The intention of this document is to help a 308 GT4 owner get their car running well by giving a quick guide to information which is specific to this car and which might not be known by even the most experienced technician who does not have specific knowledge of this model. Most aspects of the car's maintenance are simple. This document does not intend to serve as a guide to maintenance or to techniques which are common to other cars.

fuse blocks
The standard fuse blocks are, at best, unreliable, at worst a fire hazard. They were used across a range of Ferraris of similar vintage and there exists that rare thing: universal agreement that they are of poor design and construction.
These fuse blocks are a major source of unreliability. They develop excessive resistance and subsequently overheat and melt. Several different styles of replacement are available:
"Birdman's" fuse blocks fix the original issues, make use of glass fuses and cannot accept fusebox covers.
"Sam Spuranoff's" fuse blocks are designed by a competent electrical engineer, thoroughly load tested, make use of blade fuses and accept the original fuse block covers. Only very close inspection reveals that they are not original. They may not be easy to get hold of.
"Turtle Farmer" makes another style of fusebox, also using blade fuses. It appears well made. This is a single fuse box which replaces the two original fuse boxes and so it is visibly not original although the appearance is neat. The fusebox features a labelled cover which covers the connections (although not the fuses themselves) and it also holds three spare fuses.
"classicretrofit" makes fuse boxes to order. They feature blade fuses and appear well made. They have a similar form to the original fuseboxes although they are visibly not original. They feature transparent plastic covers which do not have labels.
Choose according to requirements, budget and availability but any of these solutions are better than the original fuse boxes.

Carburettor jetting
Carb jetting is a slighly more controversial issue and there are as many inexpert opinions as there are poorly running cars. It is my experience that some degree of rejetting is absolutely necessary in order to get acceptable running characteristics. When new, jetting varied significantly in different markets and different years. Both F36 and F24 emulsion tubes were used and these give quite different characteristics.

The following are rules-of-thumb which are likely to apply to your car:
F36 gives a cleaner running car, less prone to richness and gives a more consistent mixture over a much wider rpm range.
Standard jetting tends to run excessively lean at high load and high RPM and a smaller air corrector jet is usually required.
Main jet size is unlikely to need any change. If it does, then the change will be very small.
Idle and transition circuits almost always benefit from modification.
Many transition circuits feature 5 progression holes, 2 of which are very close. Closing one of these holes and creating a new, higher progression hole is of great benefit - it widens the operating range of the transition circuit and makes for a much smoother, less pronounced transition to the main circuit (which does not come in fully by the time the standard progression circuit has activated its highest hole). Such a modification must be carried out with great care and precision.
The standard idle and transition circuit cannot be described as excessively lean or rich - it does, however, always have lean holes.
The standard idle circuit tends to leanness, even at no/low load as rpm increases. A better compromise is achieved by a smaller idle air corrector hole. The idle air corrector is not normally considered to be a calibration part on the dcnf carburettor - the calibrated brass bushing may be pulled from the carburettor body and replaced by a smaller one which will need to be fabricated.
It should be noted that different distributor setups for different years and different markets affect what is required to get acceptable running. In general some of the tendency to flat-spots in low load and transition can be overcome by advanced ignition timing in the lower rpm range. Early European cars with twin distributors achieved this by use of a throttle microswitch.
Although some small increase in the size of the idle jet alone can yield noticeable improvements to the driveability of the car, anything beyond a small change is inadvisable and will lead to points of excessive richness.

Carburettor synchronisation
Synchronisation of the carburettors is straightforward and an iterative process. Idle synchronisation is standard. For part-throttle synchronisation, there are two important things to note. The bell-cranks in the linkage are crudely peened from the factory and develop wear. It is best to add a small tack weld to remove / prevent any play. With a single flow meter or other similar system, constant part-throttle flow can be synchronised but this is not adequate as it does not synchronise the far more important pick-up point. i.e. The precise synchronisation of both banks as they move off idle (or any other throttle opening) is the goal and this cannot be achieved by measuring steady-state part throttle airflow. One must use multiple flow meters (at least one on each bank) or, better still, mercury manometers to synchronise the two banks.

Airbox restriction
The intake air silencer, internal to the air cleaner assembly, may be excessively restrictive. In some cars, the silencer runs too close to the air filter, reducing the intake / filtering area drastically. This can be remedied by modifying the exit of the intake air silencer or fabricating a new one. This change is recommended even if one is not looking for performance gains - it will improve efficiency and air filtration. It will also require a check of high load high rpm mixture. As far as noise is concerned, removal of the air intake silencer not only leads to greater carburetteur noise, it also makes the induction noise of the right hand cylinders more noticeable at idle.

