Pistons - favourable features for maximum performance

The over-riding factor that influences just what is best for an A-Series engine is the block's propensity for flex at higher rpm, and the crank's equal propensity for flex at the same sort of rpm levels. Both combine to require a piston that is as stable as possible to maintain effective and consistent ring-seal performance. Reduced ring seal equals dramatically reduced performance. And none of this is at all helped by the relatively enormous distance from the wrist pin centre to crown height on most A-series pistons. Overall shape For the longest time, pistons were made round (well, 'ish' anyway) and straight sided (again - 'ish' is applicable here too) to form a cylinder, the top closed in to retain the all-important fuel/mixture charge; mainly because this was the simplest shape that would fill/block off the cylinder (bore) in an engine to greatest effect for minimum outlay.

Pistons - Mega piston performance report

Under 'Pistons - Favourable features for maximum performance' it would seem that the Mega pistons fit the bill just about spot on for all but perhaps the most extreme of racing engines. Or are they? Having used these pistons in all sizes from +0.020" to 73.5mm in all aspects of use - road/street to full race I am now in a position to give a report on their performance. Some have reservations about using the pistons in racing engines because they are a few grams heavier than other pistons available, and they are cast as opposed to forged. However, Mini Spares recruited the AE Hepolite Group for their unquestionable and renowned design and manufacturing expertise. The goal was to produce the most robust piston possible given reasonable cost and weight limits. Applying current technological advances incorporating their very latest hi-spec AE109TF lightweight alloy and special double heat treatments, the result is an extremely durable piston that will withstand greater cylinder pressure

Pistons - Whys and wherefores

For many, trying to make an informed decision about which type of pistons they should use for their application is a very difficult thing to do. Mostly you have to rely on guidance from a very few sources such as engine builders  and Mini spares specialists, who are most likely to recommend whatever it is they use or sell.
And that is not necessarily a bad thing where those companies have strong reputations for good quality products. But even those specialists may not know all that much about the pistons they use or sell. Particularly since trying to get any really useful information out of the manufacturers concerned is practically impossible. Try contacting AE Hepolite technical. Getting hold of someone takes real perseverance. Having achieved that meagre goal, enquiring about piston specification gets those ‘lemon sucking’ sorts of noises – anybody would think you are asking for the Holy Grail! So I’m going to try and cut through the techno-babble to help you identify a

C-STR313 Evolution 73.0mm pistons

The design concept for this new range of pistons from Mini Spares raised a few eye-brows at their introduction almost a year ago now

However, the design was arrived at after consultation with a couple of very learned and experienced A-series engine specialists and the piston manufacturers concerned – themselves a highly rated company that produces extremely hi-tech pistons for all manner of piston-driven engines including the mad, seriously engine-punishing world of 'drifting' cars tuned to run at extreme rpm producing extreme levels of BHP for protracted periods. Certain features of the piston and ring pack from pistons designed for these 'drifting' car engines were employed, receiving most attention of those used to more familiar, old school spec designs. Most completely over-looked the quality and material/heat treatment spec of the piston itself. A very durable, very high silicone content material heat treated to a specific requirement ensures tough, reliable and lo

P20950 998 flat top pistons – Review by K Calver

The end of the 2007 racing season is in its last throes. I have had several 998-based race engines returned for their post season post-mortem, and I have very good news to report.
The most arduous scenario the 998 engine could possibly see is that of the Class One Grass Track racing fraternity.

Over-boring blocks for 73.0, 73.5 or 74mm diameter pistons by K Calver

I frequently hear the phrase "big-bore engines tend to be unreliable long-term because of head gasket problems". Which is complete rubbish, even when non-Payen head gaskets are used.

These big-bore engines can be supremely reliable - providing the are machined and built correctly in the first place. Something that continually astonishes me doesn't happen even when engines are built by some of the self-proclaimed A-series 'experts'.

