Primary Gear - Bush Replacement

With the cost of new primary gears spiralling ever upwards, and the availability of good, serviceable used ones, fitting new bushes to existing gears is becoming a more common solution. For some reasons for bush failures and rectification to stop it re-occurring, see article Primary gear - Bush problems. Since there is no useful information given in any of the workshop or DIY manuals on this subject, following is my approach to dealing with the issue. The first thing to get to grips with is which bush is which. This has added an element of confusion to many conversations I have had with folks on this subject, so - the FRONT bush is the one nearest the engine block, the REAR bush is the top-hat one nearest the flywheel. This is because the front of the engine is actually the radiator end - quoted in 'in-line' engine-speak. The REAR bush is the same on all primary gears - be they for small or large bore engines. The FRONT bush is different for each though; the small-bore one is smaller

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

Primary Gear – Bush Problems

Although not of immediate interest to many road-runners/street-burners, mainly accorded to the racing scene, it seems to be a perplexing problem to a very large number of folk around the world, and has burned up plenty of telephone time.

part numbers: 13H2934, LUF10005, CE12, 22G109, DAM8889, DAM8887

With the cost of new primary gears spiralling ever upwards, and the availability of good, serviceable used ones, fitting new bushes to existing gears is becoming a more common solution. For some reasons for bush failures and rectification to stop it re-occurring, see article 'Primary gear - Bush problems'. Since there is no useful information given in any of the workshop or DIY manuals on this subject, following is my approach to dealing with the issue.

The first thing to get to grips with is which bush ...

Brakes - How They Work

This time we’re going to look at just how brakes do what they do, and ways to improve them. Without a doubt the most important point to get sorted at the outset is just what makes brakes do their thing - FRICTION. The sole purpose of the brake set-up on any vehicle .....

Brakes - Fitting Discs and Required Ancillaries

What you actually need for the disc/drum conversion is pretty straightforward. Disconnect the steering arms, top and bottom swivel-pins, CV joint, and flexible brake pipes at the subframe - that’s it. There are, however, a number of ancillaries to consider.

Basics

Basics Fitting discs designed for the Mini is easy enough. Just make sure you use CV gaiters for the disc-brake set-up - these have a different bellows shape to stop the gaiter rubbing the inside of the hub. The drum type will rub, then split, shedding grease all over the place. Moly grease is mighty mucky stuff to deal with and doesn't assist braking at all! A tip for racers - to stop the gaiters over-expanding when getting very hot and imitating the aforementioned, put either a decent sized split pin or (my favorite) a piece of very small bore pipe - as in the type supplied with WD40 aerosols, etc. - under the retaining strap on the drive shaft. This allows air to escape and return,

Brakes - Fundamental Considerations

When looking to increase their cars performance, most folks immediately turn to considering higher engine power outputs. Because of this pre-occupation brakes tend to slide down the improvements priority list. However, they are far more important - being able to accelerate at warp speed to hyper-space in the twinkling of an eye is all very well, but disastrous if you can’t stop. You will make a very big hole in the scenery, and possibly end up wearing an wooden over-coat. Getting the braking system sorted out can help to make the car quicker, as you will be able to more confidently, therefore maximising speed in any given situation. Being one of those ‘sciences’ used in the automotive industry I hope to shed some light on the subject as it's another of those where many questions from confused and mislead folks that clog up my e-mail board. The advent of the Metro, and the brakes used on it has spawned a lot of activity in this direction. It was soon discovered that they could b

Engine - Running in Procedure

This is another of those subjects that crops up on the message board frequently. I am constantly surprised by the number of engine builders - or people who charge other folk for building engines at any rate - that never hand out such an information sheet. It seems pretty daft to me that having taken a wad of money off of a customer for an engine you've lovingly put together, you'd want to help that person get the very best out of the engine. And the running/breaking in procedure is absolutely crucial. It at least ensures no damage is incurred when the engine first bursts into life. A collection of the usual suspects have explained their own methods on the board, along with various others - many of which probably work just as well for them, a few which are down-right dubious. Following is a sheet I administer with every customer engine I build.

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.

Clutch - Adjustment of operating linkage

This is one of those areas where there is more than one way to skin the cat - depending on who you speak to. This is the method I have used for eternity, which has been totally reliable and never had a problem with.

This only applies to non-Verto type clutches, as the Verto types are not adjustable. You just have to make sure all the operating linkage components are in good order.

First off, ensure your operating linkage is up to scratch. For details on this, see 'Engine transplants - Clutch and flywheel'.

Satisfied all is OK, you can proceed with setting the linkage up.

1 - Remove/disconnect clutch return spring.

2 - Undo throw-out nuts (15/16"AF nuts on outer end of plunger) lock nut and back nuts off away from clutch cover.

Clutch plates - Pre-Verto types.

There are generally three types to be concerned with these days - standard pre Verto, fiber rally/race, and sintered race. All at 180mm diameter.

Standard-type plates. The pre Verto plate has a spring-steel centre section to which is riveted the lining. Between the linings are sprung washers. These take up some of the shock impact of engagement and slight surface imperfections of the flywheel and pressure plate surfaces. Providing a genuine Unipart/AP Lockheed one is used, it will cope with most fast road applications without any problems. This includes almost all road-going standard over-bores (+0.020” to +0.060”) and a vast majority of big-bores (1380/1400). That covers up to 110 bhp and/or 90lb ft. - both flywheel measurements of course!! It is the torque that causes more problems than out-right horsepower. It can also be used in the Verto set-up to improve judder/grip/slip problems experienced when using the 'correct' standard plate...

RUNNING IN NEW ENGINES

Install engine. It is absolutely imperative that the cooling system is more than sufficient to deal with any temperatures likely to be produced by the engine. More power means more heat to be dissipated. A standard radiator is very unlikely to be able to cope with a reasonable power increase over standard.

