GEARBOX - Up-Rating Drop Gears

The standard drop gears are fine for practically all road use - almost irrespective of power output. part numbers: DAM9373, C-STR123, C-STR124, C-STR30, C-STR30A, C-STR30T, C-STR30TA, C-STR230, C-STR240, C-STR250 Terminology - Drop Gears - Transfer gears (primary, idler and input gears) Large-bore - Refers to anything based on a 1275-type unit Small-bore - Refers to anything based on 850/998/1098 units Despite what many folk believe - they are more than strong enough, and will perform perfectly well if correctly set up. That means getting the idler and primary gear end floats right, and using new bearings for the idler gear at each re-build. Simply following the methods outlined in the relevant workshop manuals will achieve these simple goals. There are two problems with standard drop gears - the main one is the helical cut of the teeth, the other a very limited selection of ratios. The helical-cut teeth are essentially power absorbing - both from increased metal-to-metal c

GEARBOX - Limited Slip Diffs; necessary parts for installation.

Fitting an LSD isn't as simple as replacing the diff cage unit. In all cases a certain degree of diff housing modifications is needed - material needing to be ground/filed away to provide clearance for larger diff housing cases and crown wheel bolts. Although it has to be said the Quaife diff is supposed to fit without these mods. I've never found that. The design and manufacture of the LSD to facilitate any other function other than that of a standard 'open' diff assembly precludes use of standard CWPs. So one suitable for an LSD is needed. Naturally Mini Spares/Mania supply these in an extensive range of FD ratios. The output shafts are also different. A much thicker spline type is used within the LSD assembly. Consequently a suitable pair of LSD-compatible output shafts are needed. Some folk still insist on running the archaic, power consuming Hardy-Spicer type driveshaft to diff joints - although this is the only real option for rallying unless a change in driveshaft assembly

Gearbox - Common Sources of Problems

Seems recently a number of folk have been suffering gearbox failures of various sorts; nothing new there then except they've popped their heads up over the parapet to ask why. part numbers: C-22A1738, C-22A1731, 88G396, CHM141, 13H9513, 22A611, 22A610, TSP100390, TSP100400, 22G2595 Under closer scrutiny this time around the reasons for bearing failures, gear tooth breakage, and jumping out of gears to name but a few are the sources of hassle. Just like in engine building, a gearbox needs careful and proper attention when building it up. It isn't a difficult job, and most competant DIY mechanics can make a decent job of it. But, just like engine building, it's the knowledge of what to look for prior to and during the build that sets the 'professional' builders apart. Hopefully resulting in a more reliable, perfectly functioning unit. One generally over-looked, or completely missed, feature is where the layshaft is carried in the gearbox casing itself. The shaft merely runs in tw

Super Mighty Minis Championship. Rounds 2 and 3.

Brands Hatch was the latest venue to host round 2 and 3 of the Super Mighty Minis Championship in 2003. On a gusty Easter Sunday morning I qualified 8th I could have done better, but I was still getting to grips with the first corner – the infamous Paddock Hill Bend...

Idler Gear - Setting End Float

A fairly crucial part of how the idler gear operates is its tolerances and running clearances. part numbers: 22A1545, 22A1546, 22A1547, 22A1548, 22A1549, DAM4822, DAM4823, DAM4824, DAM4825, GUG705563GM, AAU8424, ADU6033, CCN110, 2A3643, 22A152, 53K547, Terminology: DTI - Dial Test Indicator End float is a continual problem as folk either ignore it through ignorance or lack of accessible information on how to do it, or belief special tools are needed. Also, later factory assembled engine units (from about 1992 onwards) were built up using whatever shims and thrust washers were available, since Rover were not making regular orders for all shim/washer sizes due to the forthcoming end of production. Consequently, many units left Rover with incorrect (usually too big) clearances. The idler gear was no exception. Too tight a clearance and the idler gear will either seize solid when it gets hot, or destroy the thrust washer thrust faces in the comparably soft aluminium gearbox and t

Gearbox - Up-rating diffs and FDs

There’s a good selection of straight-cut final FDs available. Examine the FD table, and using information from

'Gearbox - Final dives, standard' and 'Gearbox - Formulae for car speed, etc.'

you can assess which would best suit your usage. Bear in mind that they’re noisy, make sure you select one that’ll fit your diff unit, and also consider that using drop gears will allow fine-tuning of the ratio where necessary. See

'Gearbox - Up-rating drop gears'

Gearbox - Up-rating diffs, FDs and ancillaries.

part numbers: C-BTA166, C-BTA167, DAM6624, BTA101, 2A7062, DAM5071, DAM6027, RPS1418, C-AJJ3385, C-22A1731, ...Read more

