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Gearbox Adaptor Plate Template, Part 1 – Dave's Garage Zetec RWD Mk1 Escort Ep 7

Dave's Garage UK Zetec RWD Mk1 Escort – Episode 7 title card: gearbox adaptor plate template, part 1

A Zetec turned north–south for a rear-drive Mk1 needs a rear-drive gearbox, and nothing off the shelf bolts a first-generation (NA) Mazda MX-5 box straight to an ST170 engine. In the seventh video of the Zetec RWD playlist, Dave’s Garage UK starts making his own adaptor plate. He has done this before with an RX-8 box and a bought-in plate, but never with the Mk1 MX-5 box, so it’s an experiment. This first part ends with a finished template, not the final plate.

Video: Dave's Garage on YouTube · watch “Ford Escort MK1 Restoration. DIY Gearbox Adaptor Plate. MX5 NA to ST170. Will it Work? Part 1” on YouTube

What happens in Episode 7

One point matters most (0:00). The whole method hangs on lining up the centre of the crankshaft with the centre of the gearbox input. To give himself a reference, he wraps the end of the crank in insulation tape and taps on a socket with the same outside diameter as the gearbox’s centre spigot.

Measuring and layout (1:08). Corrugated card was too awkward to work with, so he switched to a stiff craft card about 1.5 mm thick and roughly 400 mm square. He marks its centre and a centre line, cuts a 32 mm hole to fit over the end of the crank, and allows a 260 mm width (the measured 250 mm plus some leeway) before cutting anything else.

Marking the engine holes (4:44). He screws 10 mm grub screws into the block. Their pointed ends mark the card when it’s tapped against them, and the marks are opened up with a drill. Awkward holes are marked by pushing a cap-head bolt through from the back of the block. The holes sit at slightly different heights, so marking them directly beats measuring. Only five bolt positions matter on the Zetec, because his custom sump replaces the lower ones. Each hole is labelled F for Ford.

Marking the gearbox side (10:32). The card has a face side for the engine and another for the gearbox, so he is careful never to flip it over. The socket on the crank now earns its keep: the card’s centre hole locates on the gearbox spigot, and a casting mark on top of the bellhousing gives the centre line. With the card clamped in place he marks through the gearbox bolt holes and draws round the outline.

Creating the template (14:23). Back on the engine he traces the block’s outline too, then cuts the card to the combined shape so no metal is removed that either side needs. The card shape is copied onto a 1.2 mm steel offcut left over from the sump work. That’s far too thin to be the real plate (he’s thinking of 6 mm or 10 mm steel for that), but it makes a durable jig. The centre disc stays in until the end so the centre point isn’t lost.

Template test fit (21:03). The bolt holes are deliberately cut oversize. He bolts the plate to the block, adjusts it until the centre is right, then welds nuts to the plate over each bolt, the same trick he used on the oil pickup pipe. The welded nuts are drilled through to 10 mm on the engine side and 12 mm on the gearbox side, making accurate drill guides. A relief is cut for the crank sensor, and the template then lines up on both the Zetec and the Mazda box.

Next steps (22:53). He plans to clamp the template to thicker steel, drill through the guides and possibly use it as a plasma-cutting guide. He’s thinking of high-tensile (10.9 grade) countersunk bolts so the plate sits flush on both faces.

Parts, tools and materials mentioned

  • Mazda MX-5 NA (Mk1) gearbox and the ST170 Zetec engine
  • Insulation tape and a socket matching the gearbox spigot diameter, as a centring aid
  • Stiff craft card (about 400 mm square, 1.5 mm thick) and a craft knife
  • 10 mm grub screws and a cap-head bolt for marking holes
  • 1.2 mm steel offcut for the template, with nuts welded on as drill guides
  • Planned: 6 mm or 10 mm steel plate and 10.9 grade countersunk bolts for the final plate

Lessons for your own Mk1

  • Work from the centre. Get the crank and gearbox input centres perfectly aligned and let everything else follow.
  • Mark holes directly. Pointed grub screws are quicker and more reliable than measuring an uneven bolt pattern.
  • Keep track of which face is which. Flipping the template once would mirror every hole.
  • Make a steel jig first. A thin-steel template with welded-nut drill guides makes the thick final plate far easier to get right.

Mk1 context

An adaptor plate is the part that makes a Zetec and a non-Ford gearbox one unit, and it decides where the gearbox sits in the Mk1’s tunnel. The plate is finished in Part 2, the next video in the series.

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