SHOCK ABSORBERS

Technical lowdown on shock absorbers,what to look for and what to buy Having introduced the fairly unknown Kayaba (KYB) range to the mini market in 1997 I am still amazed how gullible people are when buying cheap dampers. I have tried every type popular type available in the last 35 years, Armstrong including their adjustables, Girling, lockheed, Koni, Spax., Avo, Bilstein,Monroe,Boge,Gabriel and GMax The best to date were probably the very expensive special design Koni adjustables that we had built for the Monte Carlo rally. I also used the spare set on my 8 port car. You get what you pay for? For a non adjustable, Bilsteins rate highly although like the Koni specials are expensive, but you get what you pay for. The essence of a quality damper is to upgrade performance by using more sophisticated higher quality component build in the valving, piston, rod and seals etc along with a performance upgrade to improve the cars road holding.

CAM TIMING - Conventional method using DTI, etc...

Equipment required - one 0.500” minimum capacity DTI with magnetic stand, 360-degree protractor and a piece of reasonably thick gauge wire to use as a pointer. Terminology - DTI - Dial Test Indicator/dial gauge Protractor - degree wheel 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. Rotate crank so piston one is at the bore top (TDC). Fit timing gears 'dot-to-dot'. Set up DTI with stem resting on number one piston centre with a little preload. Rotate crank backwards slightly (anti-clockwise looking at the front), then gently forwards observing the DTI, watching where the needle stops before descending. This is TDC. Repeat this procedure, stopping when the needle reaches its zenith. Zero the dial scale, and repeat until satisfied the needle shows zero on the scale.

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.

CAM TIMING - Basic Notes

To avoid lots of swearing and unnecessary damage, check the timing gears slide neatly onto their respective bosses. If tight, first check for any high spots in the gear bores and key-way slots. Clean out using with fine emery cloth, medium Wet 'n' Dry paper, or some such. Remove the Woodruff keys then dress the bosses using abrasive material as mentioned previously. Re-check fitment before re-fitting keys. Check the key-ways and keys too before re-fitting. Get rid of unwanted sticky-out bits on the keys that would inhibit a slide fit. Clean out the key-way and de-burr top edges. I always file a slight 'flat' across them to give plenty of clearance to the gear key slot. If the pulley is a slack fit on the key, turn it anticlockwise before nipping the bolt up. ALWAYS fit it like this. It's imperative to fit cam (and followers in the case of solid wall blocks) following manufacturers instructions precisely using a good quality cam lube.

Camshaft Design

Elgin Cams is a company that is a direct descendent of such famous California specialists as Isky, Delong, Winfield, etc. etc. Elgin has taken the art of cams into the science of the '90's. Computer designed and handcrafted workmanship guarantee a first class camshaft. Custom designed cams are a specialty. Part No Applications: CAM001, CAM002, CAM003, CAM004, CAM005, CAM006, CAM007 Elgin has made cams or sold his design to General Motors, Ford Motor Co., Nissan Corp., Zakespped International, Porsche Motor Sports, Winston Cup "Engine Builders. Elgin has the largest percentage of cams used at the SCCA Runoffs from GT-1 to Formula-V. He also has provided original or new technology for antique and vintage racers. Much information has been recorded about the four stroke internal combustion engine and yet only a small percentage of people really understand how it works and fewer people know how to modify an engine to suit their needs.

DIAPHRAGM SPRING - Verto types including injection

The Verto/Valeo type diaphragm included the pressure plate in its assembly, much like a 'normal' car set-up. The spring being of the 'finger' type as opposed to the disc spring used on earlier, three-piece assemblies. There were originally three diaphragm specifications using progressively stronger springs - small-bore, big-bore, and Metro Turbo. Later joined by the type used on the injection cars, though most definitely not interchangeable. Initially, the biggest problem was the Turbo ones were never really available on their own. If you wanted one you had to buy a whole clutch/flywheel assembly - the cost exorbitant. Rover originally believed that if the clutch plate was worn out, then the flywheel and pressure plate would be too. It has only been recent times that the diaphragm/pressure plate has been available on it’s own - but not until after the Turbo unit became unavailable. Even that has changed recently with the cessation of the Turbo diaphragm as a service part.

