Before you start

 

If you've just bought the car, or have had little time checking things, now is the time. I'll make a list of pre-tuning jobs that should be carried out to ensure the engine's going to benefit the most from fuel & ignition tuning.

​

Considerations before starting any engine tuning are important, to make sure that you're not wasting your time, and also so you know what you want to achieve, and how to achieve it. For example, an engine that has a leaking carburettor base gasket would be pointless to tune, as any fuel mixture changes seemingly required would be masked by the extra air being drawn in under the metered air through the carb(s). Equally, an engine with a burnt out exhaust valve with low compression on one cylinder would never run correctly, and so mechanically any engine needs to be fully sorted before venturing on to the final tuning.

Pre-Tuning Checks

​

• Compression - how sound is your engine?
  Check the compression to make sure you have no more than roughly 15% difference in readings between all cylinders. Any low reading for one particular cylinder needs investigating. Reasons may be simple such as rocker arm clearance too small and an adjustment needed. However I have seen plenty of older engines being run on unleaded fuel for a long time, and valve seat regression has taken place. The valves wear into the cylinder head, and the clearance between the rocker arm & valve gets smaller as the wear increases. Eventually the valves won't close fully and the engine will be gutless. Exhaust valves always wear more than inlet valves, even where hardened valve seats have been installed. This is due to the heat and carbon deposits wearing the valves & valve seat inserts. 
  Other reasons for low compression on one cylinder can be a burnt out valve (exhaust valves can crack & a split will appear, lost compression will occur). Piston ring wear or damage, cylinder head issues, worn bore due to a coolant leak within a cylinder (or an overfuelling issue) etc. Some problems will mean a lot of work is needed, others are more simple, Without good compression the combustion process is never going to be optimal.
  
   

• Fuel System - is everything working as designed?
  A carburettor stripdown is a wise idea, especially if it's not been done recently. You'll find more info in the fuel system section for anything not covered here, but generally you'll want to make sure that all the carb components are in good order, match the specifications according to the data for your engine, and that all areas of the carb work as designed. Strip the carb down & remove the idle jets, air corrector/emulsion tube/main jet assemblies, also remove the float to get to & remove the float needle valve & seat, and check for blockages, dirt, and also make sure the size of jets etc matches the data for your engine. If anything is different, perhaps someone has already had a go at tuning the engine, or possibly has fitted a similar carb but from another vehicle. Of course the engine may have been modified, and this may not be noted anywhere if the work was done by a previous owner. If this is the case, you may be covering old ground without knowing it, but unless you can be sure the engine has no issues, it would be wise to recheck the tuning so you know you're getting the most out of the engine. Here's a Weber 40DFI that I removed, and found the base had warped due to age/heat & poor design. There was a massive air leak which made tuning impossible. The red area shows the extent of the warping against the steel ruler.
  
   

​















 

• Ignition System - be 100% sure it's ok!
  Ballast or Non-Ballasted Ignition? - There are many issues with the ignition that may not (at a leisurely glance) be obvious. I see so many incorrect ignition coils fitted to older vehicles these days, and I think it's a combination of lost knowledge, combined with online sales of car parts lacking the human touch. Remember the 1980's & 1990's when your average local car parts shop would have someone in there to check what was correct before selling it to you? Ok perhaps not all of them were good even then, but on the whole it would be easy to check if a part was correct while in the shop. Anyway, as there could be a ballast resistor fitted to your TVR, you'll need to decide whether the igntiion coil is correct. The resistor is used in the circuit feeding ignition voltage to the plus terminal of the coil (marked SW for switch, or 15 on some coils e.g. Bosch), The negative terminal can be marked CB (for contact breaker), or 1 (again on Bosch Coils). This resistor is needed as the ballast type ignition coils are run at approx 9 Volts, as opposed to 12 Volts. When the starter motor is turned, a 12V bypass circuit feeds the Ignition Coil directly, and boosts the 9V coil to give a better spark. This only lasts as long as the starter is turned (normally). When a ballast type coil is fitted to a non-ballasted ignition (which runs on a constant 12V), then the coil is overloaded all the time the ignition is on, resulting in faster points (contact breaker) wear, possible condenser failure, and coil failure due to overheating. I've seen coil terminals melted as a result of this in a couple of cases.
  To test if the car has a ballast resistor, use a multimeter set to DC Volts, and check the voltage at the coil + terminal. If it's 9V then the car has a ballast resistor, if it's 12V then it doesn't. A further tip to help you on this is that depending on the ballast resistor (alternatively a resistive wire), some ballasts have a "clever" resistor which heats up once the ignition is on, and output votage will reduce from an initial 12V down to 9V once warm. Another note is how the resistor circuit works, especially on the Essex V6. The starter motor has a second small terminal (in addition to the trigger terminal), that will output 12V only when the starter is turned. This is linked to the coil + terminal and is a momentary fed voltage. The usual 9V feed comes via the ballast and is a constant feed.- thus providing a normal supply at all times other than starting.
  I prefer to do away with the ballast, as it's another part to fail, and with a well set up engine isn't really needed...especially if a high power starter has been fitted.
  Finally getting to the point, the Coil fitted should be matched to a ballast or non ballast system. The ballast resistor is approx 1.5 Ohms resistance (some types vary from this) - and a coil for such a system should generally measure 1.5 Ohms. A non ballasted system will require a 3.0 Ohm coil. Fitting a non ballast coil to a ballasted ignition system will result in a weak spark, due to the coil getting 9V instead of 12V. This can result in misfiring at higher engine RPM's and loads, and so checking the coil type is at the top of the list.
  
