After joining the two half's together you loose the mounting holes for the extra air valve on the back of the plenum. I fabricated a plate and had it welded to the rear face after cleaning up the joining weld.
The throttle linkages were surprisingly easy to sort out. Rover had made a certain amount of symmetry in the throttle housing mountings allowing the throttle potentiometer plate, butterfly rod and springs to be reversed. While with a small amount of cutting and welding the opposite throttle bracket can be reversed and mounted on the three bolts that held the throttle potentiometer plate. Basically I cut the mount in half, lined up the two upper most holes with the two upper most bolt holes. Flipped over the rod carrier plate, drilled a third hole to use the lower left bolt hole and welded a washer around the engine breather pipe inlet to reinforce this area.
Picture shows original mount left and modified mount right
The throttle cable pulley wheel mounted under the left housing pictured below already had a hole for operating the right hand modified throttle arm in the correct plane. Rover seem to set it up for the job, maybe they were experimenting along the same lines, who knows! Two new stainless actuator arms with adjustable rose joints link the whole lot together. Sounds too easy!, only time will tell!
Extra actuator arm on the right.
The throttle cable pulling plate shown central on picture above only required a small cutout to clear the second actuating rod. This unit has been lowered as per method 2 of my modifications, without the reduction this cut out would not be required.
The opening of the second butterfly has been mechanically delayed, so the first opens 1/4 travel then the second opens at a higher rate to both be open at full throttle. This stops the second butterfly opening momentarily before the primary potentiometer sends a signal to the ECU. This also cuts out balancing issues at tick-over as the secondary throttle stop and air screw are closed, so I only have to adjust the primary.
This was achieved by having machined a stainless pot and piston that replacing part of the secondary actuation rod. The piston pushes against a spring in the pot till the spring bottoms out then the rod moves as normal. The spindle arm rod was shortened to increase the opening rate.
Below is an aerial view of the modified right hand mount, showing reversed spring positions and new spring retainer machined from bar, mounting off the 3/16 UNF mount plate fixing.
The new fuel rails use a feed-pipe cross-over system to reduce the angle of bends in the flexible hoses. Due to the limited room on the new rails from having moved the injector feeds outboard of the throttle housing overhang, I fitted separate "T" piece fuel fittings for the inlet and outlet at each end of the plenum. Mounting the rails off the existing injector retaining plate bolts works nicely keeping the pipe work out of the way and avoids chafing of the flexible hoses that may occur if the pipe work is floating.
These injectors are the older flapper type. I have since upgraded to the later hotwire injectors, which can be modified to fit in the same setup, by removing the fuel rail "o" ring and associated plastic to reveal a push on connector underneath. You can then mount them in the earlier flapper type clamps and using a hotwire manifold, tap out the associated mounting holes, of which some are blanked off on the later manifolds.
I decided to port match the inlets, using a tin plate style valley gasket as a template I took the port size out to the maximum gasket hole size. I will port the heads to match in the near future.
On final inspection the left hand/higher mileage side was found to have play in the butterfly and throttle linkages. A quick visit to my local Rover dealer and two replacement bushes, one spherical bearing and a new butterfly spindle was ordered, cost £20. The spindle was the wrong item, probably off a later model, but fortunately the only difference was the throttle potentiometer end was shorter, which was just what i was looking for, for the right hand side, as only one potentiometer was to be used on the left.
I have chosen to run complimentary twin air filters, mounted ahead of the radiator to take advantage of the cooler and at high speed, slightly pressurised air. The following photo shows the twin 3 inch air feeds which pass the radiator outboard of the inner wing.
The
3" feeds through inner wings
and had to be reduced to 2" aside in this area to clear the tyres