|
CROSS - CONNECTION LINKAGE
Shorten the primary or driver lever blade to suit the throttle body mounting centers. Most bodies are delivered with the linkage spring clip already fitted to the secondary lever. If this is not the case, or the bodies are being rebuilt, fit the clip over both primary and secondary levers and capture with the M4 balance adjusting screw and locking nut.
When using the SL1 (extra-short) secondary lever, the anti-rotation tang must be removed from the clip and the clip held straight whilst tightening the locking nut.
 |
BALANCING THROTTLE BODIES
Idle bleed screws (if fitted) should be closed at the start of this operation.
Before starting the engine adjust throttle balance by setting the single idle adjuster screw such that the nearest butterfly is just visibly open, then adjust the cross-link screws such that the remaining butterflies are at a similar angle.
Start the engine and use a flow meter to check airflow through each throttle body bore, adjusting as necessary. It may be necessary from time to time to reset the idle. Always re-check the balance on all bores after each adjustment and with the cross-link adjuster locking nuts tightened. Idle bleed screws (if fitted) may now be used for a final fine balance. Bear in mind that adjusting the idle bleed screws will not affect the throttle position sensor.
If a flow meter is not available reasonable results can be achieved by using a length of small-bore tube to listen to the flow through each bore.
FULL THROTTLE STOP
The butterfly angle when shut is 82 degrees relative to the throttle body axis. The full throttle stop is usually set slightly below maximum and may require adjustment, but bear in mind that many engines give best results at less than the fully open position.
RETURN SPRINGS
The throttle return springs may not be sufficient to compensate for the friction and weight of the pedal and associated linkage, which should be fitted with separate return springs.
FITTING THE THROTTLE POSITION SENSOR (Colvern type)
The throttle pot may be fitted to either end of the butterfly spindle, with due reference to the direction of rotation. Place the clamp over the pot and tighten in a central setting. After fitting, eliminate any residual side load on the spindle by one of the following methods;
Either hold the butterflies slightly open (eg. a 1mm gap under the butterfly) and lightly tap the opposite end of the spindle, or tap the end of the throttle pot with the butterflies tightly closed. A plastic screwdriver handle is the ideal weight and hardness for this. Ensure that the butterflies close positively with no signs of extra friction.
FUEL RAILS
It is best to ensure a constant fuel flow through the rails with no 'dead end'. Feed fuel in at one end, through each fuel rail and out to the pressure regulator from the opposite end. For very high flow applications such as large 8 or 12 cylinder engines, or when using alcohol based fuels, split the system into two or more circuits e.g. by feeding fuel in at two opposite ends and then to the regulator through a central 'T' junction.
Some injector types differ slightly in length. Check that both injector 'O' rings remain fully engaged with their respective bores under all conditions, with retaining clips in place. Shim or shorten fuel rail mountings if required.
ASSEMBLY
The twin-body fuel rail is supplied part assembled and requires the included interconnection pipe to be cut to length as follows:
| 1) |
Measure the center distance between the two throttle bodies, e.g. by measuring from the front edge of no. 2 to the front edge of no. 4 bore on a four cylinder. |
| 2) |
Subtract 107mm from the above figure. |
| 3) |
Cut tube to the resulting length, ensuring that ends are clean and square |
| 4) |
Carefully chamfer ends at 15 to 30 degrees for a distance of 1 - 1.5mm. Ensure that there are no burrs or snags which could damage the 'O' ring on insertion.
This step is most important - poor preparation will result in leakage. |
| 5) |
Lubricate ends of tube and fuel rail bores with light oil or other suitable lubricant. Insert tube. |
Note: The connecting tube is retained by the fuel rail fixing to the throttle bodies and the fuel system must not be pressurized with the rail unrestrained and free to move apart.
|
Failure to follow any part of these assembly instructions
may cause fuel leakage and
a resultant risk of fire.
MOUNTING
The fuel rails are supplied with spacers to accommodate different lengths of injector.
Use the supplied spacers with standard length injectors.
For short injectors, e.g. 'Pico', no spacers are required.
Other lengths of injector may be accommodated by reducing the spacer length to suit. Ensure at least 0.5mm of end float when an injector clip is fitted.
Ensure that the connection pipes are correctly mounted and do not pull tight with engine movement. Spigot-ended fuel rails are only 8mm diameter under the hose - insufficient to restrain an engine without breaking!
OPTIONAL FUEL PRESSURE TEST VALVE
The test valve is a standard Schrader product and suitable test equipment is available from Schrader or their dealers.
SERVICING
Maintenance is not normally required beyond normal adjustment and cleaning. However, if the throttle bodies are dismantled, note the following points;
Remove butterflies and spindles before removing the spindle seals, which may then be carefully 'hooked' out. Be careful not to turn the outside edge of the seal back when refitting.
The spindle bearings may be removed by partly inserting a 3/8" UNC taper tap or similar and then turning and pulling simultaneously. Discard removed bearings. Take care not to insert the tap beyond the bearing and thus into the casing.
Only replace bearings and seals with original Jenvey parts. Do not use industrial alternatives.
Spindle covers (if fitted) may be removed by collapsing inwards using an 8 to 12mm diameter drift. A new cover must be pressed in and flattened using a 28mm diameter tool, supporting the body directly underneath.
Use Loc-Tite Nutloc on the butterfly screws when refitting. The projecting screw threads may be deformed for added security, but spindle damage may result when the screws are next removed.
When refitting spindle levers, ensure a gap of 0.3 to 0.5mm between the closest part of the lever and the body side when the butterfly is firmly closed.
|
