The opinions expressed here are entirely my own, so please use any advice on your own risk!
The Essex engineThe V6 engine that was used in the TVR 3000M is from Ford and is called Essex. The Essex have been used in several Ford cars as well as many kit cars and cars from specialist manufacturers as TVR, Marcos, Ginetta, AC, Gilbern, Reliant and others.
History and evolution of the Essex engine
The first car that was equipped with the Essex was the Ford Zephyr/Zodiac in Mark 4 version, these cars came 1967. The next Ford car that used this Engine was the Ford Capri 3000 that came 1969, later the Ford Granada/Consul series was introduced in 1972. TVR used the Essex first time in 1969 in the TVR Tuscan V6 and later in the 3000M 1972. The last Ford car that used this engine was the Ford Transit van in 1982.
The first version of the Essex engine came in either 2.5 litre, (2495 cc) or 3.0 litre, (2993 cc) capacity, both have existed in high and low compression variants. The engine was updated in 1972, by changing the camshaft and the shape of the intake ports the power increased slightly. A version with higher capacity of 3.1 litre, (3081 cc) was used in the Ford RS3100 Capri. The X-pack version of the Essex used heads with bigger valves and either triple Weber DCNF's or a larger single Weber DFI carb.
Ford original specifications for high compression 3 litre engines
|Power DIN BHP
||136 as standard, 142 in TVR 3000M due to better exhaust manifolds
||Used in TVR Tuscan V6
||New cam and cylinder heads
||Bigger valves, triple Weber 42DCNF
||Bigger valves, Weber 40DFI
Two TVR specific special version of the Essex engine was offered in the 3000M, the most commonly known is of course the Turbo version. The TVR 3000M Turbo that came in 1976 used a broadspeed turbo version of the Essex engine, only 20 of these cars where made together with 30 Taimar Turbo and 13 3000S Turbo.
What is less well known is the conventionally tuned engines with bigger valves that where offered only on customer request, I don't know how many of these cars where made.
||Big valve, BV
|Power DIN BHP
Tuning the "Essex" engine
The "Essex" is a "Heron" design engine with an almost flat cylinder head and the combustion chamber in the piston crown. It is very "oversquare" engine, cylinder diameter is 93.67mm and stroke is 72.41mm, ideal in many aspects for high power and high revs.
In standard form the "Essex" engine give relatively low power, originally 128 BHP from 3 litre or ~43 BHP/litre. The cylinder heads where modified in 1972 and with the addition of a different camshaft the power increased 8 BHP, but even the later heads flow poor in standard form and the valves are also unusually small.
A good thing with the "Essex" is that it is quite easy to get a substantial power increase by normal tuning, actually much more than what is possible when tuning a modern engine, the reason is that the "Essex" as standard have a very low state of tune.
By just changing the camshaft it is possible to get about ~15 BHP power increase, if more than this is wanted the cylinder heads must be modified. about 200 BHP is quite easy to get from an "Essex" but to achieve more than this it starts to get more difficult and also very expensive.
Unfortunately all tuning parts are quite expensive. Parts are however still available from both Burton Power and Ric Wood
One of the first thing that should be done when tuning this engine is to change the ignition system if the original breaker points are used, for a 6 cylinder engine reving in excess of 6000 rpm a breaker point systems doesn't work very good and will not keep the optimal timing point for long, (it is like having a four cylinder engine reving 9000 rpm using breaker points!). Lumenition are producing an optical replacement system and this can be recommended.
