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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.

Previous rocker spacer kits offered by various A-series specialists have largely contained just three spacers in various forms and materials. They all had one thing in common though – they were inadequate. The issues revolve around two basic problems – the varied position of rocker post and head studs through factory machining tolerance and the variety of widths of rockers arms.

C-AEG645 OFFSET ROCKER POST SET

Combined with the C-AEG644 offset rocker bush set, a further 0.030” valve lift may be attained.

It is not advisable to use just the posts on their own, as the rocker pad may fall off the valve stem at full lift. This will almost certainly occur with the latest sintered type rockers. These rockers are identifiable by their very angular shape and •'5f”AF lock nut.

CAM TIMING - Mechanical Method

CAM TIMING - Mechanical Method Part No Applications: MD256, MD266, MD276, MD286, MD286SP, MD296, MD296SP, MD310SP, MD530, MDM266/KIT, MDM276KIT, MDM286KIT Equipment required - Stop plate - mechanical stop plate for setting TDC (see text). Set of feeler blades Terminology - TDC - Top Dead Centre, when piston is at highest point in bore BTDC - Before Top Dead Centre, before piston reaches highest point in bore ATDC - After Top Dead Centre, after piston has reached highest point in bore Accurate piston position indication is the first goal. You need to know exactly when piston one is at TDC. Without engineering measuring equipment a ‘stop plate’ is required. This you will either have to manufacture personally, or get one made. You need a piece of metal plate long enough to span the bore plus a couple of the head stud holes on either side - about 4.750" long by 1.375" wide will do the trick.

Camshafts - Scatter cams, pros and cons

To scatter or not to scatter, that is the question. This whole 'scattering' deal has befuddled many. The only real prose produced on the subject, and 'advice' handed out by many so-called 'specialists' tends to be somewhat tainted with large chunks of mysticism - inferring there's some kind of black art involved. The simple fact is the principle is very basic and easy; it's getting a cam with the right profile and figures applied to it that will actually work as a scatter profile that's the hard part. And this article does not mean I am all for scatter pattern cams. I will illuminate… We are all pretty much aware that the A-series is a real oddity, largely because of the siamese (shared) port work - cylinders 1 & 2 share an inlet port, cylinders 3 & 4 share an inlet port, and cylinders 2 & 3 share an exhaust port. Very weird compared to the more familiar head designs found on almost every other engine type that has one inlet and one exhaust port per cylinder.

Cylinder Head - Unleaded Fuel Use

The specter of 'unleaded fuel only' - instigated in UK on January 1st 1999 and seemingly from decades ago across the rest of the world - seems to be forcing more and more folk into frightened, panic orientated action. And Mini owners are featuring heavily in this. See bottom for useful part numbers. The situation not at all being helped by all sorts of conflicting information from 'leaned' sources, such as lead levels in humans has declined greatly since 1935 - despite the rapidly expanding ownership of petrol-burning vehicles. And benzene and toluene used in unleaded fuels are cancerous. Still, the powers that be are relentlessly forcing through the 'no heavy metals in fuel' bills, not being at all put off by such trivia. Not surprising bearing in mind the complete debacle on the catalytic converter front - the type decided on for world wide and universal use was developed and tested in California!

Cylinder Head - Unleaded Fuel Use

This valve spring set has been developed to fit standard sized top caps, and cope with racing rpm, savage cam lobe opening rates and high valve lifts up to 0.520”. Most cylinder heads when modified for racing culminate in a fitted valve spring height of around 1.420” to 1.440”.

C-AEA527 DUAL VALVE SPRINGS FITTING INSTRUCTIONS

See bottom for useful part numbers.

However where possible, it is always advantageous to correct and match the valve spring heights (measured from the spring seat in the head to the underside of the spring retainer cap), as these will vary particularly where new valve seats are cut and the standard valve spring seats are left – some by as much as 0.050”!

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

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 - Identification Data Updated

If you have the engine tag still attached to the engine - just in front/below the thermostat housing - or perhaps the original engine number in the log book then the following should help you determine which engine you have. For Metro units, see 'Engine - Metro identification data'. Original engine identification numbers 850cc 8A Austin up to 25000 8MB Morris up to 25000 8AM Austin & Morris 25000 onwards 8AH Austin & Morris Automatic 8AJ Austin & Morris closed circuit breathing 8AK Austin & Morris automatic with closed circuit breathing 8WR Wolseley Hornet & Riley Elf 8AC Moke 85H/101 All variants 1969 onwards Note: third suffix letter denotes compression type, L = Low, H = High, e.g. 8AM/U/H101 denotes high compression. 998cc 9WR Wolseley Hornet & Riley Elf Mk2, pre closed circuit breathing 9AD Austin, Wolseley Hornet & Riley Elf Mk2 with remote type gearbox and closed

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.

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.

Valves, guides and springs.

Concerned about fitting up-rating parts to injection engines? A short while ago I had several conversations via e-mail with folk abroad who were a little concerned about fitting up-rating parts to their injection engines - like one of the many 'GSi' tuning kits available. A rumour had been put about that fitting this kit caused engine damage. Closer questioning culminated in the rumour saying that the high lift (1.5 ratio) rockers were causing camshaft and valve/guide damage. You know me - I can't let things like this alone until I find out the root cause. After some more digging and goading, I believe I've found the problem.

Cam damage is usually caused by something amiss in the valve train - obviously. Since the engines concerned were as they came from Rover and had done many thousands of miles without issue, it had to be something to do with these kits.

Valves, guides and springs.

A+ head castings - despite having the same 12G940 casting number - are considerably different in appearance, loosing the flat area behind the thermostat housing and around the rest of the rocker/head stud areas to a sculptured look - where these areas are replaced by a 'sunken' cast finish. The A+ castings were introduced with the appearance of the Metro in 1980, although some late 1275GTs (1979-on) had them fitted. Generally they are easily recognised by their colour - a putrid yellow on the small-bore castings and bright red on the large-bore ones, a paint finish that is VERY difficult to remove, even in a chemical tank. The MG

See bottom for useful part numbers.

Cylinder head - Suitability basics

Whatever else owners do to their Minis by way of interior/exterior modifications or none at all, a very large proportion desire and search for an increase in engine performance.

See bottom for useful part numbers.

Now this may not be super-sonic speed-inducing power, it could just as well be for maximum economy. In either case, it's the engines volumetric efficiency (VE) under scrutiny - it's ability to breath in as much correctly proportioned air/fuel mix as possible in any given situation. Although the induction/exhaust system plays an important part, there are effectively two major factors that dictate performance increases - the camshaft and cylinder head. The induction and exhaust elements (stage one kits, exhaust systems, etc.) and camshafts are covered in various other articles in my 'Corner'. So here we'll have a look at cylinder heads and dispel some of the myths and legends surrounding them.

Articles search results for rockers

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