Rover SD1 Forum Snippet #16 - Mods Wot I Dun to My Twin Plenum

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Randomly on the SD1 Club Forum, information appears about modifications to our cars causing purists to choke on their demands for originality.

Street racers go even further beyond the pale, but somewhere below the threshold many useful modffications appear that enhance safety, improve drivability, upgrade performance, substitute NLA components or just simply improve functionality.

Here are some made over the years having the distinct merit of subtlety, combined with funtional improvement..

So to details of the mildly modified Twin Plenum Vitesse D330 ENH and others made to a Vdp Efi. Next time you see this car ask for a demo and be amazed at their simpldpity and effectiveness.

# Uprated Tail Lights. This is to replace the 21 Watt Stop Light bulbs with 21/5 Watt Stop/Tail bulbs and at the same time change the 4 Watt Tail bulbs to 5 Watts. This raises the overall Tail Light power from 8 Watts to 20 Watts. A very worthy safety enhancement given that the original Tail Light visibility was so poor compared to more modern vehicles.Full details of the modifications can be found here;

# Uprated Brake Lights. This modification uses a relay activated by the Brake/Stop Light supply voltage to illuminate the Rear Fog Lamps as additional Brake Lights. The circuit allows the Fog Lamps to still function normally, including the dashboard fog lamp warning bulb, without activating the Brake Lights. Likewise when the brakes are applied the dash fog lamp warning remains off. The overall effect is to raise the total Stop Light power from 42 Watts to 84 Watts.

There is a legal issue regarding Rear Fog Lamp beams being activated during normal driving conditions but one might weigh that slight criminal risk against the unmissable indication to any following vehicle that the car is stopping NOW. Thus, the risk of suffering a rear-ender is considerably reduced. At MOT time, the modification is easily deactivated. Full details here;

# Uprated Front Indicator. This cute little trick implants a separate 5 Watt Tail bulb holder in the metal casting behind the front indicator lens' to improve side visibility of the front turn indicators.

With the monkey-metal indicator casting removed from the front wing, drill out the small round platform towards the rear of the casting to receive a regular tail light bulb holder. Fit the holder and add a wire from its live contact to the existing 21 Watt bulb holder and refit the modified assembly to the front wing. No earth wires are required.

The beautious effect considerably improves side visibility of front indicators to traffic approaching from either side, say, for example at a tight "T" junction or exiting from a domestic driveway.

# Twin Plenum Cruise Control.. This optional extra was not offered with the Twin Plenum Vitesse but it is possible to transplant a Hella GR65 Cruise Control System from an SD1 Vdp Efi with only minor modifications to the vacuum actuator bracket, throttle quadrant and pull rod. All other items are as per the original Vdp Efi specification but with an extra vacuum dump valve/switch fitted to the clutch pedal. The vacuum actuator has more than adequate force to operate Twin Plenum Throttle Quadrant and to overcome the three throttle return springs fitted to that system.

If one fancies Cruise Control on a Twin Plenum Vitesse, this is a worthwhile and challenging project that really works. Full details of how to undertake the whole nine yards can be found here:

# Substitute Throttle Pot. The original SD1 Efi Throttle Pot became unavailable during the mid 1990's where-upon, erstwhile Rover SD1 Club Technical Director, Carl Heinlein, came up with a substitute system for the single plenum cars which I then further refined for the Twin Plenum.

It uses a RadioSpares/Electromail Rotary Position Indicator (p/n 319-310) on a fabricated mounting plate to replace the discontinued item. It also had the merit of being a low cost conversion, less than £25, if done on a DIY basis.

Full details of the process including other methods of repair and replacement can be found here:

# Air Conditioning System - “ON” Indicator. To monitor the performance of the later Rover SD1 CCOT A/C system in terms of functionality, connect a wire from the compressor clutch live feed to the redundant Diesel Glowplug Lamp in the dashboard warning lamp cluster. It requires a degree of wiring skill/ability and reference to the appropriate circuit diagram for the model involved.

For the late Efi model, splice a connection into the Light Green (LGR) CCOT clutch feed wire at the engine multiplug below the coolant expansion tank and feed it along the wing, thro' any existing bulkhead grommet into the cabin, then upwards into the instrument cluster, to connect with the Diesel Glowplug Lamp unused contact on the ribbon connector under the binnacle cover.

The lamp illuminates in sympathy with clutch/compressor activation and {improbable as it may seem) by monitoring the on/off cycle time and its mark-space ratio its easy to assess if the A/C system is working correctly. Sure, an understanding of the rudiments of the A/C system is helpful, it's not rocket science, just simple refrigeration, details of which can be found here:

Substitute Efi Throttle Pot to overcome non-availability

# Twin Plenum Intake Hoses. Fabricate low cost replacements from 3” bore corrugated fabric, spiral wound hose with close fitting cuffs made from a motor cycle inner tube, in lieu of very expensive original replacement items, when available. Here is the finished product. Click image to enlarge.