  Points or Electronic Ignition?
  Originally a Ford or Bosch Distributor was fitted to the Essex V6, and both had a points & condenser setup. Electronic Ignition only became a production item when the Cologne V6 appeared in the early 80's.
  I will explain points setup in the Ignition section, but will just say the points should be set first approximately by feeler gauge, and then fine tuned by setting the dwell angle using a suitable multimeter. Optimum setting provides the optimum spark. The dwell angle allows the coil to produce the best spark possible and is really just the amount of time in degrees that the points are closed, hence charging the coil for the next HT spark. The limitations of points means that at higher revs, the points can start to bounce & the spark can suffer. The dwell angle is also set at idle and is not going to be optimal right through the rev range. 
  Replacing points with electronic ignition means that there is no longer a points gap to set (some systems utilise the points as a simple switch however, more later), therefore reliability is improved. Also the dwell is automatically set by the ignition, thus making a better spark for the whole range of RPMs. There are three main of types of electronic ignition systems - optical trigger, magnetic trigger, and points based signal. Here's a list of the various types:
  
  Optical Trigger
  Lumenition Optronic
  Lumenition Performance Optronic
  
  Magnetic Trigger
  Aldon Ignitor I
  Aldon Ignitor II
  Lumenition Magnetronic
  Sparkrite SX500
  
  Points Based
  Sparkrite SX4000
  
  Some of the cheaper kits above have issues with fitment to certain distributors. I've found that some don't allow the vacuum advance to operate and have had to return them. I can vouch for Aldon & Lumenition kits and would recommend either as a first choice. Not all of the above may have a kit to suit your vehicle, I'm currently working on an update to this page so can provide more specific info.
  
   

• Cooling
  As covered in the cooling section, make sure the correct thermostat is fitted, that the electric cooling fan(s) cut in and out at the correct temperature. If the fan continues to run without switching off, it could be the engine is too hot while stationery. Modern cars usually have two speed fans, and for example low speed will cut in at 93ºC, high speed at 99ºC. Some have one fan at the lower temp & both at the higher temp. From this you'll get a good idea of the max temp. you'll want before overheating & poor idling starts. Ideally the fans will cut in and out, cutting in to loer the temperatureas & cutting out once the lower limit has been reached. With an engine overheating, tuning is not a good idea as at higher temps. the engine won't be running with "normal" fuelling - V engines suffer more from fuel percolating as the carburettor is sitting in the centre of the engine with little in the way of cooling.
   

• Charging
  Alternator output at idle should be over about 13 Volts on an old Lucas type alternator. They rise to about 14.4V above idle, but were never that good at low engine speeds. Just make sure you're getting something over 13V at idle.
   

• Exhaust
  The standard TVR designed exhaust for the 3000M isn't particularly large bore, and was a compromise between performance, ease of fitting, and ground clearance. The manifolds in particular can be quite restrictive for airflow, and there are a couple of aftermarket systems that have equal length manifolds to improve on the standard system. I've been told that you could lose 15-20 bhp in the standard system. Tuning your engine before an exhaust change (i.e. to a better flowing system) will cause changes to the air/fuel mixture, and therefore a re-tune would be needed to maximise performance.
   

• Brakes/Suspension/Steering/Tyres
  All of these need to be well maintained for any performance car, especially so after performance mods to the engine
   

• Insurance
  Don't forget to tell your insurance company of ANY tuning or general modifications, no matter how small you think they are. Include braking mods, suspension, air filter, etc etc. If you don't, you'll be fine until you have a claim/accident, and then you'll soon find out they'll not cover anything and you're on your own. It could end up in a hefty loss, even you lose the car completely if written off - without any cover, no matter whose fault it was. The insurance company will send a loss adjuster to view the car, and they literally check everything down tyre pressures, condition, even if a radio has been fitted (UK Insurance - can't be sure for other countries). TVRs are mostly in the classic car and performance car bracket, and so seek specialist insurance to cover your car. In some instances the police will take the car & check for roadworthyness, including any non standard mods. It's just not worth the risk.