Mauro  Mar 31 2006 - 5:02pm   

This conversion was done on my 1990 Camaro RS 305 TBI, my goal was to make the conversion as clean and as easy as possible.

Before you start I will warn you this is a major change to your car and will take a lot of work and time.

I started out with a partial TPI. Runners, plenum, base, 22# injectors, the bolts for the runners and from the base to the heads. The TB is from an 89 Vette, I lost the PN for the bolts.

Here is a list of what you will need:

• HELMS Manual you will need this!!!!!
• Sensors & Electrical
• #25036979 x2 Coolant Sensor & MAT sensor (You can use one from your TBI)
• #16137039 MAP Sensor (You can use your TBI map sensor it's the same part #)
• #10456019 Knock sensor for 305 TPI (You must change this!)
• #25036979 IAC Valve (The TBI IAC look's the same, But I have not checked if it is the same PN as the TPI one)
• ECM #1227730 and a PROM for a Speed Density 90-92 TPI, V6 ECM's are the same (I got mine from a rolled 92 Firebird at the junkyard) but you will have to change the PROM to one for you engine size the V6 Prom will not work. (The ECM will have the PN on the front, so look before you buy)
• #12080890 1990 TPI Engine Harness (Only $241 from Dal Lambert)
  I chose the GM engine harness simply because it is the most complete. There are other choices, Painless Wiring makes a harness which costs $10 more form Summit, but does not come with half the wires and connections that you will need. If you were putting a TPI in a hot rod with no AC, wipers, Gauges etc it would be fine. The other choice is to send your TBI harness to Howell to be converted to a TPI harness, this is just as good but it will take them 2 weeks to do.
• Throttle Position Sensor (Got mine form a junkyard V6 MPFI)

(Optional, but recommended) Dual Fans. If you are changing to dual fans you will also need:

• An extra fan relay just like the one on the driver side firewall, which is identical to the fuel pump, relay next to it. The part number is printed on the top of the relay. (They are all the same)
• Dual fan supports, the part that is on top of the radiator which holds the fans in place, as well as the bottom dual fan support.

Misc.:

The fuel lines are essential you will be going from 12-14 psi fuel pressure to about 50 and the TBI fuel lines will not cut it!

• Metal fuel and return line from fuel rails to rubber fuel and return lines, which then go to the metal fuel lines in the chassis.
• Metal fuel line which goes from the in tank fuel pump to the fuel line in the chassis.

Here are the PN's:

• #10055874 & #10055875 Fuel pipes from fuel rail to rubber fuel lines.
  These are the rubber fuel lines from the fuel pipes to the chassis fuel lines, as well as the high-pressure pipe/hose from the fuel pump to the chassis fuel delivery line (I had to change this, the part may be the same one form a V6 car).
  #10038113 #10113094 #14089403 (I don't know which is which).

• TPI fuel pump. You can use a MPFI V6 pump but it is such a pain to change I recommend a new Walbro in tank.
• Fuel pump sending unit from a TPI car or a MPFI V6 (I got it from the junk yard)
• #10148097 Complete TPI Gasket Set
• #10163822 Throttle Cable (TPI) the TBI is too short
  If you have an Auto you will need to change the TV kickdown cable, and if you have cruise control you will have to change the cable as well.

You may not need all of the following:

• #10077566 Throttle Bracket on side of Plenum
• #17113544 Injector O-Ring set (top and bottom)
• #10096141 MAP Sensor mounting Bracket
• #10105251 Ducting from air cleaner to TB
• #11514149 x4 Bolt, attaches (1) MAP housing to Plenum (3) Throttle bracket to Plenum
• #14088537 Fitting for side of plenum (EGR)
• #14082470 x2 Fitting for side of plenum (FPR and MAP)
• TPI Air cleaner assembly (Junk yard, they are the same for the V6 Camaros)

You will also need lots of new hoses. This is a fairly complete list, but I may be forgetting something.

Procedure

First disconnect the battery and then proceed to remove the TBI air cleaner assembly.

Unplug all the TBI sensors and find the Engine harness. Caution don't get confused with the accessories harness, don't go nuts and just disconnect everything just what is part of the engine harness.

