Tuning the Essex V6

AH, THE GOOD OLD ESSEX V6: a throaty rumble and anything from a Granada to a Transit ambulance could be coming around the corner.
But did you know it was originally designed to be both diesel and petrol? That's why i'ts got chambered pistons for the petrol engine - the piston would have been flat for tthe diesel. It's also why it's got large diameter crankshaft bearings, massive
in comparison to modern engines - a bad thing, because the high peripheeral speed of the bearing journals produces excessive heat.
Because the engines are so old, don't rely on the engine number for identification, as the blocks for the 2.5 and the 3-litre are the same and you only have to swap in a 3-litre crank and pistons during a rebuild - you could feasibly end up with 3-litrre pistons and a 2.5-litre crank.

History
The Essex was arguably the first mass-produced V6 in the world, and has since gone on to power, among others, TVR, Reliant and AC sports cars.
It wasn't even designed for a car, but for a van - the Transit.
Called the Essex simply because that's where it was made, it had to be a very versatile engine from the beginning.
Over its history, it has powered everything Ford from Zodiacs to Capris.
As they were made up until 1988 for the Transit, you can still find a relatively young engine, but be careful when buying.
Find and build a good one and you'll discover the joys of torque.
Forget about revs unless you're getting serious and concentrate on low down punch instead.

Block
First up, make sure you know what you've got -2.5 or 3-litre, it doesn't really matter as they're essentially the same, but it will help you know what you're starting with. Providing you're going for a strip down, retap the head-bolt and water pump bolt holes using a plug tap, and make sure the oil drillings are flushed out.
Clean the block before and after you've had any machining work done. Martin, from V6 specialist Car Clinic, reckons you should steer clear of cross-drilling, as it reduces oil flow to the big ends.

Aside from boring, machining work is limited to a bit of chamfering -firstly the bottom of the bores, to stop the piston shaving off the oil on the compression stroke. You can also clean and chamfer the oil filter hole. This gives a better return to the block.
Always make sure you replace the oil pump spindle, due to the corners rounding off. Get one that's been heat treated - it'll be black on the ends. All original Ford items were heat treated.
Only cover your core plugs with a screw plate if it's for racing. Martin does this by tapping three holes around the core plug and filling the cavity between the plate and plug with mastic - this could potentially save an engine in a race situation.
For the ultimate, you could always go for one of Car Clinic's 3.4-litre conversions using genuine Ford OE parts.
That'll set you back a grand for the kit.

Crank, Main Caps and Rods

The Essex, bless its big old crank, suffers from big end overheating and subsequent wear. So, to cut this down as much as possible, Martin recommends grinding the crankshaft to the bottom end of the tolerance, which allows more clearance for oil.
The minimum and maximum tolerances are 2.3761 to 2.3769 inches, so grind to the former.

at either end of the engine. Basically, stick with the standard crankshaft, and if you're going racing, get it tear-dropped and nitro-carburized. When it comes to billet conrods, these are heavier, as the machining doesn't give such an intricate shape as the original Ford forgings. Don't bother. For all 3-litre engines, Martin assures us the standard rod is more than adequate with new bolts. Just make sure they're not Cosworth big end bolts, as they don't exist for this engine - they're actually Lotus twin-cam boltss.
To fit these you have to machine down the caps, so why not just use new originals?
For high performance use, Martin torques them to 40 Ibf.ft instead of 25-30 as standard.

Another thing to check for is gudgeon pin wear. On an Essex, the pin is a press/interference fit in the conrod, so the wear is on the piston and pin, not the rod. This often gets overlooked when rebuilding after a cursory inspection.
As with all cast iron blocks, the main bearing housings were line-bored with the caps in place, but due to the poor quality of many block castings it was often necessary to bore the housings 0.015 inches oversize. Such blocks must be fitted with main bearing caps having a plus 0.015 inch outside diameter. Measure the block before ordering bearings.
It's also been known to find oversize pistons in a supposedly never-been-opened motor. You can see different graded pistons occasionally, because the blocks were sometimes poorly machined.
Unless you're going for new caps and a line bore, the main bear-ing caps have to go back on in their original position, as they're machined on the engine.