GEARBOX - Syncro vs 'Dog' engagement

NOTE

; A 'high' or 'low' ratio gear is in reference to it's performance, not it's numerical number. To illustrate - a 'high' FD ratio will give 'higher road speed', but will have a numerically low figure. A 'low' FD ratio will give lower road speed, but have a numerically high figure. part numbers: C-AJJ3371, C-AJJ3319, C-STN39, C-AJJ4014, C-STN76, C-STN77 A by-product of this will be reduced acceleration capability on the 'high' ratio, increased acceleration capability on the 'low' ratio. The main gearbox gears work in the exact same way. Cog swapping Elsewhere we've considered what alternative standard production ratios are available - but that still leaves you with the power-consuming and limited-ratio alternatives helical tooth type gears. Not desirable in a competition orientated car. The solution to this comes in the form of several types of straight-cut gear sets (teeth are cut at 90 degrees across the gear as opposed to the angled helical type).

Rocker gear - General compendium

Whether you’re building a solid road performer or fire-breathing monster, the main goal is to improve air/fuel flow into the engine. The more you can get in, the more power you can get out. Cheapest chunk of power improvement comes from sorting the asthmatic manifolding and exhaust by applying a stage one kit. Then what? Considering the ‘get more in to get more out’ theme, the main restriction - all else being equal - is the valves and their behavior. How big they are, how efficient they are and how long they’re open for determines how much gets in with each gulp each bore/piston makes. Modified cylinder heads are popularly next, although it has to be said that although a well modified cylinder head will improve performance, the gain against cost is nowhere near that given by the ‘stage one’ kit application. A good stage one kit’s improvement verses cost is around £12.50 per 1 hp, a decent modified head typically £30 per 1hp - dependent on application. Hmm.

Valve Guides - Materials and Useage

Material choices for guides are down to two distinct types - cast iron and bronze. Yes, cast iron. NOT steel as described in many adverts and by vendors. Never have been, never will be. These are as fitted to the various A-series cylinder heads as standard in all applications. Cast iron is used because it is a very dissimilar metal from any used in valve manufacture - important to eliminate galling that causes seizure of the valves in the guides - is softer, yet resilient enough to wear well. Bronze, on the other hand, is a very general description as there are a variety of 'bronzes' used by various folk. In days gone by, the bronze base type used was 'PB1' (also known as 'Navy Bronze') - a phosphor-bronze alloy that was very orange in colour, and very soft, used primarily in race engines. Unfortunately they wore out very quickly. Silicone-brass content bronze is probably the most popular now - often with a high aluminium or manganese content - is very yellow/gold in colour.

MSE6 - POST 1992 Unleaded Stag

Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation. Three-angle valve seats in head. Super-quality MG Metro valves modified to increase airflow. MSE6 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head Part No Applications: MSE6, TAM1059, TAM1061, TAM2069, 12G1963, 12G1015, ADU4905 Inlet Valves: 35.6mm(1.401") dia. Original equipment type P/No. TAM1059 Exhaust Valves: 29.2mm(1.150") dia. Original equipment type P/No. TAM1061 Exhaust seats: Latest type Beryllium-based for lead-free fuel P/No. TAM2069 Valve Guides: AE Hepolite cast iron P/No. 12G1963 Valve Springs: Nominal 140lb. Max actual valve lift 0.400" P/No. 12G1015 Stem Seals : Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905 Chamber Volume: Nominal 20cc Combustion chamber volume used to give slight static compression ratio increase over

MSE6 - POST 1992 Unleaded Stag

Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation. Three-angle valve seats in head. Super-quality MG Metro valves modified to increase airflow. MSE6 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head Part No Applications: MSE6, TAM1059, TAM1061, TAM2069, 12G1963, 12G1015, ADU4905 Inlet Valves: 35.6mm(1.401") dia. Original equipment type P/No. TAM1059 Exhaust Valves: 29.2mm(1.150") dia. Original equipment type P/No. TAM1061 Exhaust seats: Latest type Beryllium-based for lead-free fuel P/No. TAM2069 Valve Guides: AE Hepolite cast iron P/No. 12G1963 Valve Springs: Nominal 140lb. Max actual valve lift 0.400" P/No. 12G1015 Stem Seals : Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905 Chamber Volume: Nominal 20cc Combustion chamber volume used to give slight static compression ratio increase over

MSE4 - Post 1992

Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation. MSE4 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head Part No Applications: MSE4, C-AEG544, C-AEG106, TAM2069, C-AJJ4037, C-AEA526, ADU4905 Inlet Valves: 35.6mm(1.401") dia. Tuftrided EN214N s/steel P/No. C-AEG544 Exhaust Valves: 29.5mm(1.161") dia. Tuftrided EN214N s/steel P/No. C-AEG106 Exhaust seats: Latest type Beryllium-based for lead-free fuel P/No. TAM2069 Valve Guides: Magnesium bronze P/No. C-AEA526 Valve Springs: Nominal 180lb. Max actually valve lift 0.500" P/No. C-AJJ4037 Stem Seals: Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905 Chamber Volume: Nominal 20cc Three-angle valve seats in head. Cooper S size valves with current maximum flow profiles and Tuftrided for durability/longevity when used with unleaded fuel (hence 'black' finish).

