GUIDE FROM 16VMINI CLUB - ALL THE SUBFRAME WORK IS DONE AND HAS BEEN FITTED TO MY MINI
Frames and Installation
There are two main paths for frames when fitting these engines to minis, the metro frame or the modified mini frame. There are advantages and disadvantages to both of these and you need to think carefully before choosing which route to take. Firstly choose you final engine/gearbox combination as this can determine which frame you use. Generally using the R65 gearbox allows you to use a modified mini frame and the PG1 require use of the metro frame as it is larger.
Metro Frame
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This is by far the easiest route to take, the advantages are you can use standard rover proven parts, build up the complete assembly and basically drop it into the car with bigger brakes, stronger suspension, bigger bearings and bushes and everything is easily and cheaply replaceable with stuff found in a scrapyard. The disadvantages are you loose the standard mini front, need to use metro offset wheels and Watsons spacers on the rear. If you are using the R65 gearbox you will need a complete metro frame and can use the metro engine mounts, driveshafts, hubs, wishbones etc as a complete unit. If using the PG1 gearbox then you will need MGF subframe arms (where the engine/gearbox mounts sit), mgf driveshafts, with metro hubs, brakes, wishbones and top arms. If using a metro frame you will also need to weld on a lower engine steady at the rear of the frame. The easiest option for the pg1 gearbox is to pick up a complete mgf rear subframe and swap some metro hubs, wishbones and top arms to it.
Mounting the frame is relatively straight forward. You will need to make (or buy) two side plates which bolt onto the towers of the subframe and then to the damper mounting points on the mini (between 4-6mm thick steel). You will then need to make mountings for the rear of the frame to the mini floor, this can be either 2” box section steel welded to the frame with a flange welded to the end to sit against the floor of 6mm thick steel plate bolted to the underside of the frame to the underside of the mini floor if you can’t weld. It is also a good idea to reinforce these areas of the mini floor with extra steel either welded to the outside of the floor or on the inside of the mini with the mounting bolts passing through.

(note rear lower mountings welded on)
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(shows side plate, coilover suspension and brake pipe routing)
Gear linkages can be taken from the metro in the case of the r65 box and the two rods can be cut down and re-welded to position the lever correctly. This is pretty straight forward. If using the PG1 then you will need to source a linkage from a PG1 equipped car and again cut down and re-weld the rods to suit.
With the metro frame you can use the standard k series exhaust manifold and downpipe then weld or clamp your mini 2” link pipe to it, it lines up pretty well!
The brakes will need sorting out as the flexi unions are metric and no doubt your mini ones will be imperial so new copper pipes will be required. You will also need to fit minivan rear cylinders to stop the rears locking up.
If you are using the Watsons subframe you will be supplied with mountings and suspension springs so everything bolts together nicely. If adapting your own frame then you will need to use mini coilovers with between 400 – 550lb springs. You can use the mini coilover type top mounts but will need to fabricate the mounts on the top arms to replicate the mini type coilover brackets.
Using the metro frame will require the use of an extended round nose or clubman front. You will also need to modify either the front bar on the subframe or the valance to clear it.
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(metro frame with MGF engine/gearbox mounts and driveshafts, mpi mini radiator)
The fuel system will have to be modified to run the injection system unless you’re converting a later MPI mini. If you have a saloon then you can simply fit the mpi fuel tank and run two fuel lines to the engine, if a van or estate etc, you can either try and fit a injection pump (from any k series mpi car) into the tank or fit an external injection pump and plumb in a return pipe.