This page will detail the removal of the old TBI system and installation of the TPI system, including modifications to the original TBI system components to be reused. Detailed instructions regarding the new wiring harness and computer are cover in the "Computer & Wiring Harness" section.
1. Note Donor System Attributes: 3. Recondition the Intake, Plenum & Fuel Rail System: 4. Prepare the Suburban Engine Compartment for the TPI Swap 5. Install the TPI Intake Manifold and Fuel Rails 6. Install the Computer, Harness, Distributor, Runners & Plenum
1. Note Donor System Attributes:
As I have stated before, I will be installing the TPI system from my 1991 Firebird GTA (5.7L) to my 1994 Suburban (5.7L). Since both are stock applications, the chip provided by S&P for my truck is for stock/mild performance applications. Another important item to note is the differences in the intake manifolds. Because both of my engines use the 87' and later iron cylinder heads, the center pair of intake bolts are canted and will interchange without issue. If you are swapping a pre-87' intake for iron heads or Corvette aluminum heads, the center bolts use the traditional bolt angle. If this is the case, the intake will need to be modified to permit the newer angle. S&P can do this for you, if you cannot find a local source to perform this modification.
Stock TPI units incorporated a feature that helps keep the throttle body from icing up in extremely cold climates. Hot engine coolant is circulated through the bottom of the throttle body (reference two nipples on the third picture). Coolant exits the front of the intake under the throttle body (TB), then a short curved piece of hose connects to the TB, then from the TB is goes to the heater core connection (reference the fourth picture). Since I live the southeast, this will not be an issue, so I will simply bypass the TB. To do this, I will go directly from the intake nipple to the heater core connection. For a stock TBI intake, the heater core is fed from the rear passenger side via performed hose. The stock hose will not be reused. If you look closely in the fifth picture, you can see the rear heater hose just over the rear part of the passenger side valve cover.
Since I will be using the EGR and charcoal canister on my Suburban, I made note of these items and how they were installed on the GTA. The EGR solenoid is covered in the previous section, but will also be discussed here as a reference. The EGR is installed in the center of the intake manifold, under the plenum. If this has not been replaced recently, for obvious reasons, I would recommend changing this out before installing the plenum. The EGR solenoid is installed on a bracket to the passenger side of the distributor, under the coil. I will use the GTA solenoid and bracket on the truck. The vaccum source for the solenoid comes from a small port under the throttle body (reference the second picture). You can see the small vacuum hose near the water neck in the third picture.
The solenoid for the charcoal canister is located directly above the canister in the GTA (reference the fourth picture). However, on the TBI setup, it is located between the water neck and throttle body, slightly on the drivers side (reference the fifth picture)
3. Recondition the Intake, Plenum & Fuel Rail System:
Note: If you are unfamiliar with the TPI system, I strongly urge you to purchase S&P's two part video series and watch it before attempting this conversion. Mark Campbell takes you step-by-step through the entire process of reconditioning the TPI system, and at the same time describes the differences in TPI systems as they changed over the years.
Since I had recently changed the EGR in my GTA, the condition of my plenum, runners and fuel rail were in very good condition since I had cleaned them at that time. However, I did decide to install an O-ring kit for the tubes. In the past, I had installed an adjustable fuel pressure regulator. So I did not need to install a new diaphragm. When performing this rebuild, keep in mind that the fuel rails can only go together one way, so getting it wrong will not happen. Remember to wipe a little vasoline on the new O-rings and rock/twist them slightly when pushing the tubes into the openings. You don't want to pinch a new ring. They will go in easily. It is also very important to put a little anti-seize lubricant on the tips of the small torx screws. This will aide in installation and help prevent the screws for seizing when disassembling in the future.
Although it is not necessary, I had installed an adjustable fuel pressure regulator on the GTA. Therefore, it will remain when installed on the truck. Below is a picture of the stock regulator cover and two different adjustable covers. Both adjustable covers work the same in that they use a solid disk and a set screw/nut. Note the small security style torx screws used to hold the regulator cover in place. If you order an adjustable cover, it will generally come with this specialized bit, as well as upper tube gaskets. Note the fuel pressure regulator vacuum hose still attached to the plenum.