Fuel pump
The original Corona fuel pump is a sliding vane pump and works very well but is no longer available. Replacement fuel pumps, supplied by most vendors, including official suppliers, are not at all suitable, leading to reliability issues and sometimes running issues. If you have an original fuel pump, it is advisable to check fuel pressure at the carburettors. Sometimes it is necessary to add a calibrated restriction into the return line in order to achieve the specified pressure. If it is necessary to replace the fuel pump or if a points / diaphragm type pump is installed and an original is not available, then a fuel pump similar to the original should be fitted, that is to say a pump designed for constant running. A Carter high volume low pressure vane-type fuel pump is available. Points, interruptor or diaphragm pumps are inadvisable.

Steering rack
The original steering rack is a British-made rack and pinion by Camgears. It is very similar to a Mini steering rack with the following being the only differences:
The length of the rack bar is different.
The length of the track rods is different.
The rack body has been lengthened by two riveted aluminium extensions. These extensions are glued to the rack body with a "chemical metal" type epoxy.
While the steering gear is adequate, it is a component which is not well made and develops excessive wear quite quickly. The passenger-side rack bush (originally plastic) is the first item to show wear and should be checked regularly. Replacement with a bronze bush is common but the compliance of the original plastic bush is better in most circumstances.
Genuine new steering racks are not available.
Rebuilding a steering rack is entirely feasible, the main difficulty being to obtain good quality components. A normal rack rebuild allows for adjustment of pinion bearing preload as well as a crude adjustment of rack/pinion engagement / lash. A simple assembly and adjustment of components is not recommended without also properly checking the rack/pinion contact patch.
Original steering racks were lubricated with 80w90 gear oil. Newly manufactured mini steering racks and many rebuilt racks are supplied with a low viscosity grease. 0w grease works but oil is a preferable lubricant for the rack in all respects except for leaks!

Exhaust
Original mild steel manifolds, made by Ansa, are hard to come by. They are also not particularly well made and their primary lengths vary excessively. Weld quality is poor and intrusive. The head / flange junction is poorly matched with a notable and restrictive step down to the exhaust primary. Original exhausts usually featured sample ports (in a variety of positions).
Many replacement exhausts are available, most of which are of poor quality. Most replacement exhaust manifolds are manufactured in stainless steel and have an even shorter life than the originals. Many suppliers are selling stainless manifolds with welds which are not back purged and do not withstand the heat and vibration they are subjected to.
Our advice is to use only the highest quality exhaust manifolds. Tubistyle and Larini are reasonable. Even when using a modern gas analyser, it is always best for the manifolds to have sample ports.
Heat shields are essential - be careful of the originals which tend to disintegrate and may contain hazardous material.
USA specification exhausts have more extensive heat shielding, making them significantly more difficult to remove, refit and repair. Various early style USA catalysts and thermal reactors were used. These are often ineffective and can cause excessive heating.
Some exhausts will offer a very small performance increase. Proper port matching and better collector design are useful performance modifications. Better modifications would be more accurately matched primary lengths and a rear manifold which has longer secondary pipes. No exhausts are on sale with these characteristics.
Replacement of the front exhaust manifold requires removal of the right hand petrol tank, alternator, alternator support and dipstick tube.
Replacement of the rear exhaust manifold can be done by removing the handbrake crank mechanism and the exhaust silencer. It requires careful manoeuvring but does not require disconnection of engine mounts etc.

Wheels and suspension geometry
Original wheels were either 6.5J or 7.5J x 14". 16inch wheels (7J front, 8J rear) were optional toward the end of production. The driving and handling experience are significantly different on 14" and 16" wheels.
Staggered wheels (16") and modern tyres give very good levels of grip. Tyre choice in both 14" and 16" is quite limited.
14" wheels (same width front and rear) require positive camber front suspension.
16" wheels require around 1.5 degrees of negative camber on the front. Other geometry is similar but some consideration should be given to the greater levels of grip afforded by modern rubber, particularly with the high performance, lower profile tyres available for 16" wheels. Breakaway, in the dry at least, was very progressive on 14" wheels and XWX tyres. If possible, 16" tyre choice should be made to ensure that breakaway remains predictable and progressive.
Depending on use, it may be useful to substitute the original rear anti-roll bar with a 308 GTB anti-roll bar when using 16" wheels. This can suit the higher grip levels available although the loss of traction should be considered.

Gear Oil
Normally 80W90 gear oil is specified. API-GL5 or EP oil is not necessary and not really recommended.
There are many opinions on gear oil. Redline MT90 is a suitable oil and appears to give very good gear change characteristics, working particularly well to achieve fast synchronization as compared to many other oils in this gearbox. There are two oil drains and two oil fill plugs.