You will have to disconnect:

• The wires at the starter, knock sensor and fan switch (both on pass side of the engine)
• The bolt's on the back of each cylinder head that are grounds, you will need to remove the bolt to free the grounds from the harness on each side.
• Unscrew and remove the bulkhead connector (big black thing that goes from the harness to the drivers side firewall, you will need a screwdriver.
• TBI Electronic Spark Control, fuel pump relay and fan relay. These are all located on the driver's side firewall. The ESC you can remove you will not use this for the TPI.
• The connectors from the charcoal canister, brake proportion valve located under the master cylinder and the connector from the power steering pump (You will not need to connect anything here, at least my TPI harness did not come with a connector.
• The oxygen sensor, temp sensor (on the side of the driver cyl head) as well as the connector from the oil pressure-sending unit and under the car the VSS sensor and the park neutral switch.
• The TBI fuel injectors have to be unplugged from the harness as well as the TPS and IAC valve as well as the distributor.
• The two connectors for the smog pump.
• Remove the spark plug wires

Under the dash on the passenger side remove the upper and right kick panel. Lower the ECM and disconnect the harness. Remove the clip that holds the harness to the fender and pull the harness form the engine bay up, store the clip you will need it to secure the new harness to the fender. Don't throw the harness away keep it handy you will might need it as a reference.

Remove the distributor, mark it so you can put it back in the exact same position.

Now you can start removing the TBI. Relieve the pressure from the fuel lines and remove them, fuel might start to leak from the open fuel line so attach the new TPI fuel lines and move to a high place on the strut tower to stop leaking, you might need a jar.

You don't have to take the TBI off the intake manifold. Remove the bolts that hold the intake manifold to the cylinder heads (if you plan of reusing the TBI manifold remove the bolts in the reverse order of the torque sequence in your helm manual to ensure that you don't warp it. You will have to pry the manifold off with a big screwdriver or a crow bar.

Clean the gasket residue from where the cylinder heads meet the intake manifold and where the intake manifold meets the block in the front and back.

You might have to remove the alternator to remove the driver side valve cover as well as the accessory brackets to remove the intake manifold and install the fuel lines. When I did this I changed the camshaft and the heads so I don't remember if you need to remove these or not.

NOTE: You don't have to do everything in this order.

Ok once you have removed the TBI and TBI harness, you can proceed to install the TPI. I started with the TPI base. I used some contact cement to glue the new gaskets to the cyl heads and a 1/2 inch coat of RED RTV sealant on the front and back ledges of the engine to seal the manifold. Torque it down to the Helm manual specs. Next I presented the new harness into the engine bay, by just laying the different branches in the general area of where they are supposed to go. Connect the harness grounds on the rear of each cyl head. Bolt the runners to the intake manifold and then go on with the injectors and fuel rails, the Helm manual recommends you put a little engine oil on the o-rings before you install the injectors. Put the distributor back into place (Be Careful!! try to put it back into the same position it was when you removed it), and you can proceed with the plenum and TB. At this point you can connect all the jumpers from the new harness to the sensors.

What goes where?

Intake Manifold
At the very front you have a metal fitting which is where coolant comes out of the manifold. From there is should go to the TB but I routed it straight to the heater switch

On the Drivers side half way down the manifold, between the two sets of runners there is a fitting which you need to buy a rubber hose and connect to the PCV valve on the drivers side valve cover.

Plenum
On the Pass side at the back there are 3 fittings, 2 which are on a recessed area and one on the very side. The two on the recessed area are as follows 1) Fuel pressure regulator 2) MAP sensor. I plugged up the third one.

NOTE: (This is not the way it is supposed to be set up, one of the two recessed connectors should have a T in the rubber and go to the EGR solenoid. Which I did not hook up. Same with the EGR valve which is in place but not hooked up as well as the plugged fitting. I will post a follow up article when I get around to it.)

On the passenger side rear bottom corner there is a fitting which you need to connect with a hose to the brake master cylinder.

There is a hole under the plenum, which is for the MAT sensor. I got a V6 air cleaner, which mounts the MAT sensor on the air cleaner itself.

Throttle Body
On the pass side of the TB there are two spots for hoses to be connected. The top one (larger one) goes to the crank case breather on the rear of the pass side valve cover. The bottom (smaller) goes to the charcoal canister. Under the TB is the IAC housing which has the IAC valve and the coolant passage. I performed the TB bypass and did not hook this up.

I had a problem with the GM TPI harness. It had this mysterious connector with two thick wires one orange and one red. Which was laying way out of place right behind the pass side strut tower. To make a long story short this turned out to be the wires which give power to the ECM and the fans. Not a big problem a little cut and splicing and connect them to the battery with a fusible link. The harness also did not come with the wire that goes from the back of the alternator to the battery. Small detail because the alternator will not charge without this wire. I ripped the one out of my TBI harness and used it.

First time I started the car the timing was way retarded, and it backfired out of the TB and cracked the top of the air cleaner assembly. Before the car is ready you will have to adjust the timing, the TPS as well as setting minimum idle.

Other than the problems listed I have had no check engine lights and the car runs fine!

Any questions or comments please e-mail me.

Mauro Giambruno (mg42759@csun1.csun.edu)
www.sc3gfb.org (SoCal 3rd Gens)