The GTA has nearly 200,000 original miles. Therefore, I was not too surprised at the condition of the intake manifold. The underside was covered in a heavy oil build-up. Nothing a little mineral spirits and some elbow grease will not fix. For the tough spots, I used some carburator cleaner and some steel wool. First I removed the splash tray, which is bolted to the manifold bottom with four 10 mm bolts. After thoroughly cleaning the manifold base, I tapped the threaded openings and blew them out with compressed air. The last step was to clean the intake manifold bolts in preparation to install later. I will be reusing the original GTA bolts, which are a #45 torx bit. If you do not have any bolts to reuse, I would recommend getting some stainless steel ARP bolts.
4. Prepare the Suburban Engine Compartment for the TPI Swap:
First and foremost, DISCONNECT THE BATTERY, negative side first. Drain the radiator fluid and remove the upper radiator hose. Remove all original harness connections. Typically, there are two TBI injector connections, but in my case, I had spliced in the Edelbrock MPFI harness. I clipped the MPFI harness connections and disconnected all other pieces, including: the MAP sensor, IAM, TPS, EGR solenoid, charcoal canister solenoid, temp sensors (intake & driver's side cylinder head), AC compressor (two connections), alternator, and grounds. Disconnect the throttle cable, cruise control, coil and distributor connections. Set all these pieces aside. Go ahead and disconnect the rear heater hose and the brake booster vacuum line and remove both completely from the truck. Note: there is a small 10 mm bolt tucked under the harness on the rear driver's side head (see picture below). Disconnect the supply & return fuel lines and be careful for there may still be fuel pressure. Remove the fuel lines completely from the truck, and remove the throttle body. Remove the AC compressor and the bracket (see next section). This will make access to the intake easier, and it needs to be switched out anyway. Since you have already removed the air box that attaches to the passenger inner fender, temporarily secure the AC compressor to the bracket. Bring the distributor to number one cylinder firing, and set the damper to zero degrees (0*) BTDC, which should be where the timing is set to factory specifications. Note the position of the distributor housing and rotor. You will want to reinstall the distributor in a similar position when restarting the engine. Remove the distributor and the TBI intake.
5. Install the TPI Intake Manifold and Fuel Rails:
Prior to cleaning the cylinder head surfaces and end rails, lay rags in the lifter valley and stuff paper towels into the ports, to prevent pieces of the old gasket from falling into ports and combustion chambers. I like to use new razor blades to scrape the surfaces clean of thicker deposits of old RTV, gasket, carbon, etc. Having a shop vac handy helps with removing particles as well. When clean, remove paper, making sure that all particles fall on to the rags in the lifter valley. Remove rags, and wipe gasket surfaces clean with rags soaked in lacquer thinner in order to remove all traces of oil or grease.
Replace all gaskets as recommended. I ordered a complete gasket set from S&P for my year TPI that includes the manifold gaskets, upper and lower tube gaskets, as well as a throttle body gasket. Check to make sure that you install the manifold gaskets right side up, if applicable. For the stock type gaskets from S&P, the embossed side goes up. Coat head surfaces and both sides of gaskets with Edelbrock Gasgacinch #9300 or similar adhesive such as Permatex "High Tack Spray-A-Gasket Sealant". Apply a silicone sealant around the water passages on the head surfaces. Gaskets and surface will become tacky to the touch within a few minutes. Carefully place gaskets on head surfaces, aligning the ports and bolt holes. Use a 1/4" thick bead of sealant across each end seal surface, overlapping the intake gasket at the four corners. Be sure to use an Oxygen Sensor safe sealant. I like using Permatex Ultra Grey RTV Silicone. Spray the top surfaces of the gaskets with some "High Tack Spray-A-Gasket Sealant" and some RTV gasket sealer around the water passages. Allow silicone sealant to become tacky to the touch (which only takes a few minutes). NOTE: Be sure to check the clearance you will have with the stock oil pressure sending unit before applying gaskets and sealants. I went to install the intake and quickly realized that I had a conflict. Luckily I had enough brass fittings on hand to rework the 90* elbow for clearance. Apply a thread sealer to the intake bolts. I prefer to use ARP's thread teflon thread sealant, with a small amount of of RTV sealant smeared under the bolt heads. Carefully position the manifold on the engine, centering bolt holes. Torque all manifold bolts in the sequence illustrated below. Tighten in three steps: snug, 20 ft/lbs. & finally 25 ft/lbs. If you are installing the coil per a stock TPI setup, don't forget to install the bracket on the passenger side rear (see photo below). Tip: Be sure to cover the distributor opening in the manifold until you are ready to drop the distributor. I like to use the stablilizer disk that comes with an oil pump primer, but a rag will suffice.
