Mini 1275GT Engine Conversion

Mini 1275GT Resto-Mod, Mar-2018

Converting the Mini to a more modern 16V engine for extra performance. Decided to convert rather than upgrade the venerable ‘A’ series mainly due to cost but also for, hopefully, better reliability and improved driveability via a 5 speed gearbox.

Having studied numerous engine conversions on the forums, I decided to go with a Nissan and soon enough a relatively low mileage CR14DE became available on ebay for a reasonable £280, c/w manifolds and loom.

The 1386cc CR14 is quite up to date – it has, for example, individual electronic spark plug igniters (no distributor), Variable Valve Timing (VVT), “drive by wire” throttle. I haven’t yet found anyone who has transplanted this engine into a Mini, the CG series seemingly more popular. I think the CR14 is larger than the CG range due to the VVT mechanism. Nevertheless, there was clearly plenty of room in the Clubman engine bay, albeit with some tight spots but no worse than an ‘A’ series. The CR14 produces 90bhp in standard form but with some tuning and removal of the cat, I’d be more than happy with 100bhp.

Subframe Fabrication

I made up a rudimentary jig to hold the original subframe so that four key datum points would be fixed in position relative to each other – the tower bolt holes and the front subframe to front panel mounting holes. I decided to locate the lower rear subframe mounts once the near complete modified subframe was fitted to the car and fixed by the tower bolts and front panel mounts. I also decided to retain the rubber mounts for the subframe.

Started the jig by welding the towers to strurdy uprights and arranging mounting lugs to simulate the front-panel mounting holes. Further horizontal members and stiffening gussets were added once the basic structure was in place:

When offering up the engine to the unmodified subframe, it was quite clear that any part of the subframe structure forward of the towers along with the rear cross member would have to be removed. In fact, the suspension towers are really the only parts of the original subframe that are usable. Once the unwanted sections were removed, it was possible to start trial fitting the engine and determining the new structure required, in mostly a “trial & error” process.

The new structure used 30mm x 30mm x 3mm mild steel box section. The build started with the LH engine mount and front horizontal bar (which had to be removeable to allow installation of the subframe from the bottom without major mods to the front panel).

Once the basic structure was complete and with sufficient rigidity to ensure the key datum points wouldn’t move (the tower bolt holes and the front panel mount holes), the jig could be removed and a coat of primer applied:

Prior to finalisation of the basic structure, several trial fits in the engine bay were necessary:

The engine/subframe combination was fitted by lifting the front of the car, wheeling the engine/subframe into the space under the engine bay, lowering the car, then lifting the engine/subframe into it’s final position.

Some bracketry was required for the engine mounts. Here’s the RH bracket that takes a Honda engine mount:

And the RH engine mount in position:

The LH engine mount was a bit easier, just needing a simple adapter plate to connect a Vauxhall Corsa engine mount to the standard CR14 bracket via the large M16 bolt:

It was necessary to modify the tie-rods – slightly shortened and fitted with spherical joints. As the tie-bar front mounts are further outboard than the originals, the tyres now come into contact with them. Not sure yet if this will result in a significant reduction in lock but will need to check on the road. If necessary, can gain some extra lock by putting a bend in the tie-bar and/or adding spacers to the wheels.

Here’s the finished subframe (minus the front bar) with mounting lugs for the engine stabiliser (on the rear lower horizontal), brake pipe fittings, etc.

The engine bay needed some modifications – removal of the upper engine steady bracket from the cross member, relocation of the brake regulator, removal of the LH cooling fan grill & shroud, trimmed RH inner wing, trimmed RH headlamp support and various other mods. Also had to cut-out & fill a recess just above the steering rack to accommodate the cable gearchange brackets.

The engine also needed some modifications. The water pump belt tensioner needed to be cut flush with the water pump and a new tensioner bracket fabricated – see photo below. The CR14 uses a cable gear change and the gearbox mounted cable brackets had to be shortened and re-located to avoid a clash with the bulkhead, although the bulkhead still needed some modification as noted above. Some trimming was also required to the bell-housing to avoid a clash with the steering rack.

Here’s the engine & subframe re-fitted for the last time, unless there’s some serious issues with the installation or the engine/transmission that can’t be fixed in-situ:

The RHS is quite busy with limited space but nevertheless everything is accessible for maintenance. Note the modified water pump belt tensioner – the original tensioner slider arrangement had to be cut and the tensioner wheel relocated further down: