Engine transplants - Changing FDs and speedo drive ratios.

What they don’t tell you in the manual! Terminology - FD - Final Drive (diff ratio) What they don’t tell you in the manual! If you’ve decided the FD fitted isn’t what you want, changing the FD is possible without separating the engine from the gearbox. Removing the diff case will allow you access to the diff assembly to change the crown-wheel, and access to the gear-change linkage. Use a manual for crown-wheel replacement. While you’re in there it would be just as well to replace the thrust washers and diff-pin as these are the source of many a gearbox problem. Particularly for up-rated engines where fitment for the competition diff-pin is highly recommended. Once again, follow the manual here. Now the bit they don’t tell you how to do... Rod-change types - Removal of the speedo drive housing gives access to the pinion retaining nut (1.5”AF socket needed and a long bar). To be able to undo the pinion nut (torqued up to 150lb ft !!) you need to engage two gears - 2nd and 4th - t

Electronic Speedo and Sensors

More and more people are building highly modified Minis, some with engine conversions, others fitting items such as the Mini Spares 8 Port, all these parts can make fitting a speedo cable drastically difficult, and with limited availability of the correct combination of speedometer worm....

Engine - 1098, Initial Tuning

The 1098 (1100) engine has had a lot of bad press over the years - largely because of early experiences when trying to tune the motor brought about problems with the then standard components available - they simply were not up to taking any real punishment as experienced in racing.

See bottom for useful part numbers.

This fallacy was handed down generation to generation like some scary bedtime story. Those that have used the unit in more recent years, employing more capable componentry know what a demon motor this can be. Following is an initial look at what it will do with a little modification - the results compared directly with it's smaller brother the 998 for illustration of the potential.

Abridged History
When the Mini was first conceived it ustilised a de-stroked version of the then quite remarkable 948cc A-series engine.

Gearbox - Fomulae for FD/Tyrespeed and Gear Ratio Calculation

Basic rule to remember is ratio is established by dividing tooth count ondriven gear by the tooth count on its driver. To work out overall gearbox ratios you also have to establish the constant ratio.

Terminology -
FD - Final Drive (diff ratio)

Formula : 60,000 FD (Final drive/diff ratio) x wheel rev per mile.

Calculation for establishing vehicle speed for different final drives.
Formula These are for common tyre types, and accurate enough for assessment - a combination of using industry standard for theoretical calculation, actually measured assortment of wheels/tyres, and calculated averages! Applying

Engine transplants - Ancillary parts

Engine mountings are a whizz to fit as the Mini ones fit straight onto any of the other units. Just remove the Metro/AA/1300GT ones and swop the mounts over from the Mini unit. If they’re split, fit new ones, they’re cheap.

Terminology -
BBU - Big Bore Unit
SBU - Small Bore Unit

NOTE: This information covers transplanting large-bore engine units into small-bore engined Minis. For further information for exact differences between pre-A+ and A+ units, see relevant separate article.

Engine mountings and steady bars.
Engine mountings are a whizz to fit as the Mini ones fit straight onto any of the other units. Just remove the Metro/AA/1300GT ones and swop the mounts over from the Mini unit. If they’re split, fit new ones, they’re cheap. If using the AA/1300GT unit - it's advisable to cut off the 'wings' on the front plate that carried the engine mounts on the radiator end.

Engine transplants - gearbox information

A subject worthy of an entire book to explain the whys and wherefores, and also causes much consternation on the part of the transplanter. Terminology - BBU - Big Bore Unit SBU - Small Bore Unit FD - Final Drive (diff ratio) A subject worthy of an entire book to explain the whys and wherefores, and also causes much consternation on the part of the transplanter. Much confusion’s spread over which gearbox has the best ratios, is best to use, and with which FD. For a detailed account on this and covering all gearboxes fitted as standard to the Mini, see the relevant separate articles 'Gearbox - Standard production gearbox types'. Fortunately, when selecting a complete engine and gearbox unit from a Metro, the gearbox will pretty much suit the engine and be easily transplantable whole into the Mini. It shares exactly the same rod-change linkage as the Mini. Difficulties only arise when fitting a rod-change gearbox into a pre-1973 Mini that has the old remote-type gear-change mechan

Gearbox - Formulae for FD/tyre size/car speed and gear ratio calculation

Calculation for gear ratios and transmitted engine rpm Basic rule to remember is ratio is established by dividing tooth count on driven gear by the tooth count on its driver.

Basic rule to remember is ratio is established by dividing tooth count ondriven gear by the tooth count on its driver. To work out overall gearbox ratios you also have to establish the constant ratio.

