it out of the way like a door. As you slowly swing the driver side of the condenser out from the front of the vehicle, support and move the AC hoses so the aluminum lines don’t bend or kink. This will give you a bit easier access to the front of the engine and give you the room you need to remove the old cam and install the new one.

engine swap twin turbo
The crank pulley has to be removed to remove the timing cover. A good three-jaw puller is indispensable for this.

The water pump came off next (six ten mm bolts, three per side) and was set aside for reuse since it was in good shape still. Craig then used his air impact gun to remove the crank bolt. A good three-jaw puller was used, along with the impact gun, to remove the crank pulley. The removal of the timing cover’s ten mm bolts (four on either side and two at the front corners underneath) and a little wiggling of the cover gave him access to the timing set.

Installing the New Cam and Oil Pump

engine swap twin turbo
The timing cover comes off, giving us access to the timing set.

Because this engine has more than 300 thousand miles on it, Craig decided to replace the oil pickup and the oil pump. In these engines, the oil pump is mounted to the front of the crank and driven by the crankshaft. It’s removed by removing four bolts, two per side. The new oil pump is just a high volume GM replacement pump, nothing overly fancy. It needs to be high volume because the turbos require oil for lubrication and cooling of the bearings.

engine swap twin turbo
The EOM oil pump is removed by removing the four ten mm bolts at the corners.
With the oil pump off, rotate the engine to line the cam and crank timing marks up before pulling the cam gear.

With the old pump sitting in the scrap pile, the crank bolt was reinstalled so the crank can be rotated to line up the crank and cam timing marks (See image). There are three ten mm bolts securing the cam gear to the nose of the cam. With these removed, wiggle the cam gear off the front of the cam and let the timing chain drop. Next, remove the four cam keeper/retainer bolts (ten mm or large Torx head) and the cam retainer plate.

engine swap twin turbo
To get the cam out, these four bolts and the cam retainer plate need to come out.

Next, loosen the rockers (eight mm bolts) until there is no spring tension on them. Craig then threads two water pump bolts into the face of the cam and spins it by hand several times. This pushes the lifters up and sets them so they’re off the cam lobes. He then inserts the two oak dowels in the holes directly above the two retainer bolts on either side, slowly and carefully until they bottom out completely. This ensures that the lifters don’t drop into the oil pan when you pull the cam out.

engine swap twin turbo
Craig’s ultra-high tech lifter retainers are actually half-inch oak dowels that he shaped one end of each to a point.

The water pump bolts are now used as handles to help you carefully and slowly remove the cam. Again, slowly and carefully remove the cam. You don’t want to nick up the cam bearings while doing this. Keep the cam steady and level with the cam bore.

engine swap twin turbo
Use water pump bolts to help you remove the cam. I can’t stress how important it is to take this step slowly and carefully. A nicked or, even worse banged-out, cam bearing means you’ll need to pull the engine out and apart.

The new cam Craig installed was one of his own Spec 2 cams. This is a fairly mild cam as compared to those that many install with lift of around .600 and a duration of around 200 or so (he keeps the exact numbers to himself.). The two water pump bolts are transferred over to the new cam and it is then very carefully and slowly slid into the cam bore. Again, be very careful doing this. You don’t want to nick or pop a cam bearing out. Once the cam is fully seated, the dowel rods are removed and the removal process is reversed to finish the new cam installation. Be sure to lube the new cam before installing it. Craig likes to use regular engine oil, while I prefer engine assembly lube. Take your pick.

engine swap twin turbo
The old cam is out and we’re ready to carefully slide the oiled-up new cam in.

Once the cam gear is reinstalled, making sure the timing mark is at the bottom and directly opposite the timing mark on the crank gear, add a couple drops of Loc-Tite to the cam gear bolts and torque them down Craig says just be sure they’re “good and tight,” but I prefer to torque them to spec. With the timing chain reinstalled, it’s time to slide the new oil pump over the front of the crank and reinstall the four bolts that secure it. I would recommend a couple drops of Loc-Tite here and to make sure the bolts are tight.

engine swap twin turbo
Transfer the water pump bolts to the cam to use as supports again.

The timing cover has a little trick to it. Place the cover up against the block and run the eight perimeter bolts down most of the way, but don’t tighten them. Next, install the crank pulley and then tighten the timing cover perimeter bolts and the two from the oil pan. This ensures that the cover is centered to the crank pulley and the seal doesn’t leak. Reassemble everything else, and you’re done replacing the camshaft and oil pump. Craig’s got some other tips and tricks for cam swaps in a video he posted covering the process.

Turbocharging Requires Stronger Valve Springs

engine swap twin turbo
The stock valve springs (left) need to be replaced by newer, stronger springs to keep up with the turbos.

One of the main robbers of power and efficiency in high performance engines is valve float. This is enhanced when you add boost to your engine. Valve float is the phenomenon where the valve springs are unable to fully close the valve when the engine is turning at high RPMS. It can actually kill an engine. This is why whenever Craig turbos an engine he pulls the stock springs and installs stronger ones. Additionally, this engine has over 310 thousand miles on it.

engine swap twin turbo
This handy (and cheap) little valve spring compressor is easy to use. Just remove the rocker arm, slide the tool over the rocker stud, and tighten the rocker bolt. This image shows the spring compressed sufficiently to expose the valve keepers.

There are two ways to change valve springs without letting the valves drop into the cylinder. The most difficult is to pull the heads and swap the springs out. However, that method takes too long. We can change the springs without pulling the heads by adapting our air compressor to our compression tester and dialing the pressure down to about 40 pounds per square inch (PSI). The external air pressure pushes on the valve and keeps it from falling into the cylinder as we swap the springs. These are the steps he followed to swap the springs after the valve covers were removed:

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The exposed keepers are removed with a magnet.

1. Out came the spark plugs
2. He threaded the compression tester into the plug opening, and
3. Attached air line from the compressor
4. He used a bar-type valve spring compressor attached to the rocker stud
5. Tightening the rocker stud nut compresses the spring, giving access to the valve retainer
6. A magnet was used to remove the spring retainers
7. He loosened the rocker stud nut and removed the compressor and spring
8. The new spring was slid over the valve pedestal
9. The rocker stud nut was again tightened to compress the valve spring, and
10. The valve retainer was reinstalled, allowing him to
11. Loosen the rocker stud and remove the bar-type valve spring compressor.
12. Move the compressor to the exhaust valve and repeat.

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This is what bank 1 looks like after all the valve springs have been upgraded.

There are a number of different types of spring compressors that allow you to change valve springs without pulling the head. I recommend the type that allows you to compress both intake and exhaust valve springs at the same time.

Craig’s purpose behind this build was to show us how we can fairly quickly and easily pump up our LS engines for the lowest cost, so he didn’t swap out the valve seals, but since the engine was “farting” a little bit of blue smoke at startup, I recommend changing the seals.

About Mike Aguilar 388 Articles
Mike's love of cars began in the early 1970's when his father started taking him to his Chevron service station. He's done pretty much everything in the automotive aftermarket from gas station island attendant, parts counter, mechanic, and new and used sales. Mike also has experience in the amateur ranks of many of racing's sanctioning bodies.

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  1. Justin Sane Twin Turbos a GMC 2500 HD with 6.0 LS Part 4 - The Burnout

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