Do not fill cooling system yet. Set clutch throw-out and free-play take up. Double-check all connections electrical, oil, fuel and cooling system. Put in engine oil – use a cheap multi-grade mineral oil. DO NOT use either semi or full synthetic oils. They will stop the rings from bedding in. Remove spark plugs, and spin engine over in bursts of a few seconds to pick up oil pressure and prevent starter motor damage. DO NOT start engine until oil pressure picks up.

Once oil pressure is showing, check ignition timing statically. Set to figure advised by distributor maker, or if no figures available, set at around 6-8 degrees BTDC. Re-fit spark plugs a

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 - Clutch and flywheel assemblies

To go in to all the possible permutations would take a few chapters on it’s own. Suffice to say that the Metro had a few weirdo fitments such as cable operation, an in-line ‘damper’ (some got fitted to Minis too - eek),

Terminology -
BBU - Big Bore Units
SBU - Small Bore Units

NOTE: This information is largely concerned with transplanting a large-bore engine into a small-bore engined Mini. For further information on clutch and flywheel assemblies in particular, refer to relevant separate article.

To go in to all the possible permutations would take a few chapters on it’s own. Suffice to say that the Metro had a few weirdo fitments such as cable operation, an in-line ‘damper’ (some got fitted to Minis too - eek), and ‘top-hat’ plunger and rod bearing operation.

Engine transplants - Clutch and flywheel assemblies

To go in to all the possible permutations would take a few chapters on it’s own. Suffice to say that the Metro had a few weirdo fitments such as cable operation, an in-line ‘damper’ (some got fitted to Minis too - eek),

Terminology -
BBU - Big Bore Units
SBU - Small Bore Units

NOTE: This information is largely concerned with transplanting a large-bore engine into a small-bore engined Mini. For further information on clutch and flywheel assemblies in particular, refer to relevant separate article.

To go in to all the possible permutations would take a few chapters on it’s own. Suffice to say that the Metro had a few weirdo fitments such as cable operation, an in-line ‘damper’ (some got fitted to Minis too - eek), and ‘top-hat’ plunger and rod bearing operation.

Engine transplants - Engine to gearbox fitment

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

Terminology -
BBU - Big Bore Unit (1275cc based engines)
SBU - Small Bore Unit (850/998/1098cc based units)
FD - Final Drive

NOTE: This information is largely for transplanting large-bore engine units into small-bore engined Minis. For further information on up-grading transfer (drop) gears, refer to relevant separate article.

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

Engine transplants - Engine to gearbox fitment

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

Terminology -
BBU - Big Bore Unit (1275cc based engines)
SBU - Small Bore Unit (850/998/1098cc based units)
FD - Final Drive

NOTE: This information is largely for transplanting large-bore engine units into small-bore engined Minis. For further information on up-grading transfer (drop) gears, refer to relevant separate article.

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

Engine transplants - initial information and engine choices

Is this familiar? - You take the small one out; you put the big one in. In, out, in, out, shake your fist about, you do the hokey-cokey and you turn around, that’s what it’s all about...

Terminology -
BBU - Big Bore Unit
SBU - Small Bore Unit
Bodge - English term for 'make do' engineering- assured to fail at an in opportune
Moment.
Dizzy - Distributor

NOTE; this information is largely for transplanting large-bore units into small-bore engined cars.

Is this familiar? - You take the small one out; you put the big one in. In, out, in, out, shake your fist about, you do the hokey-cokey and you turn around, that’s what it’s all about...kinda sums up the situation many folk find themselves in when attempting to endow their beloved Min with a more impressive turn of speed.

Primary Gear - Bush problems

Although not of immediate interest to many road-runners/street-burners, mainly accorded to the racing scene, it seems to be a perplexing problem to a very large number of folk around the world, and has burned up plenty of telephone time. Distilling the myriad of 'the symptoms go like this' descriptions down from various languages it has been put to me in - the end result was always the same. The bushes at one end or other, and sometimes both, had failed in their duties. Incidentally - some of the confusion when trying to sort the problem descriptions was down to misunderstandings about which end of the primary gear is which. To put the record straight, the end nearest the engine is the FRONT end. Consequently the end nearest the flywheel is then the REAR end. The two biggest outstanding symptoms were severe oil leaks onto the flywheel/clutch assembly, and difficulty/impossibility in selecting gears.

Primary Gear - Setting end float

A fairly crucial part of how the primary gear operates is its tolerances and running clearances. 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.

Terminology: DTI - Dial Test Indicator Also, later factory assembled engine units (from about 1992 onwards) were built up using whatever 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 primary gear was no exception. Too much end float and clutch disengagement is adversely affected, the gear floating up and down the crankshaft in unison with the clutch plate. The result is a graunching gear change since the plate isn't clearing the flywheel and pressure plate surfaces fully. Too little end float and the gear is likely to be pinched tight as it

C-AEG423 - LIGHTWEIGHT STEEL OUTER FLYWHEEL SECTION, VERTO TYPE

Reduction of rotating mass releases more power to accelerate the car as the engine sees less weight to accelerate. Considering for a Mini that a mere 1lb reduction in the rotating mass of the flywheel causes a loss of accelerative weight to the tune of around 12lb - the benefits of rotating mass reduction are obvious. The C-AEG423 weighs some 4lbs less than the standard item.

To extend it's range of superior quality, light-weight steel flywheels, Mini Spares has produced this component to give the later model, SPi Mini owner the benefits from such weight saving. This component has the flywheel sensor reluctor ring machined into the flywheel itself. However, it is NOT compatible with the standard injection diaphragm/spring.