You are taking 1959 basic design and trying to get the sort of performance expected from a 1997 performance hot hatch
A 1275GT engine produces 56bhp as standard, my 1330 engine produces 95bhp, that extra power gets you there quicker, so you need to stop quicker, an extra 40bhp also generates a pile more heat as well as more wear!
Start tuning the b*****ks out of your car without due regard for what sort of Pandora's Box you are opening and your £££££££'s will end up in the scrapyard either through heat-death, metal fatigue or as a result of a fatal attraction to a brick wall or articulated lorry.
Oil Pressure: your existing oil pressure warning light comes on at 5psi, a slow oil leak could mean you sit on the M40 at 80mph for a half-hour running an engine at 6000 revs with 10psi of oil pressure without knowing. Rather than ruining a precious engine, purchase a high-pressure oil warning switch (Mocal make them) which comes on at 25psi, still low for running pressure (normally 50psi) but high enough to warn you of a problem before the engine is scrapped. FIT AN OIL PRESSURE GAUGE TOO, this will warn you of problems long before they are REAL PROBLEMS. They are easily fitted using adaptors allowing the existing warning light to be retained.
If you fit a mechanical oil pressure gauge (using a capillary) ensure the tube is routed (and fastened) away from hot bits (like manifolds) and sharp bits (like the holes you drilled to get the tube into the car).
Cooling (water): The latest minis have front mounted radiators with electric cooling fans (welcome to the 90's Mini!) if your car is one of the millions that haven't, your radiator is hiding from you, sitting up in the wheel arch, and it relies on the wind through the grille and the twee plastic fan to cool the car, standard 850's can boil sitting in standing traffic never mind a rad designed for 56bhp presented with 95!!!
If you want a practical solution to a cooling problem that isn't due to clogged waterways, incorrect timing, running lean, sticking thermostat or any other similar problem FIT A HIGH CAPACITY RADIATOR, these look and fit like ordinary rads but have a far greater cooling capacity than standard and can dissipate that excess heat without resorting to a major plumbing exercise..
Cooling (oil): The heat dissipated from the metal to the oil is normally lost into the water system and dealt with by the radiator, pump out more bhp and this method of cooling the oil is overstressed, the oil heats up (and breaks up), the oil pressure drops and when metal-to-metal contact occurs the lifespan of the engine can be measured with a good stopwatch.
Supplied with the necessary hoses, the cooler fits in front of the engine behind the grille, plumbing in in-place of the copper pipe running from the top of the block to the filter head. OVERCOOLED oil can be a problem if the moisture created by combustion and the petrol vapours cannot be "boiled off". The "mayonnaise" commonly seen on the oil filler caps of cars driven short distances( that never warm up) is typical of this build up of moisture (as well as being a possible sign of a leaking head gasket!).
Change The Oil: Doing oil changes at 3000 mile intervals is worth the £10.00 per time if you are using cheap oil (better than £400 for a new engine eh?), Use good quality oil and posh stuff like Mobil 1 for highly-tuned engines.
Change The Filter Design: When a mini engine is cold and the oil is thick, the oil pressure can be very high indeed, behind the big dome nut near the oil pipe is a pressure release valve to keep the maximum oil pressure below 60psi (ish), if this valve opens oil drops straight into the sump, in the filter head is another pressure release valve (to stop the filter exploding if it blocks up?) IF THIS VALVE OPENS UNFILTERED OIL GOES STRAIGHT INTO THE BEARINGS.
Fitting a remote filter head in line with the oil cooler (or instead of the oil pipe) will ensure a larger filtration area and at the same time ensure all oil going through the bearings gets filtered. The existing filter can be retained
or the filter head can be replaced with an adopter to plumb in the remote filter head.
The Brakes on your fire-breather were designed to stop the average driver on the way back from the shops not on the way round Castle Combe circuit, uprated performance needs uprated brakes. Start thinking about brake mods before engine mods as there are a finite number of pairs of soiled underwear you can carry in a MINI (your insurers will appreciate uprated brakes too)
The minimum you should have is 10" or 12" wheel front discs (ideally current 12" wheel mini front calipers if you have a drum braked 12" wheeled mini). When considering a change to your braking system, consult an expert, your life is in your hands here! Swapping brake cylinders and calipers can affect the balance of the system, make the wrong choice or use the wrong components and you can be spinning down the road at the first give-way line.
Start moving things around by raising or lowering your car (by cutting the ally trumpets or using Hi-Los) or fitting uprated tie rods etc, and the original geometry of the suspension (camber, castor, tracking etc) can change both for the worst or for the better.
Without reference to alignment equipment, you can
turn your pride-and-joy into a tyre eating monster or possibly turn it into
something that handles like a bag of S**T!
I improved COO's handling with
To be continued IF YOU NEED HELP.....MAIL ME