Roy's Matra Enthusiasts pages
FAQ's: Frequently Asked Questions
- I have a Matra Djet, 530, Bagheera, Rancho or Murena. What fuel do I use?
These cars were designed and built when petrol had a higher content of TEL (Tetra Ethyl Lead) which provided valve seat protection, upper cylinder lubrication, and high octane levels. However, when we were forced to go the catalytic convertor route, this had to be reduced as TEL is 'poisonous' to catalytic convertors and makes them useless. Please note, it was not harmful to humans as many tried to make us believe as it could not get in to the blood stream since it could not be broken down by the body's enzymes. Records show that lead in blood levels in this country had been dropping consistently from 1933 to the present even though TEL content had risen consistently from 1925 to 1970 and there are far more vehicles on the roads today too, which both go to prove the two were not linked. The real high lead-in-blood figures came from the States where they still used a high percentage of lead water pipes, lead in household paint, etc. at the time. In fact it is the present low-leaded, so called 'unleaded' fuel (but it does still contain some lead) that IS harmful to us as it contains at least five elements that are known to be carcinogenic; so if you get it on your hands or skin, wash it off immediately, and try not to breathe in any of these petrol fumes.
When we changed to low-leaded, for a short time we had pumps that provided what was called 'LRP'. This Lead Replacement Petrol was actually Super low-leaded petrol with some lead replacement additive. There were several types of additive, but this LRP has now disappeared from the forecourts, and if your engine needs these additives, you must add them yourself. So the real questions are 'Does my engine need any additive?' and 'What octane do I need?'
If your engine has a cast iron cylinder head, the chances are it has the valve seats cut directly into the cast iron. The TEL used to leave a small coating on the seats which protected them from damage. If you use modern low-leaded petrol there is insufficient TEL to protect these seats and they will be damaged and the resultant seat regression will reduce the clearances to zero, causing loss of compression, difficult starting and poor running. To prevent this you need either to add some lead substitute in with your fuel, or have the cylinder head modified with hardened valve seats.
Engines that have aluminium cylinder heads already have hardened valve seats, since the alloy is too soft and the seats, if cut directly into it, would be destroyed immediately. Most modern engines with alloy heads from say the seventies onwards, have seats that are already hard enough, as confirmed by Brico - a manufacturer of these hard valve seats. So you do not generally need the lead replacement additives. However, an occasional dose may be beneficial for the upper cylinder as other components used to be helped by TEL as well.
If you have a really old engine that, unusual for its time, was made from aluminium, then it is possible the valve seat inserts are not hard enough for the modern low-lead fuel, so it might be wise to get the inserts checked and/or changed.
Fuel octane. The two grades currently available in Europe generally are 95 RON often called 'Premium' and 98 RON usually called 'Super'. Since most engines from the sixties and seventies were fairly high compression and often had sharp edges in the combustion chamber, they required at least 97 octane, so today you need Super. If your engine is low compression, say 8.5:1 or less, then you should be fine using 95 octane. If you cannot find any Super as I have sometimes found to be the case, then you need some octane booster for use with the Premium grade. You could retard the timing, if it was easy but on most this is no longer a simple operation like when we had the knurled wheel on Lucas 25D distributors! So why not carry some octane booster for emergencies. You might think you could drive more gently, but if you have to climb a steep hill or overtake something, this is not really an option, and pinking and detonation can seriously damage your engine.
Finally, there is still some leaded fuel available. Under EC regulations a small percentage of 'proper' leaded fuel is allowed to be sold. It is usually available from private retailers as the large conglomerates do not want to deal with such small volumes. So companies like Bayford Thrust still supply this high octane leaded fuel but at a cost. It is often as much as 1.5 times the cost of Premium low-leaded. Before you say, 'Well I'm not paying that much!' consider how much mileage a year you cover in your classic, how much fuel you will use, and how much that will actually cost. If you have to buy additive, maybe with booster, you have to add this to the cost of the fuel at the pumps, and have the hassle of finding it and carrying it. Proper leaded may not actually work out that much different.
