ITB Assembly
Overview        Shafts & Couplings   Gaskets TPS
 
Overview
Extrudabody ITBs come assembled as individual throttle bodies with plates, shafts, and bearings in place, but they are not mounted to Base Plates or Air Horns.  You will need some basic mechanical skills and tools to put them together for your engine, most notably:
  • Metal hacksaw and vice to cut throttle shafts to length.  All of our shafts are made for 120mm bore spacing.  If you are using a Weber IDA-style Base Plate, you're in luck, no cutting is required.  If you are using any other bore spacing, you'll need to spend 5 minutes cutting each shaft to length. 
  • T-square or a good metal ruler to check your manifold for trueness.  If you are using a used carb manifold, you just need to make sure it's flat.  If it isn't, you'll need to true it up yourself with a belt sander, or sandpaper and flat surface, or take it to a machine shop to have it planed.  If you buy a manifold from us, no need to do this.

The information below covers basic ITB assembly.  Honestly, a lot of experienced mechanics and tinkers won't need to read any of this, but for most, reading this page before assembly will save you some time and effort.  You will also want to read the section Throttle Control next.

Steps to assemble our ITB packages:

  1. Make sure your manifold is true using a metal straight edge.  With the rule laid flat against the manifold in various positions, if you can easily see space between the ruler and manifold (usually one end or the other, or the middle), it's probably not true.  If it's not, see How to True an Intake Manifold.
  2. Test fit your Base Plates to the intake manifold and cut shafts to fit.  See Aligning ITBs for details.
  3. Slide the shaft Couplings onto the shafts as needed.
  4. Assemble ITBs to Base Plates, using a gasket in between (see the Gasket section below for more info).  Lightly tighten mounting bolts.  Note that the ITB with the Throttle Cam is usually mounted on the left of the system (when looking down at the ITBs with injectors on top pointing to the head).
  5. Position Couplings in place, set all Throttle Plates to fully closed positions and tighten couplings.

  6. Install TPS and check to ensure the plates can fully open without hitting the TPSes built-in stop. 

  7. Test opening and closing action of Throttle Plates.  Everything should open and close pretty easily at this point. 
  8. Tighten all Base Plate mounting bolts to about 10lb-ft.  We recommend you use Blue Loctite to secure bolts in place.
  9. Mount ITBs to your intake manifold.  Here you need your own gaskets or gasket making material.  At this point, you need to make sure you have clearance to tighten up your manifold nuts or bolts.  If you don't, usually a smaller head bolt will be a good workaround (such as a sockethead), or some light grinding of the manifold.
  10. With the ITBs mounted securely, again test the opening and closing action of Throttle Plates.  There will usually be enough resistance in the system that some torque is required to move the Plates, but it If it was working fine before you mounted it to the intake manifold and now it seems tight, it could be that your manifold is not true after all.  Or, you might have to loosen and retighten a Shaft Coupling or two. You may need to mount the Couplings in a different orientation so that they flex more (see section below). 
  11. With the above parts together and functioning well, install in any order
    • Idle Air fittings with gaskets or Air Plugs (above and below injector location)
    • Air Horns and/or Extensions with Gaskets
    • Throttle Cable Holder with Stand-off
  12. Install your fuel injectors into the ITBs.  Lubricate the o-rings first with some light oil (motor oil is fine).  It will take a bit of pressure to get the so that the o-ring is fully within the ITB.
  13. Install the fuel rail as diagramed in the Fuel Mounting page.

  14. Install the Throttle Cable holder.  See Throttle Control for details.

  15. Mount the ITB setup to your engine head.  Caution: When assembling the DCOE/IDF/IDA or multiple ITB's to a common Base Plate that incorporates the Coupling, loosen the Coupling bolts before you torque the Base Plate to the manifold, center throttle plates in the closed position and re-torque the Couplings, then set idle! This is in the event the manifold is not truly flat the coupling is not compromised!