Go ahead and modify the nipple installed at the front of the intake BEFORE you install the fuel rails. As you can see in the pictures below, I used a 90* brass fitting and then routed the hose to the heater core fitting that was originally connected to the rear hose removed earlier. I used some RTV silicone on the threads. NOTE: Make sure the angle of the brass fitting is basically level (second picture from the right). I originally had it installed slightly up and it interfered with the IAC connection. I had to remove the plenum and rails to reset the angle. Note the bolt installed under the fuel rail connections.
Since my original injectors (left in picture below) had nearly 200,000 miles on them, I sent them off to S&P for a good cleaning and balance job. The $120 also includes new screens and O-rings. Install the fuel injectors into the rails, remembering to use a little vasoline on the O-rings. Gently twist/rock them into each opening and push the retainer clips into place. Install the assembly onto the manifold and secure in place with the four 10 mm bolts. Clean the coolant temperature sensor threads and install a new sensor. Some sensors come with a sealant already installed. If not, use anti-seize lubricant to ensure electrical ground.
6. Install the Computer, Harness, Distributor, Runners & Plenum:
Install the AC compressor bracket (see next section) and the AC compressor so that it will free up space to install the computer. Don't forget to reinstall the lower radiator hose. I installed the computer, fuel pump relay, ALDL connection and fuse block in the area that originally occupied the air box by using some simple brackets. Tuck the unused wire connections under the computer. Pull the unused VSS plug and transmission plug back and snap tie out of the way between the computer and overflow tank. Install the harness around the rear and under the fuel rail, including the following connections: fuel injectors, air temp sensor, IAM, engine coolant temp, and TPS. You can route all injector connections under the rails, except the rear passenger side. Go ahead and plug in the oil pressure sending unit BEFORE installing the distributor and bolt the ground to the rear of the passenger cylinder head, for the access is better at this point. Install the distributor and be sure to mark the no. 1 position on the cap. Plug in the new distributor harness connection and original coil to distributor connection. Install the EGR solenoid and be sure to plug in the connection BEFORE installing the solenoid. Position the coil in place and install the bolts. Note: I reversed the coil direction as installed on the GTA for better clearance with the old TBI harness. Go ahead and install the PCV valve and hose connection. If you need a new grommet, you can get an angled type in the HELP section of most parts stores (see photo).
Before installing the runners, note that there are four different size bolts. The longest bolts install in the bottom center holes (four each). The second longest bolts install from the backside (two each). The third longest bolts install in two locations (pass side - front bottom hole, driver side - rear bottom hole). The balance of tube holes (bottom and top) get the shortest bolts. Use anti-seize on all bolts and only finger tight until after the plenum is installed. Install the passenger and driver's side tubes. The gaskets have small plastic locater tabs that also hold them in place.
Clean the MAT sensor threads and install a new MAT sensor. Some sensors come with a sealant already installed. If not, use anti-seize lubricant to ensure electrical ground. Before installing the plenum, make sure both EGR vacuum hoses are connected, as well as the fuel pressure regulator vacuum hose. Install the upper tube gaskets, connect the MAT sensor plug and lower the plenum into place and install the bolts. Once all the bolts are in place and the plenum properly located, tighten all the bolts in a cross pattern. No need to overtighten these bolts, just get them good and snug. You can reach all bolts with one of the extensions in the picture below.