See the specially fabricated Rover SD1 Twin Plenum IntakeHoses.

# Side Rubbing Strip, Chrome Stripe Restoration. A very effective home brew renewal of Chrome Stripes that sadly fade over time, using a readily available sticky tape from www.flints.co.uk The process requires a fair degree of care, sharp scalpel blades and extreme cleanliness.

It's easier if the rubbing strips are off the car, but quite do-able if not. It even works for the chrome door card interior decoration too. Not perfect but a definite improvement to tatty door cards. Full details of the process are available here:

# Rear Light Cluster Repair - Fixing Bolt Retention. When light clusters are removed from the rear panel, two common problems emerge, Fixing Bolts fall inside the housing and subsequent Water Leaks upon refitting. For the former, fiddle the wayward bolt into its correct location and from the outside, grip the thread with needle-nose pliers, wind several turns of thin soft-iron plastic covered garden wire around the base of the threaded section and close it with a twist. Add a touch of araldite to the wire/bolt/plastic junction and allow to dry. Viola!

Tricky alternative. Hold the inserted bolt in position with some rubber tube slipped over the thread and drip some araldite onto the bolt head and its recess from inside the bulb cavity. Yes! Tricky!

# Rear Light Cluster - Water Leak Solution. Upon refitting, water leaks are a pain, even with new gaskets. Obtain a sealant specially formulated for traditional windscreen fitters from a local factor and run a continuous bead around the gasket (panel side) before closing. It's graphite black, non sticky and doesn't set. As the fixings tighten, the goo spreads into all the crooks and nannies for a superb water-tight seal. Remove any squeezed out excess with white spirit. The real beauty comes much later upon removal. Unlike silicon, this stuff is a cinch to rub off with hardly a trace.

# Tame a Nasty 5-Speed LT77 Manual Gearbox (with an unusually radical cleaning process). My Vitesse used to have a truly nasty gearbox. It baulked at will and was notchy to a fault. In fact it was very, very hard work. This was my last resort. Basically the gearbox was flushed out with a mixture of ATF and White Spirit and refilled with Mobil 1 Fully Synthetic 0W40 viscosity engine oil and a dose of Molyslip Gearbox Treatment. The transformation was miraculous: Read all about it here:

# Aid to Radiator Cowl Removal. The lower brackets are effectively blind making it difficult to turn the fixings. Starting from the front of the 2 big round holes in the belly pan, use a padsaw to cut 2" square access holes toward the front, in line with the brackets. Use a 3/8" drill for the four forward corners of the cutouts before sawing to prevent future stress fractures. Result,? Very easy access!

# Aid to Central Locking Relay Removal. Modify Series II front door inner panel by drilling two 3/8" screwdriver access holes dead in-line with the relay fixing screws. Many knuckles will be spared injury. Deburr and repaint the hole edges to avoid future corrosion.

# Aid to Door Handle Removal/Refitting. Without self rotating spanners and baby's hands, refitting door handle brackets is a triumph of luck over inaccessibility. As above, drill two 3/8" nut-runner holes in the sloping face of the inner door panel in line with the bracket fixing nuts. Seemples!

# Anti-Stall Modification for Efi Auto. Some Rover SD1 Efi Autos cars habitually stalled in post production when put into Drive/Reverse due to the load applied by the Torque Converter/ Transmission. For customers who complained, Rover offered a retrofit to enable the starter inhibit switch to signal for additional air to the plenum to prevent the problem., Read all about it here:

# Habitual Coolant Loss Workaround. Over time, often due to poor maintenance, Rover V8 Cooling Systems became notoriously difficult to manage resulting in recurrent loss of coolant. Causes are various, not always easy to trace but include small, almost insignificand, head gasket leaks over-pressurising the system. As expected the pressure cap releases small amounts of coolant on each trip necessitating frequent top-up. By clever placement of a 500 ml plastic bottle on the chassis rail below the expansion tank and routing the drain tube into it, expelled fliuid is caught and saved, to be sucked back into the system when the engine cools. Magically, by adding coolant to the bottle it enables automatic top-up too. Lots more on this and cooling systems here:

# Conclusions. Some of the above ideas and fitments including development of a working process are (AFAIK) original. Mostly tho', they emerge from round table or forum discussions triggering possible solutions to long standing mutual problems. Others are copied from fellow owners or lifted from magazines/web pages. Of the great truism "There is nothing new under the sun", it can not be wholly true can it? After all we've all had our own "eureka" moments and in applying them successfully, we deserve at least, perhaps, our own "fifteen minutes of fame".

If any of the above appeal to you, then please jump in and apply them to your personal needs. There is no copyright pending! On the other hand if any SD1 owner has applied a similarly clever or subtle idea to their car and would like to share it, why not write it up for publication in the club magazine, Alternatively, I am more than happy to append it to these pages under your name.

The SD1 Efi Diagnostic Challenge Continues

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Ramon Alban


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