Beginners Guide – GeneralBeginners Guide – General Published: 21st Apr 2017 - 0 Comments - Be the first, contribute now!
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It’s easy to uprate a classic – wrongly! So before you get out the toolkit and credit card it’s best to stop and read our beginners’ guide to tuning and improving first
On a roll
Before carrying out any tuning it’s essential that the engine is fit enough to dish it out so have a compression test carried out first. A rolling road ‘dyno’ tune can release a lot of hidden power even on a stock engine by carefully selecting the right ignition timing and fuelling for that individual unit as tolerances varied considerably during the 1960s and 70s. This tweak may yield all the zip you demand yet also be completely standard at the same time.
This is where most folks start but you first need to decide how much extra power you want, where you want it and why.
Ever since the Mini came along, it was seen as the Right Thing to dump the standard air filter in favour of sexy chrome ‘pancake’ types. However, while they look and sound the part their effectiveness is in doubt over the stock item. Much better are today’s freerflowing foam or cotton types from the likes of K&N and Pipercross which really work plus if you want to keep the engine’s appearance standard, there’s also similar performance filter elements which fit in the standard air filter assembly and are equally effective.
Don’t always assume that a performance filter will give a lot more power compared to a new or clean standard air filter. Also, the key to more power is to try to direct cold, dense air into the filter assembly
This is one of the easiest upgrades and the basic aim is to get more fuel into the engine more effectively. Depending upon car, there’s a choice of single, twin or triple carbs so long as you can obtain the appropriate inlet manifold. The ultimate is to have one carb for each inlet port but that’s impractical on the majority of engines so twin carbs is the pragmatic alternative, such as SU or Strombergs. However, a single twin choke carb is as effective and easier to keep in tune (as multiple carbs require careful balancing so they work in unison). Webcon recently specifically developed the Weber 32/36 DGV twin choke in conjunction with the Sunbeam Owners’ Club for the Alpine, for example. You need the right carb because too large or too extreme only wastes power and economy.
Fuel injection systems – either mechanical or electronic – have the edge over carburettors and can withstand moderate power increases from elsewhere without the need for altering with larger injectors, pump pressure, etc. However, it’s a specialist job to uprate. There are retro conversion kits which, along with a special ECU ‘brain’ to combine it to the ignition system, can transform old school engines in terms of performance and drive-ability. But it comes at a cost – say £2500 upwards.
Fitting a standard but larger carburettor from a sportier or biggerengined version of your classic can give a useful power increase plus retain standard looks and air filter assemblies
The camshaft is effectively the ‘brain’ of the engine, co-ordinating the opening and closing of the cylinder head’s valves to let fuel in and spent gasses out. A sportier performance camshaft will give more power but invariably at the expense of easy low speed pulling torque (as in the case of the MGB), especially ‘fast road’ types which means you’ll need to use the gearbox more to make the most of the newfound power. Also, while it’s one of the less expensive go-faster components around, the camshaft is only worth considering after you have uprated the carb and perhaps the cylinder head or the engine can perform worse than standard.
Fitting a camshaft from a sportier version of your car, such as a GT, is the best first step as they are usually only a mild upgrade but must be done in conjunction with new valve clearance settings and possibly the distributor and timing marks
These can be the unsung heroes of engine efficiency but their role is just as important, chiefly aiding the fuel/air mixture in and exhaust gasses out. Invariably, these look quite crude components. There’s not a great deal you can do to the inlet manifold to improve matters apart from removing any poor casting; tidy it up but don’t polish the ports as a rough surface aids fuel/air atomisation. Exhaust manifolds are another matter and for most engines there’s a sports manifold and exhaust system. Apart from expelling the gasses, a good exhaust also helps ‘pull’ in the new mixture by way of scavenging. On many classics, an enhanced manifold and system gives a good 10 per cent power gain on its own.
A GT or sports alternative from your model range (ie Mexico on an Escort, Cooper for a Mini) is the best starting point especially if you keep the engine in stock elsewhere as too wild a system will effect the fuelling and impair performance rather than improve it
A hotter head is the way to get ahead as this is where the combustion process takes place and most oldies suffer from poor designs and finishing, areas which were only really improved in the 1980s. Most classics are best tuned in this manner and there’s no shortage of choice for the popular classics.
Essentially, a tuned cylinder head will sport improved gas-flow characteristics to speed the process as well as make the burn more efficient plus feature hardened valve seats so unleaded fuel can be safely used without additives.
Generally, there’s three states of tune ranging from a simple clean up and re-profiling of the standard machining and perhaps a higher compression ratio (the valve sizes remain standard) to a full on re-engineering of the head sporting the largest valve sizes and compression ratio possible; this is mainly for competition work. Mid-way ‘Stage 2’ is perhaps the best compromise for most owners as it will improve power right across the rev range.
Armed with basic power drill attachments you can carry out a ‘super decoke’ on your own head, if in good order, by simply removing rough castings and smoothing away high spots, carefully lapping in the valves (for gas-tight seals) and using new springs. While not as effective as a proper modified head, fitting one taken from a larger engine (ie: a 1275 head on a 1-litre A-Series or a 1600 head on a 1300 cross-flow Ford) can yield a small but welcome power increase, especially if you also employ the inlet manifold and carburettor to suit
It’s not so much how much power you can gain here but to reduce how much you may be losing due to deterioration in the system. Replace old ignition leads with performance types and ensure you have the optimum spark plug grade and gap.