Next step can be to change the camshaft, Cam shafts are still available from Kent Cams, Piper and Burton Power, A mild road cam as Kent V61, V62 or V63 can be fitted without any other modifications, all are suited for otherwise unmodified engines and will give a power increase of up to 24 BHP according to Kent cams. See table below for characteristics
* Note! the power increase figures given are from Kent cams web site, it is really doubtful if it is possible to achieve so much power increase with just a cam change, maybe 2/3 of these values are more realistic.
||Power increase BHP*
||1000 - 5500
||No loss of low RPM power
||2000 - 6500
||"Wannabee" race cam, heavy loss of low RPM power
||1500 - 6000
||Best choice for street, good mid range power
V63 is probably the best all round cam for use in a road car, it gives a substantial power increase compared to the standard cam and the power is available at a wide RPM range. I can not recommend V62 for use in a road car, even in my very light car the loss of low and mid range RPM power is really noticeable and actually I am achieving better acceleration figures using the V63 than with the V62.
V62 feels very fast as it gives very high power at high RPM but this power is not really useable on the street.
V61 would be a good choice for use in car with automatic gearbox as the power loss at low RPM is almost not noticeable.
Note that if the camshaft is changed the ignition advance should ideally be changed also, cam shafts with longer duration usually need more initial advance and an engine that breaths better also need less maximum advance. Modified distributors are available from Aldon. For more about modification of distributors see: Dave Andrews Web site
Next step is to start modifying the cylinder heads, stage 1 heads use the original valves but the inlet and exhaust ports are modified for better flow, there are also other heads available with various valve combinations. Full race heads easily flow 50% more than standard unmodified ones.
Some modified cylinder heads for Essex V6
||Original valves, ported
|Burton full race
||Also available from others
|Ric Wood alu heads
With stage 1 heads the original carburetor can be used but for stage 2 and onwards it is better to use a bigger carb for highest possible power. An original Ford X-pack conversion used stage 3 heads with a Weber 40 DFI carb and the standard cam, this combination gave ~175BHP.
At this point it seems in its place to mention a bit about carburetor tuning. In many cases when tuning an engine and changing the carburetor for a bigger one the fuel consumption increases considerably. Most amateur tuners assume that increased fuel consumption is something that is to be accepted and they don't try to do so much about it. It is indeed expected to get some increase in fuel consumption but anything extreme should be considered abnormal and it pays off to find out what causes this condition.
When the Weber 40 DFI is used on the Essex engine the fuel consumption usually increase substantially, I will here explain some of the reasons why this condition arises and ways to correct it.
In Weber performance carburetors such as the DFI there are several different circuits in order to adjust the fuel to air ratio for different load. At idle the fuel/air mixture is supplied trough a hole below the throttle plate, the amount of fuel/air mixture can be adjusted by the idle mixture screw. When the throttle is open slightly more progression holes located above the idle mixture hole is gradually coming into operation and supply the air fuel
mixture. Then when the throttle plate is open even more the system using the progression holes stop operating, (as the vacuum drops when the throttle is more open) and fuel air mixture is supplied by the axillary venturi trough the system consisting of the main jet, the air corrector jet and the emulsion tube.
What most people fail to realise using a Weber carburetor is the importance of the idle progression system which heavily influence fuel consumption and the same time have small effect on the peak power on the engine. By adjusting this circuit it is possible to tune fuel consumption for cruising conditions. The items that are possible to adjust is what is somewhat wrongly called the idle jet and the air idle jet size.
More advanced is to change size of the progression holes or to modify the edge of the throttle plate in order to bring in the progression holes in operation earlier or by drilling small holes in the throttle plate in order to delay the operation of the progression holes.
The 40DFI as supplied for use on the Essex V6 is equipped with the following jets, (at least mine was).
Air corrector jets
Idle fuel jets
Idle air jets, (fixed)
When used as this on an Essex the engine the fuel consumption is very high and when inspecting the spark plugs they are very dark indicating a very rich mixture. What is also common is that the spark plugs in the 2 middle cylinders are darker than the rest indicating that the fuel mixture to these cylinders is even richer than to the others. The probable reason the jets where selected like this is to minimise the risk of having a lean mixture leading to burned pistons and/or valves. It is understandable that the ones responsible for selling these carburetors doesn't want to risk having the users ruining their expensive tuned engines so the carburetor is jetted deliberately on the rich side.