Headlight switches and relays
Headlights are not operated through relays and headlight column switches are expensive, rare and fragile. It is considered good practice to take electrical load away from the headlight switches by adding relays to the circuit.

Window winders, switches, relays
The window mechanism uses a cable wound around a drum, turned by an electric motor with a small worm gear. Often windows work slowly and erratically. Apart from making sure that the tracks and felts are in good condition, the following points are worth noting.
Grease in the worm drive gets old and hard. Before considering any other work it should be cleaned and renewed.
There was a factory update to relocate a cable guide / tensioner in order to take up excessive cable slack. If not done, this should be carried out, drilling a new hole for the guide.
All cars have an emergency window winding handle in their tool kit. When used, this must be fully inserted to disengage the worm gear, allowing free turning of the drum. The spring loaded mechanism which allows for the disengagement of the worm gear tends to corrode, giving excessive friction to the drum, even when winding with the motor. In order to remedy this, ensure that the worm gear can be disengaged easily with the handle and that it turns without undue resistance (it is always quite hard to turn). Apply penetrating oil and then light oil / grease in order to ensure that these components move freely. Lubricate from time to time via the hole for the emergency winder handle.
All electrical power for the window winder motors is routed through the window switches. This is poor practice. The contacts in these switches are small and prone to excessive resistance. Original switches are no longer available. It is advisable to use two relays per motor in order to ensure that full voltage and a direct earth are available at the motor and to prolong the life of the window switches.

Cooling system
These cars have a reasonable cooling system and should not overheat with standard components. The following are useful tips:
Ensure that the foam seals are present between the radiator and bonnet and at the sides of the radiator. These are essential to ensure full flow of air through the radiator.
Like many mid-engined cars of the period, careful attention needs to be made to ensuring the cooling system is free of air. Regularly bleeding at the radiator (with the header tank cap removed) is recommended. Some cars have a bleed screw on the thermostat housing. This is useful for bleeding after having drained a significant amount of fluid.
Many people replace the radiator fans with a more modern design. Often the modern fan motors consume significantly less current. Modern fans are shrouded and can be more efficient but beware that they also usually have a far greater surface area and that the shroud reduces flow through the radiator when not fan assisted. Original fans use a Lucas motor. These do not last particularly well (especially if not used often). Occasional partial disassembly for lubrication increases the life of the original motors. All parts are available to rebuild them although most of the brush packs are of later design and are very poor quality (the brushes have grooves in them and are retained by the circuit board itself); earlier brush packs have a properly designed metal housing for the brushes.

Clutch, flywheel, drop gears
Clutches in the 308 were deemed to have a short life although the main contributing factors to this are poor driver skills combined with a rather heavy pedal. The steel flywheel is also less forgiving of abuse than a heavier, iron flywheel.
Replacement clutches, including from official suppliers are usually of very poor quality. The original clutch is made by Borg & Beck in the UK. Since becoming part of the Firstline Automotive group, these clutches may come from one of two production facilities. Mostly they are poorly made and very far outside factory specs, notably the pressure of the pressure plate which is stated in the factory manual. Clutches bearing the same part number and marque but still made at the original plant are very much better, although not as nice as the original since they have a slightly different spec with excessive over-centre action. A clutch from Helix Autosport (now also an official Ferrari supplier) is a better quality option.
The steel flywheel can discolour, distort, craze and crack. Very light surface cracks are acceptable and when re-facing a flywheel, some small surface cracks may remain.
Great care needs to be taken when replacing the drop gears after clutch replacement. The original torque setting for the gearbox input shaft is on the low side and the locknuts can work loose. Careful over-torquing is advised (with the proper tool obviously).
Adjustment of the linkage and helper spring as per factory spec is important.

Cam timing belts
Opinions on timing belts are many and varied. Timing belts are generally reliable and simple to replace. Original manufacturer's service interval was 5 years but was subsequently reduced to three years. The 5-year interval is acceptable as long as the vehicle has not sat for long periods without use (and with the usual provisos about ensuring that leaks of oil or water do not contaminate the belts.
When replacing the timing belts, some attention should be given to the condition of the tensioner mechanism and bearings. Replacement bearings are often of poor quality, including those from official suppliers. Hill Engineering bearings are a good quality replacement. Attention should also be given to the jackshaft (intermediate shaft) bearings and oil seals. Any play or leakage, even minor, should be rectified when replacing timing belts. If it is necessary to replace jackshaft bearings or seals, it is a perfectly acceptable repair to replace the outer bearings (and seals) in situ, leaving the original inner bearings which have an excellent life expectancy. Be aware that there are two types of bearing and seal arrangements for the jackshafts.
Cam belt covers are adequate although they may be improved by the addition of a backing plate, thus reducing the chance of debris falling into the timing belt mechanism.
When replacing cam belts, always replace accessory belts and systematically change the aircon belt tensioner bearings. They don’t last well and are very cheap.

