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Brake servos first made an appearance on Falcons late 1965 with the Girling
AHU 689, fitted along with front disc-brakes, as standard equipment
to the Fairmont and also available as an option on the Hardtop Coupé. If you don't already have one of these units they are very hard to
find and the repair kits are extremely expensive, around $150. The VH40
series on the other hand are commonly use on a number of Australian
vehicles, with the minor repair kit costing approximately $30 and the
large Diaphragm if required is about $40. Plus it will fit neatly under
the off- side front guard keeping the engine bay clear and looking original. While the most likely time to add a booster will be when fitting disc brakes,
a servo can also improve braking with drums. Without having to alter
the complete system controlled handling can be maintained if the servo
only operates on the front brakes. It's important to allow plenty of clearance between the unit and the front
wheel. Cheek from lock-to-lock as well as full up and down movement
of the suspension. All the brake and vacuum lines must be anchored to
the vehicle body. The VH40 also has an equalising air vent with a filter covering it. This must
be extended to a part of the vehicle where dust free air can enter the
unit. Start by removing the radiator grill, the off-side headlamp surround and front
guard. Mount the VH40 with the air vent facing up and the drum end lower than the
other. This will keep the air inlet extension clear of the wheel and
also make it easier to bleed the unit. |
Make sure the pipes are well fixed to the vehicle body
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The air vent can be extended with a length. of 50mm aluminium flexi-pipe. This can be obtained from accessory shops and is used on models like the XD between the air cleaner and the exhaust pipe.
The flexi-pipe is attached to the radiator support panel with a piece exhaust pipe which is forced into a 50mm hole. While at the other end a piece of 5Omm PVC pipe is softened by heat and pushed over the filter housing on the VH40. Use a length of 10mm copper pipe to extend the vacuum line along
the engine bay side wall. Either end is connected with a suitable
length of rubber tube to the manifold and servo. The photo below shows
the booster outlet brake fluid pipe exiting from the end of the booster
it was in fact easier to bleed the system with the fluid outlet in
the side exit and the bleed screw in the end hole as shown in the
diagram above.
The brake line across the firewall will remain. While the three way junction that feeds the near-side front and rear wheels has to be replaced with an inline junction, feeding just the rear. Disconnect the off-side front brake line at the brake light switch junction on the firewall and remove both front brake-line pipes. |
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The location of the VH40 and the vent pipe to the radiator support panel.
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Re-locate the three way junction to the sub-frame at a point directly below
the servo. Run new copper brake line around the front of the radiator
support panel to the near-side wheel. Other pieces are also run
to the off-side wheel and servo outlet. The servo inlet is connected
to the vacant hole at the brake light switch junction. Some
States will not allow copper, check first. Have someone in the trade swage the old gland nuts to the new pipes once they
are cut to length On XP’s remove the union between the master cylinder outlet pipe and the master
cylinder itself and discard the non-return valve located there.
On earlier models remove the non-return washer from the inside
of the master cylinder. If your not sure about what to remove
have someone in the trade to do it for you. Re-assemble and bleed the whole system. Road test and re-fit the guard etc.
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DISCLAIMER While this method has been tried and works, NO responsibility will be excepted by the author, the Club or any of its Members.
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