It should be mentioned here that I removed the W shaped metal bracket that is mounted on the isolating manifold gasket as this hinders airflow, I retained the gasket itself as it usually is good to have the carburetor mounted a bit above the manifold floor.
There are 2 separate things to correct in this case, one is the difference between the cylinders and the other one is the overall rich mixture.
The main reason why the 2 middle cylinders is running rich is not because they get more air/fuel mixture as such but because they get more fuel than the other cylinders, the mixture is richer than in the other cylinders. Liquid fuel as is always present to some degree on the manifold floor is mostly flowing into the middle cylinders making the mixture richer than in the others.
One way of correcting this is to mount some kind of fuel dam preventing the fuel entering the middle cylinders or by cutting slots in the manifold floor directing the fuel more to the end cylinders. As it is
difficult to cut slots all the way to the end cylinders I have mounted fuel dams made of 6mm alu rods glued to the manifold floor, the dams are mounted in such a way that they hinder liquid fuel to flow into the midlle cylinders. The theory behind and the procedure is described clearly in the well known book "Four stroke performance tuning" by A Graham Bell.
With these fuel dams in place the spark plug colour in my engine did get more even but still very dark so I reduced the idle fuel jet to size 55, the idle jets actually more control the off idle mixture so the name is a bit mis-representing, the actual idle mixture is adjusted with the idle mixture screws.
It is possible to check if the idle fuel jets are of correct size by checking how much the idle mixture screws need to be adjusted for best idle, it shall be at between 1 and 1.5 full turns out. If it is less then 1 turn the idle fuel jet is too large and if it is more than 1.5 turns the idle fuel jet is too large. The correct size of the idle air jets can be checked by first adjusting idle to the best possible setting with the idle mixture screws, then the idle speed should be increased to ~1500 - 2000 RPM. If now the revs increase when the idle mixture screws are screwed in 1/4 turn the idle air jets are too small and vice versa if the revs increase when the idle mixture screw is screwed out the idle air jet are too large. If the idle air jets are of correct size the rev should drop if the idle mixture screw is screwed either in or out.
The idle air jets are fixed in the DFI but as I found them to be too small in my case I carefully drilled them 0.2mm larger to 1.7mm. I also reduced the main jets to size 180 and later to 170 as I still got dark plugs at high speed cruising. I didn't change the air corrector jets at that time as they are critical in order to avoid lean conditions at full power and is more difficult to select without the car on a rolling road. When I later had my car on a rolling road the air corrector jets where changed to size 130 this gave highest power, no other jets needed to be changed.
The fuel consumption at high speed cruising, (~70 MPH) with the modified jets where down to 1.05 litre per 100km which is ~27 mpg, it doesn't seem so impressive but it is actually about the same as with an untuned engine, so given the fact that the engine now had 200 HP it is quite good.
Information about how to tune Weber carbs can be found in "Four-stroke Performance tuning" by A. Graham Bell and in "Weber carburettors Owners workshop manual" by Haynes books, both books are highly recommended.
Even higher power
Kent V63 cam with stage 2 heads, a Weber 40 DFI carb and a modified distributor is a common combination that will give ~185 BHP at 6100 RPM. For this and all higher state of tune the mechanical fuel pump must be exchanged for an electric one with higher capacity.
Changing the heads for stage 3 or even full race type doesn't give so much more power, but the better breathing make it anyway possible to get a full 200 BHP at 6500 RPM with full race heads, V63 and a Weber 40 DFI carb on a modified standard manifold.
> 200 BHP
In order to get even higher power than this both fuel delivery and the exhaust manifolds must be upgraded, how this is done depends on if the engine should be used for road or competition use.