Water pump
Water pumps are often stated as being unreliable and it is true that Ferrari changed the seal design many times over the production life of these pumps and that they increased the bearing size in successive attempts to increase reliability.
Pump bearing failure is rare unless the pump seal has failed. This is true even for pumps with small bearings (most of which have now been replaced with large bearing pumps.)
Pump bearings are quite small and the tension required on the thin accessory belt is high - this does put the bearings under significant radial load but not enough to cause premature failure. Long periods without use and improper corrosion inhibitors will reduce pump life. Excessive tensioning of the accessory belt also reduces pump life significantly.
Newly manufactured water pumps are all of very poor quality. Without exception, it is advisable to rebuild an old pump when necessary. (There is one "performance" pump available in the USA which is of adequate quality although still not as good as the originals.)
When replacing pump bearings, good quality C3 bearings are advised. It is always better to use the later, larger design of pump body with the larger bearings.
Water pumps originally came with a two part seal. Later two-part seals have a smaller diameter working seal, reducing the speed of the contact surfaces. This is the most reliable of the two part seals (the same reliability as the best one piece seal). It requires a specific impeller design with a recess on the back. It also uses the "smaller" shaft diameter. Installation of this seal is easy but finding a good quality seal may not be. They are not available through official suppliers.
Unitized seals (often referred to as single piece) of the latest design are also reliable. Source from a good quality manufacturer. MTU of Italy is the original supplier. These use the later, small shaft diameter and the impeller with the flat back face. Installation requires the use of a special installer tool with the correct depth of step.
Pump bodies are sometimes modified in order to take later seals (at one point there was a service bulletin recommending this). Some have been modified to accept different seals. Modification of the pump body and the use of other seals is fine in principle but beware the quality of work. Some specialists provide rebuilt pumps with various other additions such as "triple bearings". None of these provide any benefit whatsoever and usually indicate a lack of understanding of the pump's failure modes.
Water pumps should be checked routinely but do not need routine replacement or rebuild. When rebuilding a pump, some benefit is gained by smoothing the passages where coolant abruptly changes path.
A standard water pump, in good condition with a later (smaller) two-part seal or a later unitized seal is a reliable item if the accessory belt is not over-tightened.

Speedometer
The electronic speedometer sender can be prone to failure. Although this is theoretically a sealed unit, it can be opened easily. Failure is almost always remedied by removal of moisture and corrosion or repairing dry joints by re-soldering them. The sender is subjected to moisture, heat and vibration.

Oil consumption
Some oil consumption is normal. Regular use of the vehicle does help keep oil consumption to a minimum. XXXX / litre is the official maximum allowed but there’s nothing much wrong with a bit of oil use on a motor that otherwise runs very well.
Oil leaks are common. There are 7 lip seals on the front of the engine, 2 or 3 on the back and plenty of pipes, gaskets, o-rings and seals. An engine can and should be reasonably oil-tight. A reputation for leakiness has been wrongly earned because budget maintenance (just replacing a single leaking seal) leads to a cycle of leak-chasing. Installation of some seals is difficult without using a proper tool.

Rear brake callipers
The ATE rear brake callipers function in the same way as those used on Porsches and Alfas of the period. The self-adjusting mechanism can fail although this is usually the result of abuse rather than poor design.
When fitting new brake pads, the adjuster mechanism is used to retract the pistons (it’s slightly different for inner and outer pads). There is a pad to disk clearance which should be respected when refitting pads however the official procedure fails to mention the following important precaution. When using the adjuster to move the pad into closer contact with the disk, it must be turned until the approximate clearance is obtained and then locked. It must not be backed off to increase a tight clearance. At least, if this adjustment is backed off, then it must be re-advanced so that the last movement of the adjuster prior to tightening the locknut is to decrease the clearance. Once adjusted in this manner, even if the clearance is approximate, the automatic adjustment mechanism works to obtain the correct clearance.
The handbrake performance was poor from new mainly because acting only on the inner pistons is a poor design. Ensuring that the cables, pulleys and pivots are properly lubricated and in good condition will obtain adequate handbrake performance (just about).

And now you’ve just got to hope that nothing else that will go wrong with your car! Overall, these cars are reliable and simple. We haven’t mentioned the door locking mechanism, windscreens, steering u/j’s and all manner of other things but it’s more important just to regularly drive it!