Terminology -
FD - Final Drive (diff ratio)

Calculation for establishing vehicle speed for different final drives.
Formula :                               60,000 
                    FD (Final drive/diff ratio) x  wheel rev per mile.

Mini Production dates

We have tried to get together as complete list as possible to show all the models made from 1985 onwards, hopefully this will help identify those cars that have been modified over the years. If you have any information that you know is correct or anything that you think is not right please let us know.

5 SPEED GEARBOX DISMANTLING SHEET

Your 5 speed gearbox has a special 5th gear, laygear, and reverse idler shaft assembled with a modified gearbox main case and a different speedo end casting.

These parts must be removed before the main gearbox cluster can be removed. When a clean work area has been prepared, the removal of the 5th gear and laygear is as follows.

1. Remove the new speedo end casting assembly with the two bearings. These are a slide fit in the casting and are not positively retained.

2. Remove taper bearing No LM11749 off the 5th gear shaft along with the needle roller bearing carrier from the bore of the 5th gear, leaving the gear loose on the shaft.

3. Remove diff and housing as per workshop manual, turn the selector rod at base of diff housing area anti clockwise-and with the spool pull out as far as possible...

Historical Article - Nov 1991 - Twini Mini

The front brakes are standard Cooper 'S' 71/2" variety with the standard drums on the rear, with the assistance of a servo the rear regulator valve has been left out of the system and the brakes work very well. As the weight of the second engine amounts to the equivalent of two 11 1/2 stone passengers. Rear cooling is taken care of using a 1300 radiator mounted in the standard position. The heater take offs are connected to a 19 row oil cooler.

Historical Article - Nov 1991 - Twini Mini

The front brakes are standard Cooper 'S' 71/2" variety with the standard drums on the rear, with the assistance of a servo the rear regulator valve has been left out of the system and the brakes work very well. As the weight of the second engine amounts to the equivalent of two 11 1/2 stone passengers. Rear cooling is taken care of using a 1300 radiator mounted in the standard position. The heater take offs are connected to a 19 row oil cooler.

Historical Article - Nov 1991 - Five Speed Gearbox

For years people have complained that the Mini required a fifth gear. Although many years ago the idea was tackled by Felday, Coletti Francis and Jack Knight, these gearboxes suffered through being either too complex to make, awkward gear changing or poor reliability.

Historical Article - Nov 1991 - Five Speed Gearbox

For years people have complained that the Mini required a fifth gear. Although many years ago the idea was tackled by Felday, Coletti Francis and Jack Knight, these gearboxes suffered through being either too complex to make, awkward gear changing or poor reliability.

Historical Article - March 1992 - MANIFOLDS

A desire to solve induction installation problems and assist in the choice of induction types for many ‘A’ series applications, led to the production of a new range of Manifolds from Mini Spares, London, to mount on the ubiquitous SU carb of various types and sizes.

Despite numerous manifolds being available from many different sources, there seem to be three times as many problems when...

Historical Article - March 1992 - MANIFOLDS

A desire to solve induction installation problems and assist in the choice of induction types for many ‘A’ series applications, led to the production of a new range of Manifolds from Mini Spares, London, to mount on the ubiquitous SU carb of various types and sizes.

Despite numerous manifolds being available from many different sources, there seem to be three times as many problems when...

Historical Article - May 1993 - Five Speed Gearbox

FIVE SPEED GEARBOX - DRIVING IMPRESSIONS

Having given the updates in development and supply expectations of our five speed box, it has come into fruition. Customers worldwide have been receiving their long awaited gearboxes. The feedback has been very good. Odd teething problems have occurred, but more due to the "if all else fails, read the instructions" attitude of those suffering the odd problems. The demand is so high for our five speeder that I have had to wait my turn before I could fit one to my MG Metro. Sorry it's not a Mini, but it's my "utility" vehicle.

Well, what can I say? It would be very easy for me to be totally biased towards our own product, spawned by the genius of Dave Hirons, and manufactured by his gear manufacturing company Tran-X, so I will. I couldn't believe how right it felt. T...

Historical Article-February 1995-Cooper body shell

Cooper Body Shell The Heritage specialists fit a shell at the Classic Car show at the N.E.C. Only the latest type production bodyshells are available from Rover, who in their infinite wisdom have reduced the price from £1 ,700 to £950, which may help keep a few more cars on the road.

Historical Article-February 1995-Cooper body shell

Cooper Body Shell The Heritage specialists fit a shell at the Classic Car show at the N.E.C. Only the latest type production bodyshells are available from Rover, who in their infinite wisdom have reduced the price from £1 ,700 to £950, which may help keep a few more cars on the road.