Choices on the inlet side are either a big twin carb as a Weber 48 IDA on a modified standard inlet manifold, triple Weber DCNF carbs on a special inlet manifold or fuel injection. There are also manifolds available for use with Holley 2 or 4 port carburettors but I can't recommend these combinations compared with any Weber based alternative as they either suffer from bad driveability or bad economy without giving higher power.
A single large carburettor normally give highest peak power, but is a bad choice for street use as low end power will suffer.
The triple Weber combination or individual fuel injection usually give better low RPM performance and better fuel economy.
Triple Weber DCNF carbs, a compression of 10:1 and a Kent V63 cam can reportedly give up to 240BHP with high performance exhaust manifolds, for road use this is probably the practical upper power limit.
For racing there are many possibilities but it is most important to choose a camshaft depending on the use and weight of the car.
Open headers can also give a noticeable power gain with wilder cams but can of course not be used on the street.
Upgrades on the Essex engine
The Essex engine have undergone several modifications during its long life, it seems that the newer engines are much better as improvements have been continuously introduced, these engines are of course the ones that preferably are used for tuning. I have already mentioned the changes to the cylinder heads in 1972 but also other parts have been upgraded as oilpump, cam drive gear and rod bolts:
Oil pump, at least 3 different pumps have been used, early excenter gear type, vane type and late excenter gear type. I know for a fact that the early excenter gear type is not interchangable with the other two, but this pump was only used until late 1968 so then you know the engine is one of the earliest anyway. It is better to change the oil pump for a high-pressure type and use high quality oil. Also check the drive shaft for the oil pump as it has been known for this to break thereby instantly loosing oil pressure. Let the engine be fully warmed up before using full power, this will also increase life of both gearbox and rear drive.
Cam drive gear, The original drive for the camshaft was by a fibre and steel gear combination where the fibre gear is mounted on the camshaft and the steel gear on the crankshaft. It is not unusual that the teeth of the fibre gear are stripped especially if higher revs are used. In 1972 the fibre gear was changed for a gear with steel centre and teeth of nylon but this is only marginally stronger. It is strongly recommended that a steel exchange gear is installed if higher revs than ~6000 rpm are to be used.
Rod bolts, two type exists, early hexagon type and late 12 face "Cosworth" type. The later type are recommended using the correct torque (the torque specification for the earlier type is lower). The con rods and especially the con rod bolts are the parts that are suspected to the highest loads in an engine and it is therefore false economy to re-use suspect big end bolts. As an upgrade ARP Cosworth type con rod bolts are available for the Essex engine and it is easy to install these and it doesn't require any other modification.
How to tigthen cylinder head bolts correctly
The Essex engine can have problems with leaking head gaskets, usually this is due to one of 3 problems:
Overheating leading to warped cylinder heads or,
Use of low quality head gaskets, or
In-correct tightening procedure of the cylinder head bolts.
If the engine have been subjected to severe overheating the cylinder heads can warp and usually start to leak at the outer side of cylinder 2 or 5. The only cure for this is to remove the cylinder head and have it re-faced.
I have heard a lot of stories about low quality head gaskets giving problems in the Essex engine, I have never experienced any problems myself related to head gaskets themselves and i dont think head gasket quality is so important if the correct head bolt tightening procedure is used.
Head bolt tightening
The latest recommended procedure is:
1 Tighten to 20 - 30 lb ft
2 Tighten to 50 - 55 lb ft
3 wait 10 to 20 minutes, tighten to 80 - 90 lb ft
4 Start engine and warm up for 15 minutes, retighten to 80 - 90 lb ft hot
5 Drive the car at least 1000 km and then retigthen to 80 - 90 lb ft hot, (this is really important, usually some of the bolts can be tightened substantially more, last time I was doing this I could tighten some bolts up to one half turn!)
The torque settings has been changed,(it was max
70 lbft earlier)
The above procedure is described in the factory workshop manual for the Essex as used in Granada, but it's doubtful if even the factory workshops really followed this.
I have had problems with water leakage when I didn't used this procedure but never when I done it this way.