DIAPHRAGM SPRING - Verto types including injection

The Verto/Valeo type diaphragm included the pressure plate in its assembly, much like a 'normal' car set-up. The spring being of the 'finger' type as opposed to the disc spring used on earlier, three-piece assemblies. There were originally three diaphragm specifications using progressively stronger springs - small-bore, big-bore, and Metro Turbo. Later joined by the type used on the injection cars, though most definitely not interchangeable. Initially, the biggest problem was the Turbo ones were never really available on their own. If you wanted one you had to buy a whole clutch/flywheel assembly - the cost exorbitant. Rover originally believed that if the clutch plate was worn out, then the flywheel and pressure plate would be too. It has only been recent times that the diaphragm/pressure plate has been available on it’s own - but not until after the Turbo unit became unavailable. Even that has changed recently with the cessation of the Turbo diaphragm as a service part.

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 - 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

Brakes - Rear brake bias adjustment

When altering the front brake set-up away from the standard installation, it invariably alters the amount of rear brake bias needed to re-balance the cars brake balance.

The problems start occurring when folk graft alternative brake set-ups onto the front of their Minis. Be this 7.5" discs onto a previously drum-braked model, or going from current standard disc set-ups to one of the 4-pot varieties. The question then is 'what bore size rear wheel-cylinders do I need?' Unfortunately this isn't straightforward. Actually, that's not strictly true - more on this later. The pressure developed in the lines determines brake effectiveness - aside from disc size, pad type, co-efficient of friction, etc. that is. Understanding this may assist in choosing which way you should go for your particular set-up.

The basic facts you need to remember when dealing with brake pressures is how they are affected by the components you use.

Brakes - Split brake systems and adjustable bias valves

You can only use the MS72 adjustable brake regulator/bias valve with a front/rear split system. Definitely NOT the diagonal split type (for identification see 'Brakes - Rear brake bias adjustment'). These should have been 'X-ed' at birth. Makes the car handle very interestingly when the system only operates the diagonally opposed brakes. Scary stuff. Almost as much fun as when the rears only work on a front/rear split set-up - particularly as the PDWA is built into the master cylinder, and it still has to go through the FAM7821 pressure regulator valve! Damn near no braking on the rear. Either way - split system brakes are grossly inefficient when only using half the system as they are designed to do when a failure in the other half occurs. Quite frightening. To install the MS72 into a front/rear split system, it needs fitting into the rear feed line. Determining which this is can prove difficult if the system has already been tampered with or new replacement components fitted. Nam

Cylinder head - What can easily be achieved

During a discourse with the editorial staff at Mini Mag, it was decided the build feature presented an ideal opportunity to demonstrate just exactly what such an engine build is capable of in days where it's generally believed you have to have an all-singing, all-dancing 1380cc engine to have an enjoyable road burner - leaving those with very limited budgets a little depressed. During a discourse with the editorial staff at Mini Mag, it was decided the build feature presented an ideal opportunity to demonstrate just exactly what such an engine build is capable of in days where it's generally believed you have to have an all-singing, all-dancing 1380cc engine to have an enjoyable road burner - leaving those with very limited budgets a little depressed. So the idea was to finish the engine off using a relatively 'mild' specification to maximise drivability. The camshaft used was the fantastically versatile Swiftune Racing SW5 profile that provides drive from nowhere up to 7,000rpm - d

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.

Cylinder heads - About Min Tec Heads

'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. Terminology - VFM - Value For Money CR - Compression Ratio VE - Volumetric Efficiency 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). Combustion chamber volume used to give slight static compression ratio increase over standard. Head mods employed greatly increase volumetric efficiency, boosting actual running (dynamic) compression ratio. Where much sportier cam profiles are used, a higher compression ratio is advised to achieve maximum power potential. Seek advice on what is required'. That is the opening paragraph from the fitting instructions sheet as supplied with the heads I do for Mini Spares.