Whether you drive a modern or older car, it is possible to improve engine power efficiency by fitting selected performance products which simply bolt on to the engine externals. High flow air filters allow the engine to breathe better which, coupled with adjustments to the carburation or injection, will provide an improvement in power and response. Most factory fitted ignition leads are carbon cored and these will deteriorate with age. Fitting a high specification lead set will restore engine performance (especially under heavy engine load conditions), and will improve cold start operation. While on the subject of ignition, if your car is an older model, fitting an electronic ignition kit will ensure peak performance -
The value of any improvement or performance upgrade will be determined by the 'health' or otherwise of the engine in question. The areas of improvement mentioned thus far are fairly modest but to venture much further along the road to high performance will be doomed to failure if your engine is not in a sound condition. Some bolt-
Last and probably one of the most popular bolt-
So let us now move on to the more serious aspect of engine modification. The next logical step is to modify the top end where, in most cases, substantial power gains can be achieved. Choosing the correct stage of cylinder head and matching this with the right camshaft is very important. Most modern engines are overhead cam (OHC) design and removing the head can be carried out with the engine 'in-
Finally any attention or modification to the bottom end will require a complete engine strip down. If the cylinders are to be rebored then an increase in engine capacity is always worth considering. Whilst on this subject, it should be recognised that one of the easiest routes to more power is to fit a larger capacity engine. Many cars have various engine options for any given model so moving up from a 1300cc to a 1600cc engine or a 1600cc to a 2 litre should give a very noticable increase in performance. This type of work should be carried out by professional engine builder but for the competent enthusiasts amongst you here is the following additional advice:
Firstly, what follows is not intended as a complete guide to performance engine preparation. It should be regarded only as a supplement to manufacturers workshop manuals and specialist publications on engine tuning and related subjects.
First decide on your objective -
For occasional use cars (usually a second vehicle) the above criteria apply but, since power gains are more important than some loss in low speed torque and flexibility, the stage of tune will generally be higher. Off road competition cars allow the most scope for the ultimate stage of tune but will, invariably, have certain restrictions depending on regulations/homologations.
Cost: 'If you can't afford to do the job properly please think again'. The worse thing anyone can do is shop around for the cheapest parts. That is not to say you shouldn't find a cost-
Facilities: you will need a clean, light garage or workshop together with a comprehensive tool kit which will also include the following specialist tools:
If you intend to set up cam timing you will also require a DTI gauge and magnetic stand together with a 360° protractor. A good workshop manual should also be to hand.
Engines can be built on a flat bench but the job is far easier when using a proper engine stand. These are relatively cheap to buy (see our tool section) or can be hired. As mentioned previously, cleanliness and degreasing the components is essential, as is a good supply of lint free cleaning cloth. Use compressed air (if available) and/or gallery brushes to clear oil galleries, etc., and assist in the removal of any residual dirt or debris. (Note: always wear goggles and gloves and keep nozzles pointing away from body.
This is a general guide to correct procedures and will apply, wholly or partly to all types of engine rebuild. However, before the engine rebuild can begin the engine needs to be stripped down, cleaned and examined, a procedure which many undertake with undue haste. During the strip down the following should be observed:
Once stripped all parts should be thoroughly cleaned and inspected with specific attention to any areas of bad wear or damage e.g.: -
Cleaning should include the removal of all oil gallery plugs to enable thorough cleansing with special brushes (see tool section). Many parts can be re-
We will now discuss what modifications can be carried out to increase engine performance and some of the pitfalls to watch out for. We shall assume that any remedial work to restore these components to their original specification has been carried out.
Cylinder Heads: Arguably the most complex and important engine component especially when it comes to modification work. If a road stage cam kit is being fitted it will usually involve fitting the heavy duty valve springs. Always refer to the manufacturers fitting guide and check the valve spring fitted length -
Bottom End: The two most important criteria for this area of strength and weight. For the more moderate stages of tune the standard parts can be used.
Cylinder Block: Most standard blocks are strong enough to withstand at least a 50% increase in power or more. Problems usually arise because machining has compromised their structural strength. The two main areas for this are the cylinder bores and the top face. Excessive machining of either of these willresult in piston ring blow-
Crankshaft and Con Rods: These will be ok for most stages of tune provided they are structurally sound. Crack testing is advisable for any serious tuning especially if the components are second-
Pistons: With the exception of turbo-
Flywheel: Apart from being a handy place to fit a clutch and starter ring gear, the flywheel's primary function is to smooth out the transmission of. power from the crankshaft and for this you require mass (weight). The problem here is that this weight acts as a resistance to, as well as a store for, the energy produced by the engine. Lightening the flywheel will improve the engine's throttle openings but not the actual power output. Unless the flywheel is abnormally heavy we do not recommend flywheel lightening for road stages of tune. The slight loss of low speed torque and flexibility resulting from the tuning modifications can be greatly exacerbated by a lightweight flywheel. However, for all serious tuning a lightweight flywheel is essential. Standard cast iron flywheels can be lightened but there is always a risk of them exploding if too much material is removed from critical areas. The rule here is not to be over-
Clutch: Original equipment clutches should cope with moderate power increases (15-
Once all these components have been sorted they should be balanced. This will provide for a smoother more reliable engine, especially at high revs, by eliminating any vibration caused by unequal balance.
Lubrication Systems: All production engines employ a wet sump system where the oil lies in a reservoir or sump below the crankshaft This system works fine for most applications but the following points should be observed. High pressure pumps (typically 25-
The following bullet points highlight important procedures during the re-
Most engine modifications should be followed up with a professional engine tune. Apart from emissions, the correct ignition timing and fuelling is paramount if you want the best return for all the expense and effort you have put in. Get these important settings wrong and you may loose more than just a bit of power. Over-
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