Djet - May requires hardened valve seat inserts, and needs Super grade.
M530 - Cast iron heads so definitely needs hardened inserts, but may run fine on Premium.
Bagheera - Alloy head and high compression and should be run on Super.
Rancho - Alloy head but low compression so possibly will run fine on Premium.
Murena - Alloy head and high compression so requires Super low-leaded.
Espace I - Alloy head and high compression. Renault recommend Super yet I have found mine will run fine on Premium, possibly owing to the better combustion design and fuel injection on its modern engine. The carburettor model may be different and need Super.
If you run any of the above on Premium and it 'pinks', then you should run it on Super. The problem is that it is difficult to tell pre-ignition (pinking) from detonation and pinking often causes detonation anyway. Detonation will damage your engine - it can blow holes in the pistons!
Provided the engine is running correctly with no faults, the timing should be standard. Make sure the auto and vacuum advance are working correctly. Remember since we do not check/adjust/replace points anymore, most people forget the other service item that should have been done at the same time - lubricating the centre of the distributor shaft, which was necessary for the bob-weights, and if this is not done the auto advance can and does seize up. So make sure the mechanism is free and you lubricate that at least once every 15,000 kms.
Also note, no amount of time will harden soft seats or valves! It is down to the material used. If you ever find the valve clearances keep closing up, then it implies the seats are wearing and you will probably need to replace them.
- The fuel pump on my 2.2 Murena is leaking. Where can I get another?
The original fuel pump was an AC Delco 461-26 and had a crimped body around the diaphragm. They used to fail and leak from here and there was no way to repair them. You should replace them, and you can either use the original number above to obtain a replacement, or try the Peugeot-Talbot 16205900 or the Mopar No. VFP212. With any replacement, check that the operating rod is exactly the same length (42 mm from flange to tip). There have been some that are slightly longer, and they won't work. As there is already a heat insulation spacer fitted between the engine and pump, you can't fit another spacer, so you would need to shorten the rod back to the original length or fit a slightly thicker spacer. Another option is to fit an electric pump, but if you take this route you should make sure to wire it with a safety device. All manufacturers fit an inertia switch so that in the event of an accident, the pump does not continue to pump fuel, possibly on to a fire!
If you need a fuel pump for the 1.6 or 2.2 engines see my parts page for a part number. If you have difficulty with the 2.2 type contact me as I have some new ones.
While mentioning fire, it is worth pointing out that you should NEVER fill the Murena fuel tank immediately before putting the car away in a garage. The problem is that fuel just pumped into the tank will be cold and the engine bay will be hot. Therefore the fuel will expand as it warms up, and if the tank is full, it will overflow onto the floor just beneath the driver's seat area, if it has the original vent valve in the filler pipe. This pool of fuel will give off fumes which are highly combustible, and are therefore a danger to causing a fire. It is better to leave the tank low and fill it just before starting your journey.
One good modification on the last 'S' models was they moved the vent valve to the top of the fuel tank. Anyone can do this same modification, which will benefit in a number of ways, so if you are interested, see my technical article on the fuel system.
- My fuel tank sender unit has corroded/broken. I can't get another, so what do I do?
The fuel tank sender unit has not been available for some time, so if yours has corroded and fallen apart, or does not work any longer, you will need to either get it repaired by a specialist or replaced with a universal type sender adapted to fit the Murena tank. The problem this leaves is matching the movement of the the tank float and resistor to the fuel gauge in the instrument panel. Fortunately there is now a small electronic device that can be set to match any sender to any gauge, which is designed and manufactured in the U.K. available from Car Builder Solutions (CBS) as code GMatch, or direct from Spiyda called Gauge Wizard 4. (www.spiyda.com)
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This was last updated 31st August '21