320 to 325 throttle body conversion

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Tools Required

Socket set and spanners

Selection of screwdrivers

Die grinder or drill

Throttlebod 001.jpg

Cylindrical ball nosed burr {a} (Available from engineering suppliers and good tool shops)

A fine file or emery cloth

Degreaser

Confidence

Procedure

Removal

1. Disconnect battery.

2. Remove airflow meter and air filter box.

3. Remove induction hose and idle control valve.

4. Disconnect throttle cable.

5. Mark and remove all pipes from the throttle body.

6. Disconnect the throttle switch connector.

7. Undo the 4 bolts from the throttle body (10mm).

8. Remove the throttle body.

9. Disconnect the fuel feed and return pipes from the fuel rail.

10. Disconnect the blue and brown connectors from the temperature sensors on the thermostat housing.

11. Disconnect and remove the round multi-plug for the injector loom (on the passengers’ side of the block).

12. Remove the inlet manifold support bracket from the top of the rocker cover.

13. Using a ¼” drive 12mm socket remove the 13 inlet manifold to head nuts.

14. Remove the inlet manifold from the head (the centre mounting stud is longer than the rest and the manifold will need a bit of pushing and pulling to get it off).

15. There is a spring loaded crankcase breather tube that locates under the manifold that may stop the manifold from being removed, push down on it and move it to one side.

Modifying the inlet manifold

Throttlebod 002.jpg

1. Using the new throttle body gasket mark the amount of metal to be removed from the manifold.

2. Bear in mind that the bottom of the hole cannot be ground out all the way as there will not be enough material left to make a good seal so leave a 4mm lip between the 5 to 7 O’clock positions.

3. Carefully grind out the manifold to the mark made in step 1. Using the drill or grinder and burr.

4. Using a file or abrasive cloth remove any sharp edges and smooth the hole.

5. Flush the inside of the manifold out with degreaser and lots of water; you don’t want any bits of metal in your engine.

6. Dry completely.

Setting up the Throttle Body

Throttlebod 003.jpg

320i to 325i Throttle Body Conversion

Parts Required Complete 325I throttle body

New 325I throttle body gasket

Inlet manifold gaskets

Induction tube to fit the 325I throttle body and also to fit your existing Idle Control Valve (T or L shape)

Tools Required Socket set and spanners

Selection of screwdrivers

Die grinder or drill

Cylindrical ball nosed burr {a} (Available from engineering suppliers and good tool shops)


A fine file or emery cloth

Degreaser

Confidence

Procedure

Removal

1. Disconnect battery.

2. Remove airflow meter and air filter box.

3. Remove induction hose and idle control valve.

4. Disconnect throttle cable.

5. Mark and remove all pipes from the throttle body.

6. Disconnect the throttle switch connector.

7. Undo the 4 bolts from the throttle body (10mm).

8. Remove the throttle body.

9. Disconnect the fuel feed and return pipes from the fuel rail.

10. Disconnect the blue and brown connectors from the temperature sensors on the thermostat housing.

11. Disconnect and remove the round multi-plug for the injector loom (on the passengers’ side of the block).

12. Remove the inlet manifold support bracket from the top of the rocker cover.

13. Using a ¼” drive 12mm socket remove the 13 inlet manifold to head nuts.

14. Remove the inlet manifold from the head (the centre mounting stud is longer than the rest and the manifold will need a bit of pushing and pulling to get it off).

15. There is a spring loaded crankcase breather tube that locates under the manifold that may stop the manifold from being removed, push down on it and move it to one side.

Modifying the inlet manifold


1. Using the new throttle body gasket mark the amount of metal to be removed from the manifold.

2. Bear in mind that the bottom of the hole cannot be ground out all the way as there will not be enough material left to make a good seal so leave a 4mm lip between the 5 to 7 O’clock positions.

3. Carefully grind out the manifold to the mark made in step 1. Using the drill or grinder and burr.

4. Using a file or abrasive cloth remove any sharp edges and smooth the hole.

5. Flush the inside of the manifold out with degreaser and lots of water; you don’t want any bits of metal in your engine.

6. Dry completely.

Setting up the Throttle Body


1. Set the throttle backstop so that the butterfly plate in the TB shuts completely but does not stick.

2. Set the throttle switch so that the micro switch can be heard to click, it can be quiet so hold it to your ear, it should be set so that it operates as soon as the butterfly plate begins to move. Loosen the 2 screws underneath the switch to turn the switch until it is set correctly then re-tighten.

Refitting

1. Use a cable tie to compress the spring that fits around the crankcase breather tube, fit the spring to the tube and fit the tube into the crankcase.

2. Using new gaskets fit the inlet manifold onto the cylinder head.

3. Refit the inlet manifold mounting nuts and torque to17 Lbft.

4. Using a sharp knife or wire cutters cut the cable ties on the crankcase breather tube spring and locate the top of the tube into the recess on the underside of the inlet manifold.

5. Refit and connect the injector loom multi plug.

6. Refit the blue and brown temperature sensor plugs

7. Using a new gasket fit the throttle body onto the manifold and tighten the mounting nuts.

8. Refit the pipes to the throttle body.

9. Refit the throttle switch connector.

10. Refit the fuel supply and return pipes

11. Fit the idle control valve and the induction tube.

12. Fit the airflow meter and air filter box.

13. Fit the throttle cable and adjust as necessary.

14. Refit the inlet manifold support bracket.

15. Double check that everything is tightened and connected.

16. Refit the battery.

Be aware that removing and re-connecting the battery resets the ECU and upon starting the car the ECU must retune itself, therefore the idle speed may be a little erratic for a while.

Throttlebod 004.jpg

Throttlebod 005.jpg

This article is copy write to E30zone and must not be replicated without prior permission. Written and photographed by Iain Temple (Templ8e30)