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Welcome to the Aston Workshop news section. This section will update regularly, enabling you to keep up to date of changes and new information relating to the Aston Workshop and the Aston Martin Marque.
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Q & A
I have a classic Aston Martin and I am concerned that my car may never have been modified to run on unleaded fuel. What are the facts and what do I need to do?
Answer:
It all depends on which model of Aston Martin we are talking about, as the later cars were unleaded compatible from the outset.
Virage and later cars
All cars manufactured by Aston Martin since the introduction of the Virage were designed to be fully unleaded compatible. Indeed, as they are catalyst fitted, they should only be run on unleaded fuel. There are therefore no concerns with respect to these cars and no action is required.
V8 Pre-catalyst from Oscar India, series 4 and Vantage V8
As a general rule, all cylinder heads were fitted with hardened valve seats at the outset and valve materials were excellent quality. Provided that the engine is restricted to running below 3000 to 3500 revs on a continuous basis, it is very unlikely that problems will arise through using unleaded fuel and that any overhaul is unlikely to be needed unless for other reasons. However, for track day events or to use the car for prolonged high speed cruising, it is advisable to consider undertaking an unleaded conversion and cylinder head overhaul.
Series 1 to 3 V8s prior to 1979
These cars will run on unleaded fuel, but prolonged use without additives is inadvisable. The long term answer is a full unleaded conversion, but care is still required as the reduced 95 Octane rating of standard unleaded may cause pinking and running on to occur.
DB4, DB5 and DB6
These cars will happily run on unleaded fuel without modification for a restricted period provided that any use is gentle and engine revs are restricted to below 3000 on a continuous basis. However, as leaded fuel is all but unobtainable, long term use of unleaded fuel may cause problems. There are two possibilities. One is to use additives and mix with the fuel. Alternatively, the long-term answer is to fit hardened valves, valve seats and guides. An increasing proportion of these engines have now been modified, so before embarking on a cylinder head conversion and overhaul, do check and see if there is evidence of this conversion having already been done.
DB 2/4 MkIII
Engines fitted to these cars are given a prefix of DBA or DBD depending on whether they are twin or triple SU fitted. The cylinder heads fitted to these models has a somewhat chequered service history as they have a tendency to experience cracks in the cylinder head between exhaust valve seat and spark plug boss. When these were manufactured, they were given an increased diameter of valve, and because of the clearance between inlet and exhaust valve seats and spark plug boss, there was not sufficient metal to allow the use of a hardened valve seat. Consequently, the seating for the valve is directly on the cylinder head casting. Some owners have managed to modify their cylinder heads and have fitted hardened valve seats, but no one can guarantee that the fitment will be problem free. Too many cases of cracks appearing and seats dropping out have occurred and it is therefore not a recommended solution. In any case, the DBA and DBD cylinder heads are known for cracking and while some have successfully been welded, others have failed. There is an alternative, which is to fit an aluminium cylinder head. These can be sourced through the DB2 technical adviser to the Aston Martin Owners Club, Mr David Wheatley or through a recognised Aston Martin specialist such as Aston Workshop. Known as the Alperform cylinder head, they can be provided in standard, fast road or race form depending on the desired level of tune and are a complete long term answer to all known problems.
As an interim measure, use of additives can be considered. Names of fuel additives that owners have used on a regular basis are at the foot of this answer.
DB2 and DB2/4 (other than DB MkIII)
The VB series of engines were all fitted with conventional valve seats unlike the later cars. They require modification for long term use of unleaded fuel, especially if engines are used for prolonged periods in excess of 3000 revs. The modification consists of fitting hardened valves, seats and unleaded compatible valve guides. The alternative is to use additives but as before, these ought not to be considered a long term answer.
Octane rating – As a general rule, all engines can be tuned to run on a minimum octane rating of 95. However, Vantage spec and higher compression engines when used with standard ignition timing settings can pink or be subject to running on after turning off the ignition. The quick solution is either to slightly retard the ignition until pinking is no longer present or use 97 or better Octane fuel. The best recommendation is try 95 octane fuel and see if a problem exists. Use of higher Octane fuel is pointless if there is no evidence of pinking as such.
Additives – Aston Workshop will provide no recommendation with respect to the best additive to use with unleaded fuel. However, additives that Aston Workshop is aware of being used on a regular basis by its customers include:
i.Castrol Valvemaster Plus. This also assists in slightly raising the octane rating
ii.Millers VSP Plus – This also assists in slightly raising the Octane rating
iii.Tetraboost – Unlike the additives above, these add small quantities of lead back into the fuel and adding this therefore recreates many of the advantages of using leaded fuel. There are environmental concerns and it is very toxic. Considerable care is required inhandling this substance, so do consider carefully if this is acceptable for you. In the minute quantities involved in use, it is very unlikely to have an environmental impact of any consequence. Again, there is a slight benefit in fuel octane rating.
Cylinder Head conversions – Aston Workshop can undertake all of the cylinder head conversion work to make engines unleaded compatible. However, before commissioning such work it is worth considering a number of key issues:
i.Is there a need for disturbing the engine for other reasons, such as high oil consumption, low oil pressure or chronic cooling problems. Undertaking an unleaded conversion as part of an engine overhaul is generally all part of the package and is by far, the most cost effective time to do the conversion
ii.When removing the cylinder head it is always good practice to renew top and bottom timing chains at the same time.
iii.Vantage spec engines may require 97 Octane fuel or better. The implications of this need should be considered.
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