Electronic ignition is a worthy fitment even if you’re not after extra power as it ensures it can’t go out of tune, although for improved power you should look at a sports distributor at the same time.
Wear in the distributor is very common leading to ‘timing scatter’ so if in doubt have it overhauled. Setting the ignition with a dwell meter is better than feeler gauges while a rolling road tune can set the timing, under driving loads, exactly for your engine
Get the basics right first
Before any modifying to the running gear is contemplated you have to ensure that your car is in A1 condition beforehand as you’ll be wasting your time and money otherwise. Ok, you were going to replace the dampers anyway, but what about the king pins, suspension bushes and so on? And have the geometry set up by a marque expert – it can make all the difference too.
There’s more to having a faster car than tuning the engine; improving a car’s cornering speeds and braking prowess is as important as straight line velocities.
Most classics can be usefully updated in this department if for no other reason that age and mileage will have caused gradual deterioration that can go unnoticed. The first upgrade on most oldies comprises of uprated dampers, preferably adjustable types so their hardness can be tailored to suit. Note: Aftermarket replacements are not usually exactly to the original spec due to their universal fit nature. Telescopic dampers are superior to earlier lever arm designs and for several classics conversion kits are available.
Aftermarket dampers can be appreciably stiffer by design to account for ‘relaxing’ of the chassis due to ageing. Lever arm dampers can be reconditioned and are cheaper than new ones but budget ones invariably don’t last very long
This is the primary suspension with the dampers controlling the spring action. Harder springs are readily available to improve the handling and can reduce roll but make the ride harsher. A harder setting at the rear can also reduce understeer if it is excessive due to the roll stiffness but you ideally must combine any spring change with new appropriate dampers as there will be a mis-match. Lowering the car also reduces roll by lowering centre of gravity but spoils originality and usually impairs ride – it’s folly to think that racing springs are ultimate for the road as well as they are mainly over firm.
Springs from an estate or commercial variant are normally harder and can be bought cheaply at autojumbles but you need to know what you are buying and always replace in matched pairs
Anti roll bars and bushes:
These do what they say on the tin and are there to add stiffness to the chassis and reduce roll. They are available for most classics in various thicknesses but you need to speak to a specialist on what’s best for you as they need to be matched to the rest of the mods as they promote understeer. Rear anti-roll bars are fitted to some faster model derivatives and can reduce understeer but can also make the car twitchy. Replacing standard bushes with ‘poly’ types is popular as they last longer as well as provide added tautness to the chassis, but do speak to a marque expert first as it’s easy to overdo it and make the car too harsh as a result.
Check to see whether a range of anti-roll bars were used by the carmaker concerned, catering for largerengined or GT variants are available
Disc to drums
Most people think that you have to convert classics with all drum brakes to front discs if you want better stopping power. Not so! Drum brakes can work perfectly well if they are maintained properly and are equipped with quality linings (uprated types are available). Unless you intend to drive hard constantly and fade may become a problem a drum brake is quite acceptable plus they also have a ‘servo effect’ easing pedal pressure.
Converting to discs usually means a servo has to be installed to reduce pedal pressure. Also yet often overlooked, is that fitting front discs to an all drum system can lead to a major brake imbalance that requires different rear wheel cylinders or even the appropriate master cylinder to be also fitted. Speak to a marque expert or Owners’ Club if in any doubt.
Harder linings are the obvious first step towards better brakes but do you need them? Unless you drive particularly hard or are experiencing poor performance or fade, installing harder linings can have a negative effect as they will not reach optimum working temperature. If anything, a mild upgrade to the likes of EBC Green Stuff linings may be all that is required.
Search the autojumbles for new old stock as some experts regard the original asbestos type of linings superior in performance and feel
Discs and callipers:
Disc brakes displaced drum designs chiefly because they dissipated heat better and so reducing the chance of fading better. If your car has disc brakes already fitted then, apart from harder brake pads, you also have the option of fitting larger discs, to give a larger brake pad area to work with along with beefier callipers that exert more force on the disc although this is usually only necessary after largescale power gains or track work. Aftermarket types have the option of normal or ventilated types, some featuring special drilled holes or grooves. Rear discs can also be fitted but, as around 65 per cent of braking is done at the front, it’s usually quite unnecessary.
Before laying out good money on aftermarket kits, check to see if a larger disc or calliper was also fitted to your car, either due to being a sportier version or having larger engines in the range
In the right gear
Most classics are too low geared for today’s roads and why fitting modern five-speed gearboxes has become so popular that it’s now an accepted mod. However, while the extra ratio aids cruising, it has to be tailored to the engine’s power, which if too low will be counter productive as the car will never be able to ‘pull’ the higher gear. For example, Morris Minors are popular converts but it only works properly if the engine has been tuned to say around 70bhp+. If you wish to keep the car standard consider raising the gearing by fitting larger tyres or a higher axle ratio instead. Also, unless you are tuning the engine with a wider ‘rev band’, don’t think that a closer ratio gearbox taken from a GT version of your classic will help on its own – it usually can make matters worse!
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