Plug in the TPS, IAM and engine coolant temp sensor plugs. Plug the 4L60E jumper connection "A" into the old MAP sensor, and tuck it behind the rear side passenger tubes. Splice the other two 4L60E jumper wires and oil pressure gauge wire. Connect the 12V battery wire to the starter and tap/splice the 12V ignition (run & start) wire. Note: Since my 94' Suburban has a power distribution block on the passenger side firewall, this is where I connected my 12V battery wire. Connect original harness grounds to the hole just behind the T-stat housing (Note: the front pair needs to be extended). I also had to cut the head off a small 3/8" header bolt for T-stat housing clearance (see picture further down the page). Install the AC compressor connections and driver's side coolant temperature sensor (for stock gauge). Install a new hose and connect the brake booster to the rear driver's side port. Since my 94' Suburban uses electric controls for heat and AC, I capped the unused vacuum port near the MAP sensor. Install the charcoal canister solenoid, plug and hoses. I fabricated an extension that attached to a small threaded hole (12 - 24X Machine Screw) on the passenger side. The port closet to the plug goes to the lower throttle body nipple. The other port runs over to the charcoal canister. After the charcoal canister solenoid is connected, install a length of 1/2" hose between the passenger side valve cover and upper throttle body nipple. Wrap all unused original harness plugs with some electrical tape.
Note in the above pictures that the original power connection to the coil will not reach the new coil location. This would require splicing and lengthening the wires. However, since I will be using an MSD 5 unit with a dual coil connection harness, splicing it will not be necessary.
Install the new knock sensor and connect the harness plug. Note: Have drain pan ready, for a good bit of coolant will come out of the block when you remove the old TBI knock sensor. Install the Oxygen Sensor plug. The new harness comes equipped for a one wire O2 sensor. However, my 94' Suburban came stock with a three wire sensor. The stock O2 location is under the front passenger floor board. Since I installed an Edelbrock TES with the new crate engine, this relocated the O2 sensor to the driver's side header/collector (see picture below). I had to extend the three wire connection to the relocated O2 sensor. For this TPI swap, I will leave the original O2 sensor 12v and ground connected, but splice the sensor wire to the new harness connection. If you do not have a three wire extension like mine, you could always buy one from S&P and accomplish the same goal, and leave the O2 sensor in the stock location under the passenger side floor board. Finally, splice the 12V start & run connection and the hot feed to the fuel pump. For my truck, the fuel pump wire runs down the driver's side frame rail. I simply cut and spliced the brown wire to the truck's gray wire, near the brake booster. Prior to connecting the new fuel lines to the fuel rail, be sure to purge the lines by running the pump for a few seconds. This exercise is required anyway when locating and verifying the original fuel pump feed. Go ahead and check the fuel pressure with the engine off (zero vacuum). Since my 91' GTA calls for 41-47 psi stock, I have my system set to 42 psi considering the mild nature of the stock replacement truck engine. To access the fuel pressure valve, temporarily remove the MAP bracket. Also, remove the original TBI fuel pump fuse and disconnect the original fuel pump relay.
Remove the original alternator and power steering pump, along with the original bracket (see next section). Reinstall both items using the new bracket, and plug in the original harness connection and battery feed.
Install new spark plugs (if desired), reinstall the spark plug wires, and install the rear plenum cover that covers the distributor cap.
Install a new 195* thermostat. With a TPI system, it is important to maintain proper operating temperatures and the factory rating of 195* must be installed. Note: The T-stat in the above pictures was the original and only installed to cover the opening. I installed a high-flow Mr. Gasket T-stat using the a standard late model water neck (below). Before installing, check the new T-stat for proper operation by boiling it in a pot of water. For the upper radiator hose, I cut about 4" off the original T-stat end. If you install it on the chrome water neck and give it a slight twist, you can actually reuse the original upper radiator hose. This will suffice until I can find something that fits a little better. In case you are wondering why I did not try to bring the water neck out the front, there just isn't enough room between the serpentine belt and clutch fan to safely route the upper radiator hose here. Coming from behind was the most efficient method to connect the two ports.
And don't forget to install a new air filter. I purchased and installed a cone style K&N from S&P. I am not thrilled about having my air filter so close to the hot air coming off the radiator, but until I can devise a way to route cold air in from the side, this will have to suffice. I am not even sure that a cold-air kit exists for this application since these trucks did not ever come stock with a TPI.
Go to the Accessories section to see how I finished the pulleys, new serpentine belt, fuel lines & fittings, and the new throttle cable.
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