There is no need to use new head bolts as they are not of the stretch type, (as used in many newer type of engines).
Screw in rocker studs, originally the rocker studs are just pressed in the cylinder heads and these can creep out if high revs and/or stronger valve springs are used. All seriously tuned heads should have modified threaded studs.
High lift rockers
Some people advocate the use of high lift rockers instead of changing the camshaft, this was more popular say 10 - 20 years ago than now. High lift rockers can be a good modification in a BL Mini or an old VW engine where the camshaft/valve lift ratio only is ~1.25 and where it is difficult to get high valve lift with standard rockers. In these engines it is a quite cheap way to gain some power but in an Essex engine the camshaft/valve lift ratio is already 1.47 and there are marginal gains to be made by using rockers with for instance a 1.6 ratio.
Instead it is possible to get other problems due to the changed valve geometry and modified rockers should ideally be used with cam shafts especially made for this purpose. In any case it is possible to get all the lift needed using standard rockers and a high lift camshaft so it is unnecessary to spend money on high lift rockers.
Roller rockers are today made by for instance Yella Terra in Australia and are said to reduce friction losses in the valve gear and wear in the valve guides. This is true but the gains are marginal at best with a road type camshaft and even many racers don't use roller rockers with high lift racing cam shafts. The price for a set of roller rockers is approximately 3 times the price of camshaft and I believe that this money can be used better elsewhere.
About crankshaft modification
Many people talk about the need for using either Tuftrided or even forged crank shafts in tuned engines and also that it is needed to modify cranks by cross drilling to improve lubrication, but in my opinion these modifications are not needed in an Essex engine used on the street.
If however the engine is used in a circuit race car and spends most of its life at revs of more than 6-7000 rpm, yes than crankshaft modification is probably necessary in order to get good reliability and useful engine life.
If some precautions are taken, these modifications are not really necessary in an engine that is used in a road car with sensible rev limits.
Tuftriding is a process where the crank is immersed in a hot, (570 C) chemical bath composed of Cyanide compounds. Tuftriding creates a tough and very resistant surface zone which improves fatigue resistance, but it does not improve the strength of the crank shaft. It is possible to get about 20 - 60% longer life from a tuftrided crankshaft compared to an untreated one if used in a competition engine.
Forged crank shafts can be much stronger than cast iron ones and are a must for use at very high revs or in high output Turbo engines.
Cross drilling is used in order to improve lubrication on high power, high reving engines, but is usually not necessary on road engines except at very high revs.
If revs are kept below 6500 rpm neither Tuftriding or cross drilling is necessary, it is possible to get higher output by increasing revs to 7000 or even 8000 rpm but overall reliability will suffer and the engine will also have a very narrow power band which make it less useful for street driving anyway. Do however in any case install a rev limiter to ensure that the engine is not overreved.
Ultimate tuning The highest possible power for a normally aspirated Essex with ordinary two valve heads is about 100 Hp/litre, it is possible to achieve this with the original cast iron heads but it is probably safer and easier if the alu heads from Ric Wood are used. On Ric Wood's web-site he describes two engines, one using cast iron heads and the other using his alu heads.
||GP1 310 deg duration, 0.465" lift
||269 BHP at 7000 RPM
||Single Weber 48 IDA
||Triple Weber DCNF
Note that the cast iron heads are equipped with so called GP 1 valves, with the larger valves used in the full race heads it is actually possible to reach the magical 100 HP/litre level but then at almost 8000 rpm which limits both the usefulness and reliability at this tuning level.
Also note that the aluminium heads here are used on a stroked engine of 4-litre capacity, that is why the power reach almost 400 BHP.
Essex dream engine
See here for what is really possible with basically the same engine:
Cosworth modified Ford Essex V6
Back to My TVR
Created on ... January 06, 2001
Updated on ... November 24, 2001
Updated on ... May 31, 2002