If the Ignition system of your M42 engine is getting old and tired and you're looking for replacements, it's worth considering a Coil-On-Plug conversion.

The aim of this mod is to replace the wing-mounted coil packs with individual coils located directly on the spark plugs. That way, you're cutting out the HT leads and providing a stronger, more reliable spark to your engine. Let's get started.

Parts

4 x Coil packs, part no. Bremi 11860 BMW 1 748 017

These are available from M52 or BMW V8 engines

2 x 60mm sections of M6 threaded bar
Various M6 nuts and penny washers
Cable wrap
P-clip
1 custom-made mounting plate, 5mm thick aluminium, as shown below:

Procedure

Before you dismantle anything, remove the existing plate that covers your spark plugs and test-fit your new mounting plate. Make any necessary adjustments.

Once you're satisfied that the plate fits, you need to dismantle your existing coil pack system from the inner wing where it's mounted next to the suspension turret. Number each plug as you remove it, unbolt the coil packs, then feed the wires back around the turret to the firewall.

The next step is to bolt the coil packs to the plate. To bolt them on, put a washer between the bolt and coil pack, coil pack and plate (to protect the coil pack and the plate) and a washer on the other side with a nylock to help secure it:

Plug 1 needs to be modified to allow it to fit in between the rocket cover:

Now mark the plugs according to their number (1,2,3,4) and set about connecting them up to see how they fit. You will find them tight to get them in there as standard, which isn't really suitable in the long term.

For that reason, get some cable wrap to turn the wiring into a loom. Irritatingly coils 1 and 2 are furthest away but have the shortest wires, but it is achievable.