Pistons

Martin reckons a particular problem with the Essex is the land in-between the rings breaking up. This is virtually undetectable until you remove the rings - it can then break free. Because most engines have been rebuilt by
now, they may already have over-sized performance pistons - these can be particularly weak. So don't buy rings until you've checked everything.

Standard-type pistons with a 8.9, 9.5 or 9.8:1 compression ratio are still available from Car Clinic, or it can supply new, lighter than standard pistons with a 9.5:1 compression ratio. These are really only needed for racing use, and the engine must be rebalanced after fitment. Car Clinic also likes to do a bit of piston skirt grooving, helping oil retention on the lower piston.

Oil Pump
Beware of fitting a high-pressure oil pump. This might seem like a good idea, hut it's just got a more powerful return and relief spring, which puts undue load on the camshaft auxiliary gear.
People think putting in a high-pressure pump will prolong the life of the big ends. What it does is overload the gear driving the distributor and oil pump, wearing it out. Car Clinic uses a stock pump and pressure for all engines, including racing, concentrating on flow instead.

Ideally, the exhaust valve should be 80 per cent of the inlet's diameter.
If it's too big it can reduce mid-range torque.
All the big-valve stuff came from the '70s where, for Group 1 homologation, they weren't allowed to do any grinding work or flowing.
So they just homologated the two biggest valve sizes they could get in there. Martin reckons for a Fast Road engine, use standard exhaust valves with a 1.7 inch inlet valve. This leaves plenty of metal for the unleaded conversion you're going to want.

The standard compression ratio is 8.9:1, but there's also 9.8:1 in a standard form -useful for an LPG conversion, as it's got an octane rating of 109 RON.

The original rocker studs are pushed in -you only need screw-in rocker studs when you're using double valve springs. The originals can be pinned, but that's as expensive as screw-in anyway. For road cars, leave them alone.

Martin's used to people asking for Reinz head gaskets -they think that's some sort of high-performance gasket, but it's actually the original.
These were good in the '7Os, but you can get better now. There are three types:
one made to the '7Os standard (budget); one made to Ford's contemporary standards; and a competition one.
The latter is only really needed on a true race engine with an 11:1 compression ratio.

Ignition
In Martin's opinion, the world's worst points design belongs to the standard Motorcraft. An inherently weak design.
Upgrade to a Bosch dizzy and points instead, or electronic ignition. but always look for a repairable electronic ignition kit.

One other thing to look out for is that with the distributor in the block, when you use the triple-Weber manifold there's very little clearance on the distributor. Sometimes people file down the base of the distributor, but grind the manifold

Induction
When using the standard carb, make sure you use the W plate, otherwise the end cylinders run weak because petrol isn't being distributed
correctly within the manifold - its all being
dumped into the middle cylinders instead.
The triple Weber manifold is rarely available, so use either 38 DGAS or the Car Clinic produced double manifold for two 38 DGAS carbs. This is the best first step, as most people have these carbs lying amend. Do this and get the car properly set up on a rolling road.

At �300 on an exchange basis - including the linkage - the manifolld is a lot cheaper than a triple-Weber one.
A lot of people use the Weber IDF in Group I racing, but Martin finds a Holley 500 gives better fuel atomisation- lDFs seem to give wet plugs a lot.
For the Capri, they homologated the Weber 40 DF15, quite good for racing but no good on the road, as they don't have a power value and give a very rich partial throttle running - washing your bores out quickly.
Four barrel carbs don't seem to give good results either, a 390 Holley is just too big.
The 500 Holley has a flow rate of 500 cfm at three inches of water pressure drop. Four-barrels like the 390 are tested at 1.5 inches pressure drop, and if the 500 two barrel is tested at the same pressure as the four barrel, it flows at 353 cfm - smaller holes give higher air speed which encourages better fuel atomisation.