Installation Procedure: Fuel Injection Throttle Bodies for Corvair Engines (except Turbo)

1. Install a 5/16" fuel return line. The original fuel return line (if so equipped) is too small for a recirculating system.  After trying to add a Tee to the vent line or brazing a return line to the gas gauge sender, I ended up brazing a tube to the gas filler neck.  The tube extends down inside the gas tank well to make connection easier.  The next one I try will have the fuel return line on the same side as the vent line.  The version shown cannot be installed when attached to the tank.  The gas tank must be removed before removing the filler neck and the sway bar must be removed before removing the gas tank.  Be sure to spray all of the fasteners with a rust penatrent before attempting to remove the fasteners.  It took longer to drill out a broken sway bar mounting bolt than the remainder of the task.




2. Mount the high-pressure fuel pump.  I first mounted the pump under the floor pan near the gas tank.  The high-pressure fuel pump under the floor was so loud that I finally mounted it in the engine compartment on a double isolation mount to reduce the noise transfer. I put a low-pressure fuel pump under the car to feed the high-pressure pump. The fuel filter is mounted below the pump.

In the future, I will mount the fuel pump in the tank to reduce the noise. Ray Sedman of American Pi offers an in-tank conversion kit. These will be available as complete conversions with new tanks or as a kit for customers who would like to weld the adapter plate in their tank..

3. Mount the air temperature sensor to sense the temperature of the inlet air.  I plan to drill a hole in the air filter housing using a step drill.

4. Mount the “coolant temperature” sensor in the lower shroud.  I used a simple angle bracket attached using the thermostat mounting stud.  This location may get a little too warm.  The previous location in the front heater duct did not get warm enough to turn off cold enrichment.


5. Mount the MegaSquirt controller and relay box in the interior.  I used the shelf above the transaxle.  From left to right in the photograph: SafeGuard ignition controller, Innovate Motorsports LC-1 wide band oxygen sensor controller, terminal block, MegaSquirt relay board and the MegaSquirt fuel injection controller. For the next installation, I will mount everything on a plate and connect as many wires as much as possible before installing the plate.


6. Cut close fitting holes in the firewall for the wiring harness and vacuum/pressure hose grommets. The wiring harness contains 4 or 8 wires for the fuel injectors (2 each), 3 wires for the throttle position sensor, 2 wires for the manifold air temperature sensor and 2 wires for the idle air control if used.  There are also 3 wires for power, switched power and ground, 2 wires to the fuel pump, 1 wire to the ignition coil and 2 wires to the “coolant” temperature sensor (another 8).  The wide band oxygen sensor cable has 7 wires.

7. Remove the air filter components and save them for reuse. Remove the throttle linkage crossbar and save it for reuse. Remove the Rochester H carburetors and the original mechanical fuel pump and fuel lines. Remove the choke links. Carefully remove the carburetor studs from the pads on the cylinder heads. The inner carburetor studs are frequently difficult to remove because fluids in the recess corrode the stud. Soak the threads with a penetrating oil such as PB Blaster or Kroil or a 50/50 mix of acetone and ATF. Use a stud remover and carefully turn the stud back and forth until it can be screwed all the way out. Then clean out the threads with a tap. This is very important since the socket head cap screw that attach the throttle bodies also locate them based on the positions of the threaded holes.

Install the fuel injectors and fuel rails on the throttle bodies. Install the throttle bodies using the supplied socket head cap screws and O-rings.  Install the throttle linkage cross shaft to the throttle bodies using the supplied socket head cap screws. Attach the down links to the throttle linkage cross shaft and the throttle body throttle arms using the supplied lock nuts. The longer link goes on the right side. Adjust the right side down link first if needed so that the arm of the cross shaft clears the bracket and throttle body. If adjustment is needed, loosen the lock nuts on the threaded shaft and disconnect the top rod end from the cross shaft arm screw or unscrew the rod end to shorten or lengthen the down link. Reattach the rod end and tighten the lock nuts.

Now adjust the left side down link so that both throttles are closed at the same time. Verify that the linkage moves freely through the full range and that both throttle plates are wide open at the same time.

Form connecting fuel lines for the fuel supply and return.  Attach the wiring harness connectors to the fuel injectors and sensors.


Now the air filter can be installed. Use the longer J-bolts supplied with the kit to attach the connecting tube to the throttle bodies.

8.  Install the wide band oxygen sensor.  Weld a sensor bung into the crossover pipe after the junction.

9.  Verify that there are no leaks in the fuel system under pressure.  Connect a computer running MegaTune software and verify that the sensors are giving correct readings.  Then start it up.  The engine should start within a few tries as soon as the fuel lines are primed with fuel.

10.  Tune the fuel table using the MegaTune and MegaLogViewer software.  A attach a laptop computer with the MegaTune software to the MegaSquirt controller using a serial cable and then drive the car while data logging.  The datalog file is then opened with the MegaLogViewer software and the fuel table is recalculated using VE Analyzer.  The new fuel table is then downloaded to the MegaSquirt controller and the test is re-run.  Individual cells in the fuel table can be fine tuned as required.  The data can be graphed for analysis.


MegaTune Screen

MegaTune VE Table Tuning

MegaLogViewer screen

MegaLogViewer output graph

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Last Update:  December 15, 2008 2:06 PM
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