Ford 2.9ltr Cosworth BOA

This engine is a development of the 12 valve 2.9ltr EFi Cologne V6 as found in the later Sierra's and Granada's. The engine was apparently initially developed for motorsport use in the Pro-Sports 3000 single seater series by another tuning company called Brian Hart Ltd. Cosworth it turns out bought the rights to this company in 1987 thus inheriting the engine development program. The engine was then detuned and domesticated before being slotted into top of the range mk3 Granadas in an attempt to take on the BMW 5 series. The reason behind the de-tuning of the engine was down to traction problems. The engine was never fitted to any other model and was always attached to a modified electronically controlled version of the Granada V6 automatic gearbox. Because of this, the engine is set up to favour this transmission and it is said that there is a noticeable increase in power and torque above 3,000 revs.


Power - 195bhp @ 5750rpm
Torque - 191lb.ft @ 4500rpm

Although based on the 12valve 2.9ltr Cologne V6 there are no interchangeable parts with the exception of the main crankshaft bearings (not including the thrust bearing). Even the block casting is different, apart from the obvious lack of push-rod openings the Cosworth block features additional and beefed up internal webbings to increase rigidity.

It is not without its own problems though. These engines are prone to wearing out their timing chain 'blade tensioners'. These are made from nylon and wear over time, often ending their careers by eventually snapping in half. All the debris from the wearing forms a sludge which then goes on to clog up oilways causing oil starvation. Replacement parts are available, though not from Ford, so a web hunt is required. Parts aren't particularly cheap either to replace the tensioners including all required gaskets etc... Also, be careful if you ever need to remove the rocker covers as the rubber seals are bonded to the rocker covers and if you damage them beyond re-use (quite likely if they've never been off since the engine was assembled which they probably haven't) you'll have a new headache to deal with.

This Cosworth engine, named the BOA, was further developed itself later on to create the BOB. This newer engine featured among other things a re-designed plenum, revised cam profiles, a different timing chain arrangement and a variable resonance induction system. It also featured a new engine management system which incorporated the 'PATS' system which is a security/immobiliser system requiring the correct encoded ignition key to be used to disable it. This makes the fitment of this particular engine a little more complicated if you are using it's original engine management system and so the BOA has generally been the preferred choice for ease of conversion. I suspect the issue is more to do with fault finding. If your BOA conversion won't start at least you know it isn't the immobiliser!

Preparing, Fitting and Wiring your Cosworth BOA V6

I have broken up the necessary work into sections as shown below. This particular conversion was carried out on a 1982 Ford Cortina so some of this guide is tailored to that but most of it is relevant whatever you are fitting the engine to.


What's Required and Why

Your basic shopping list


Parts Preperation

Preparing the engine prior to fitment.
What to add and what to remove.


Engine Installation

Whatever car you are fitting this to you will want to remove the bonnet, radiator and grill to give best access.

For the Cortina you will also need to remove the heater unit as the LH cylinder will foul on it, more on that later. Also watch for the steering column coupling getting close to the RH exhaust manifold.
If you are using a type 9 gearbox and have not removed your prop-shaft don't forget to guide it into the gearbox as it approaches it's final position.


Fuel System

As with all EFI engines this engine requires a good consistent pressurised fuel supply. On my installation I used an external pump and accumulator as found on Bosch K-Jetronic fuelled cars but this wasn't very satisfactory. A much better solution is to fit an in-tank high pressure pump as described in the link.


Cooling system

Keeping its cool.


Induction and Exhaust

Its sucks and blows...


This is one of the more challenging bits of any engine conversion and gives some people the fear.
Hopefully these bits of information will clear most if not all of that up.


ECU Pin-Out List

One of the holy grails of any engine conversion.


Wiring Loom

You might think the ECU Pin-Out list is all you need, but you would be very wrong. There are a few bits within the wiring loom itself that took a bit of detective work.


Rev Counter

This section is very much geared to my own conversion on the Cortina but it may help give ideas for your own particular build.

Live Action Video

Recorded on shaky old technology with appalling sound reproduction...

Any adverts are youtubes' doing and beyond my control. I certainly don't see any revenue from them!


The contents of this website are purely a reflection of my own experiences and knowledge gained whilst working on my various projects. Anything you do based on what you have read here is done so entirely at your own risk.
Personally I wouldn't trust someone like me with a lawn mower! You have been warned! Flapper-bat!

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