  16. Connect Throttle Cable to Throttle Cam.

  17. Connect fuel lines, TPS wiring, and obviously your ECU solution.

  18. Test run the system (use your ECU's instructions).  Get to a point that it idles without stalling so you can test air balance between throttle bodies.  Several methods are available - you can use a length of hose to "listen" for the same airflow between cylinders, you can buy a $15 carb balancer off eBay, or buy a more professional level gauge.  If you find that balance if off, you can loosen the Couplings to adjust individual cylinders.  This can be a time consuming method to use for very fine adjustments, so you may need some idle speed adjusters (contact us for availability).

  19. Install foam air filters around air horns and tighten the clamp.  The filters are designed to use foam filter oil for maximum dust protection.

  20. Enjoy the sound and fury!  Always feel free to contact us with any questions or feedback.

Shafts and Couplings
The Throttle Shafts of the Extrudabody system are designed to be longer than needed for most applications because it's easy to cut them, but hard to add more shaft later. Below is a Typical set of ITBs, the shafts allow up to 120mm of Bore Spacing before extra coupling and shaft have to be introduced. 

If your bore spacing (the distance between the center of each port in your manifold) is between 80mm and 119mm you just need to cut the shaft to length and couple the shafts with a single Shaft Coupling (as in the above pic). This covers IDA, DCOE, and IDF type of Mounting systems. 

If you have more than 120mm Bore Spacing you'll need 2 Couplings and extra length of Shaft cut to fit! This is a typical for the SU style of ITB Set-ups.  
 
Cutting the Shafts:
 
Shafts can be cut with a good quality metal hacksaw, deburring (or rounding) the end of the shaft can be accomplished with a file or a Dremel tool. The shafts should not need to meet in the middle of the coupling.  Shaft do need to be equally inserted into the coupling from both ends, without touching each other.   If the shafts touch in the center of the coupling it defeats the flex of the Coupling itself. 
 
Note: On the side of the Clamp that tightens against the TPS Blade end of the shaft (the flattened end), the Coupling's bolt has to be parallel to the Blade Tip for the maximum amount of Grip! 
Gaskets

Extrudabody provides gaskets (nitrile rubber composite) for all sizes of ITB’s we sell and this is a great solution for sealing most applications.  These gaskets are used between:

  • ITBs and Base Plates
  • ITBs and Extensions
  • Air Horns and ITBs or Extensions

Gaskets for the above interfaces are included as needed with your order.  We do not yet sell gaskets for the interface between our Base Plates and your intake manifold.  These can be found at most retail auto parts stores, or you can use an RTV-type sealant.

In the case of serious racing where one vacuum leak could mean the difference between win or lose, you may choose to hard mount the ITB’s to the Base Plates with RTV-type sealant.  In the case of off-road or high vibration applications, a thin layer of 2 part epoxy can be used to seal and strengthen the Base to Body or Base to Extension to body joints.

TPS

Our TPS is a typical 3-pin unit with Ground, Signal, and 5 Volt Input.  The signal can be used by almost any standalone ECU.  The electrical connector is a Weatherpack-type unit and provided with our Kits and/or TPSes. 

The TPS sub-harness (aka pigtail) is shipped unassembled.  This allows you to wire it to your ECU without having to splice in the wires near the TPS.  Assembly is straightforward and can be done without a specialized crimping tool, although results will be a bit better with a tool.  In either case, you should solder the connection during assembly.

Assembly steps are as follows:  (Refer to the above picture):

  1. Strip insulation on wires about 1/4"
  2. Slide green Insulation Seals into place and slip metal terminal in place (see picture above)
  3. Position wire in terminal as shown above
  4. Hand crimp the Core Wings, then fix with crimping tool
  5. Crimp the Insulation Wings (by hard or tool)
  6. Solder the connection to the right of the Core Wings
  7. Slide each wire into the Weatherpack body until locked in place
  8. Snap the Weatherpack body closed
  9. Wrap the wires with electrical tape, wire loom, or heat shrink tube to secure the wires together.