LS1 Bolt-On Modifications - Turning Wrenches - Part 1

In order to relieve fuel pressure from the intake manifold's fuel rail, the valve stem cap is removed from the front of the driver-side fuel rail, and a Schrader valve tool is used to remove the valve. The pressure was relieved slowly, and a rag was put under the Schrader valve to catch any fuel from spilling onto the manifold. Once complete, on the driver-side fuel rail, a fuel-line-disconnect tool is used to separate the fuel line from the manifold.

The coil pack harness is removed by pulling the blue retaining clip toward the front of the vehicle and then unsnapping the electrical connector. After moving the wiring out of the way, toward the inside of the manifold, the process was repeated on the passenger side. Then the fuel system EVAP hose, which is retained with a clip, and runs from the drivers-side fuel injection rail to the intake manifold is removed. A flat-bladed screwdriver is used under the clip to pop the outside section off. Pushing forward on the clip pushes the rubber connector back to pull the hose free.

In order to remove the injector connections from the injectors, a flat-bladed screwdriver is used to push up on the metal clip on the bottom until it releases. All eight fuel-injector connectors are moved to the outside of both sides of the intake manifold.

Next, the cables are removed from the throttle bracket by pushing up on them with a small flat-bladed screwdriver. The EGR tube is gently lifted out and rotated forward and toward the passenger side, away from the intake manifold.

The PCV valve is removed by pulling on the valve to separate it from the line attaching it to the throttle body. Once complete, the intake manifold ground strap is removed with a 10mm socket.

All 10 8mm intake manifold bolts are loosened, but only the front six bolts are removed. The back four bolts will not come out of the manifold due to interference with the cowl, so rubber bands are used to hold up the bolts in order to keep them from falling down and preventing removal of the manifold.

To make sure nothing will obstruct removal of the intake manifold, all wires and connections are moved to the outside of the manifold. The power brake booster hose is pulled off at the brake booster, and then the intake manifold is carefully pulled upward and forward approximately 6 inches. Reaching behind the manifold, the electrical connection for the manifold absolute pressure (MAP) sensor is disconnected, as is the vacuum line beside the sensor. The brake booster hose is then guided out as the intake manifold is pulled forward and removed.

Once the intake manifold is removed, the loom that covers the engine knock sensors is cut open. The two clips that hold the knock sensor wires and the coolant bypass hose that runs from the rear to the front of the manifold together are removed. Front and rear coolant bypass lines are taken out using a socket on the four 10mm retaining bolts. In the four boltholes there are four seals that mate the boltholes and the bypass tubes. Any seals that were not attached to the manifold are removed, as are the rubber bands from the manifold.

Since the LS1 intake manifold attaching parts will be reused, after getting the manifold to a bench, the parts disassembly continues. The back of the manifold contains a connection for the brake booster hose and manifold vacuum, as well as the manifold absolute pressure (MAP) sensor. A pair of pliers are used to spread the brake booster hose clamp and then to pull the brake booster hose off the vacuum port at the back of the manifold. A flat-bladed screwdriver is used to expand the MAP sensor clip, thus allowing the MAP sensor to be removed. Please note that this used SLP LS6 intake manifold didn't come with a MAP sensor, but a new SLP/GM LS6 manifold will have a new MAP sensor.

The fuel rails that hold the fuel injectors in the intake manifold are retained with two 10mm bolts on each fuel rail. Four bolts are removed, and then firm, even, upward pressure on the fuel injectors is applied until they pop out.

EVAP canister lines and canister are removed from the manifold by pushing down on the gray retainer clip with a flat-bladed screwdriver.

Two 10mm bolts retain the throttle cable bracket. After removing the bracket, the rubber hose that connects the PCV valve to the manifold is pulled out, as are the four retaining clips that slip into the top of the manifold over intake runners 1 and 7 on the passenger side and 2 and 8 on the driver side. If a used LS6 manifold is on your wish list, make sure it is F-body spec-ific, as the Corvette LS6 intake doesn't have provisions for a throttle bracket.

The throttle-body gasket is slipped out of the LS1 intake and a new gasket is installed. A GM-sourced LS6 manifold will not have a hole drilled in the top of it for EGR provisions, but this used SLP LS6 manifold does. SLP cuts a hole in the manifold and uses a 3/4-inch pipe and nut that will connect to the factory EGR tube. Since this manifold was used, the owner wisely purchased replacement SLP EGR O-ring seals. One O-ring is slipped over the pipe and bottomed out, and the fitting is pushed up to mate with the underside of the manifold. The second O-ring is then slipped over the pipe threads that come out of the top of the manifold, and the fitting is retained with a nut. A 1-3/16-inch socket is used on both ends of the fitting to secure it. [If you don't want to retain EGR functionality, purchase the GM and/or SLP LS6 manifold (without EGR provisions) and an EGR block-off plate for the passenger-side exhaust manifold. In addition, if the EGR valve is made nonfunctional, the Bird's powertrain control module (PCM) will set an SES code; that is, unless you have your favorite tuner reprogram your PCM to delete the EGR error.]

After flipping over the LS6 intake manifold, a new set of GM intake manifold gaskets are inserted dry into the cast-in intake gasket flanges. Only when you flip over the LS6 manifold will you notice any appearance difference from the LS1 manifold (other than EGR). In this case, the bottom of the manifold is almost flat (versus a curved underside on the LS1), and this allowed the runners to gain additional volume. The manifold is then turned back over to prepare the fuel-injector rails for installation. After applying silicone grease to the manifold side of the injectors, the fuel rail and injectors are lined up in position and then carefully popped back into the manifold. The four 10mm fuel rail retainer bolts and the fuel rail Schrader valve are installed, and the rest of the parts are swapped from the old to the new intake.