After installing the wiring harness and installing the coolant re-route, it was now time to install the MK Indy bulkhead and mount the brake pots and coolant header tank.
Bulkhead
I have the older style GRP MK Indy bulkhead, as the kit is from 2022. The latest kits use an aluminium bulkhead instead, but the approach will be very similar. The first thing I had to do was to cut back the front edge of the bulkhead to fit around the coolant re-route that sticks out the back of the engine. This was a simple mark-up with masking tape and cut to shape with a saw. Then I ran a piece of U-channel rubber on the front cut edge to finish it off cleanly.
Then, to make the bulkhead fit flush on the chassis rails with the bodywork, I added some 3mm rubber to the top of the chassis rails. This will also stop any vibrations, a thing I really want to avoid with this car. I also added some M4 rivnuts to the top of the chassis rails. This fixes the front edge of the bulkhead down onto the chassis.
The next element was to mark out where the holes should go on the MK Indy bulkhead. I chose 9 holes in total at roughly 100mm apart. I then drilled through these points in the bulkhead in situ, so it also went through into the scuttle with a 4mm drill bit. This marked the scuttle where I needed to open up the holes and fit a rivnut. I then used a 6mm hole to open up the scuttle holes and fitted M4 rivnuts. Once all of the rivnuts were fitted, I added some Gorilla epoxy resin to the back side of the rivnut. This is to stop any chance of the rivnuts spinning when trying to undo the bulkhead.
To stop further vibrations and to finish it off, I glued some thin rubber trim/ tape to the back of the bulkhead edge. This presses up against the scuttle and provides a nice seal.
Brake Pots
Next was adding the brake pots to the MK Indy bulkhead. I have the older, larger style brake pots, as MK has since adopted the same cylinders as the clutch for the brake pots as well, with a built-in cylinder. I didn’t want mine mounted directly to the master cylinders due to 2 reasons:
- The brake pots would be difficult to get to due to the coolant re-route I have going around the top rail of the chassis.
- The brake pots I have don’t actually fit without bodging them with PTFE tape. The tapers are wrong to mate correctly, and I’m not going to start bodging anything to do with the brakes!
So my approach is to mount them on the bulkhead and get custom brake hoses made to go from the brake pot to the master cylinder.
I used HEL Performance to get them custom-made using the following 2x designs
600mm Line – HEL configurator
The quality of these lines is excellent, and they arrived promptly and fitted perfectly. I would highly recommend using HEL Performance for any brake hoses. Their service and quality is excellent and at a good price.
Fluid Level Sensors
I added the brake fluid level sensors as per the manual. This drills a hole in the centre of the cap big enough for the sensor to bolt through. Once I had fixed them in place, I used a bit of Gorilla Epoxy resin to make sure they were sealed.
I then drilled a small 1mm hole on one side of the cap to replicate the previous breather hole. This was originally directly in the centre of the cap where the level sensor now is.
Brake Pot Mounting Bracket
With the kit a bought a brake pot mounting bracket as I knew I wanted to mount the pots higher up. I used a small 2mm aluminium plate on the back of the bulkhead to spread the load of the mounting bracket. Then drilled and bolted the bracket to the bulkhead with stainless bolts.
I also made the brake level pots cables fit to the wiring harness with the 2-pin Econoseal connectors I had. This means I can easily remove them later if needed.
Coolant Header Tank
I then fitted to the MK Indy bulkhead the OBP coolant header tank that was with the kit. I used a similar approach to the brake pots. Where I made a 2mm aluminium plate for the back of the bulkhead to bolt through to provide strength. Then a short silicon hose to join the header tank to the coolant system near the back of the engine.
Battery
The final element for the MK Indy bulkhead was the fitting of the battery to the tray. For this, I had the standard old-style GRP battery tray and lid. The old MX5 battery fitted perfectly into the allocated battery space.
I bought some M8 stainless threaded rod, used an aluminium plate I made underneath for strength and then used some leftover fuel hose to cover the thread. I created a couple of cutouts in the lid for the battery terminals and cables. Then used u-trim on the edge for protection and a piece of rubber on the underside of the lid to keep things secure. The final piece was to cover the underside fixings with a rubber matting for IVA to stop any protrusions into the footwell. I’m pleased with the result.
Summary
I am very happy with the overall bulkhead setup, which was finished off by adding the MK Indy VIN plate and brake fluid warning sticker that also came with the kit.
Summary of Build Costs and Hours
Here is a summary of the costs and person hours (total number of hours for every person that has helped) for the build so far. This should hopefully help others with the planning of their builds, by providing cost and time actually incurred for this build. A more detailed breakdown of all the costs and hours worked on the build to date can be viewed here.
| Person Hours Worked This Post | |
|---|---|
| Fit Bulkhead, Coolant Tank, Brake Pots and Battery | 6 hrs |
| Car Build Costs This Post | |
|---|---|
| 2x HEL Performance Custom Brake Hoses from Brake Pots | £63 |
| M8 Threaded Rod Stainless 300m 4 Pack | £11 |
| Rubber Strip 3mmx25mmx3M Self Adhesive for Chassis Rails | £14 |
| Silicone Tubing 8mm ID 10mm OD 1M for Header Breather | £7 |
| Gorilla Epoxy 25ml | £7 |
| Battery Clamps Solid Brass Qty 2 | £5 |
| Battery Terminal Covers -ve and +ve | £8 |
| 10M Black Rubber U Channel Trim 10mm x 4mm | £7 |
| Neoprene Rubber Roll 15mm x 1.5mm x 3M for Bulkhead and Clocks | £7 |
| M4 x 20mm Black Flange Button Head Screws | £6 |
| Banjo Bolts 7/16" Stainless Qty 2 | £10 |
| Totals | This Post | To Date | All Posts |
|---|---|---|---|
| Person Hours Worked | 6 hrs | 492 hrs | 500 hrs |
| Car Build | £145 | £13,715 | £13,956 |
| Tools / Consumables | £0 | £470 | £470 |
| Total Cost | £145 | £14,185 | £14,426 |