MSE4 - Post 1992

Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation. MSE4 - POST 1992 unleaded stage 2 (Road Rocket) large-bore head Part No Applications: MSE4, C-AEG544, C-AEG106, TAM2069, C-AJJ4037, C-AEA526, ADU4905 Inlet Valves: 35.6mm(1.401") dia. Tuftrided EN214N s/steel P/No. C-AEG544 Exhaust Valves: 29.5mm(1.161") dia. Tuftrided EN214N s/steel P/No. C-AEG106 Exhaust seats: Latest type Beryllium-based for lead-free fuel P/No. TAM2069 Valve Guides: Magnesium bronze P/No. C-AEA526 Valve Springs: Nominal 180lb. Max actually valve lift 0.500" P/No. C-AJJ4037 Stem Seals: Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905 Chamber Volume: Nominal 20cc Three-angle valve seats in head. Cooper S size valves with current maximum flow profiles and Tuftrided for durability/longevity when used with unleaded fuel (hence 'black' finish).

MSE3 -Pre 1992

Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively re-worked. Stone-ground finish in ports promotes ultimate fuel atomisation. MSE3 - PRE 1992 unleaded Stage 2 (Road Rocket) large-bore head Part No Applications: MSE3, C-AEG544, C-AEG106, TAM2069, C-AJJ4037, C-AEA526, ADU4905 Inlet Valves 35.6mm(1.401") dia. Tuftrided EN214N s/steel P/No. C-AEG544 Exhaust Valves 29.5mm(1.161") dia. Tuftrided EN214N s/steel P/No. C-AEG106 Exhaust seats Latest type Beryllium-based for lead-free fuel P/No. TAM2069 Valve Guides Magnesium bronze P/No. C-AJJ4037 Valve Springs Nominal 180lb. Max actually valve lift 0.500" P/No. C-AEA526 Stem Seals Latest 'top-hat' design with tensioner springs (inlets) P/No. ADU4905 Chamber Volume Nominal 20cc

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.

Thread Locking Compounds - Application

This is the frequently abused and mis-used stuff dolloped on to bolts/nuts to stop them coming undone. Having seen and heard of many horror stories concerning this stuff, I thought a few words of caution and common sense wouldn't go amiss.

There is a plethora of types on the market with no easy reference as to which to use for what application except in certain cases. Loctite have a very useful guide, their dealers generally able to help with choosing which is best for any given application. The trouble comes when folk buy stuff unwittingly from their local 'do it all' motorist/car spares place. Good stuff is expensive, and it doesn't go all that far. But at least it does its job when used in the correct applications. Unfortunately many buy a cheaper variety with not quite the same application strength, and then apply twice as much hoping it will do the job. It doesn't.

Thread Locking Compounds - Application

This is the frequently abused and mis-used stuff dolloped on to bolts/nuts to stop them coming undone. Having seen and heard of many horror stories concerning this stuff, I thought a few words of caution and common sense wouldn't go amiss.

There is a plethora of types on the market with no easy reference as to which to use for what application except in certain cases. Loctite have a very useful guide, their dealers generally able to help with choosing which is best for any given application. The trouble comes when folk buy stuff unwittingly from their local 'do it all' motorist/car spares place. Good stuff is expensive, and it doesn't go all that far. But at least it does its job when used in the correct applications. Unfortunately many buy a cheaper variety with not quite the same application strength, and then apply twice as much hoping it will do the job. It doesn't.

GEARBOX - standard production gearbox types

The first Minis rolled off the production line with a three-syncro gearbox, first gear as explained earlier was still a hit and miss affair.

Terminology -
FD - Final Drive

NOTE; A 'high' or 'low' ratio gear is in reference to it's performance, not it's numerical number. To illustrate - a 'high' FD ratio will give 'higher road speed', but will have a numerically low figure. A 'low' FD ratio will give lower road speed, but have a numerically high figure. A by-product of this will be reduced acceleration capability on the 'high' ratio, increased acceleration capability on the 'low' ratio. The main gearbox gears work in the exact same way.

I’m sure we’re all aware of Sir Alec Issigonis’ brilliant solution to the gearbox location in the Mini - just fold it up underneath the engine, simple. Following is a résumé of the production gearboxes to date.

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

GEARBOX - How they work

Having decided on or even implemented a course of action to bolster the performance of your Mini’s engine, maximising it’s potential should encompass a good look at the gearbox.