A few weeks back I took a trip to AK to pick up various shiny parcels and to give my credit card a sharp intake of breath...
The shiny parcels included my side pipes and headers, but also the air inlet pipe, the radiator header tank and the top and bottom radiator pipes.
This meant that I could get on with plumbing in all the radiator hoses.
 |
| Shiny new radiator header tank |
The first job was to swill the header tank out with some water to remove any detritus that remained lurking within. I then filled the tank with water and bunged up the bottom outlet pipe for an hour or so just to check that there were no pinholes in the welds that would leak.
 |
| No leaks from welded joints! |
The header tank is mounted to a cross-member at the front of the chassis. I marked the centreline by measuring between the two radiator top-frames and then marked two lines 50mm on either side to allow for the diameter of the air inlet pipe. I then marked another line midway between the "edge of inlet pipe" line and the radiator top frame and then centred the mounting holes for the header tank on either side of this.
 |
| Centres for mounting holes measured... |
I then centre-punched the holes, drilled out to 6.8mm, and tapped for an M8x1.25 thread. The header tank was then installed using 2No. M8x20mm stainless steel bolts with spring washers.
 |
| Header tank installed |
The radiator top hose was connected up next. AK supply a stainless steel section of pipe which is joined to the radiator and to the engine with some lengths of flexible hose. I had measured the stubs on the engine and the radiator to determine the hose bore needed and had purchased some 35mm bore silicone hose. The AK stainless pipe is actually around 38mm outside diameter, so while the 35mm bore silicone hose could be squeezed onto the stainless pipe, it was a tight fit. To my mind, however, this was the right thing to do; using a larger bore pipe to fit onto the stainless pipe would result in a looser fit onto the radiator and engine stubs and, while the silicone hose might be compressed enough to seal when tightening up the jubilee clips, I think having a tighter fit in the first place presents less risk of leaks.
 |
| AK supplied Top Radiator Pipe... |
 |
| ...installed in place with a short length of silicone hose at each end |
Thinking ahead I angled the tightening screws on the jubilee clips securing the silicone hose at the radiator end so that in future they can be accessed from the side or below; once the body is on, access from the top will be impossible and it's very tempting to just secure these clips with the screws pointing upwards! All the hose clips were tightened to 5Nm torque and rechecked again after 30 minutes or so to allow for any relaxation of the silicone.
Next up was the connection between the header tank and the small pipe on the top of the engine which connects to the water galleries in the cylinder heads, and the header tank overflow pipe. I used some silicone hose with a bore of 6.5mm for both of these. I secured the overflow pipe with a couple of P-clips secured with some M6 button screws to the radiator top frame and the bottom chassis rail.
 |
| Small diameter pipe between header tank and engine |
 |
| Overflow pipe secured using a couple of P-Clips |
The bottom radiator hose was slightly more tricky to fit. The bottom hose has three connections; one to the bottom of the radiator, one to the bottom of the header tank and one to the thermostat housing on the engine. The connection to the radiator bottom outlet was made with a length of 35mm bore silicone hose (same as the top hose). The connection to the header tank was made with a length of 25mm bore silicone hose. I needed to support the bottom stainless pipe roughly level to be able to judge the correct length to cut the required length of hose. I erred on the side of caution and initially made the hose too long and cut it down 10mm at a time until the right length was achieved.
The connection to the engine thermostat was more involved. Other builds I have seen have just used a 90-degree silicone hose bend between the thermostat housing and the vertical section of stainless steel pipe (the angle is slightly more acute than 90 degrees but the silicone hose gives some flexibility to adjust).
I had ordered a 90-degree 35mm bore silicone bend thinking this would suit the purpose. Unfortunately, I discovered two problems. The first was that the leg lengths on my 90-degree bend were too short so when the bend was slid onto the vertical stainless pipe, it didn't reach the thermostat housing. The second problem was that the diameter of the thermostat housing is 42mm and no amount of cajoling would get the 35mm bore hose onto the outlet.
My solution was to order a 38/35mm silicone reducer plus a couple of alloy 35mm hose joiners assembled as shown in the photos below. Ideally, I would have ordered a 40/35mm reducer but Merlin was showing it out of stock for 6-8 weeks and I wasn't prepared to wait that long. You might ask why I didn't just do the whole section in 38mm bore hose, which might have been simpler, but as I had already bought the 35mm 90-degree bend I wasn't too keen on just binning it.
 |
| AK Bottom Radiator Pipe |
 |
| My solution involves a reducer, some joiners and a 90-degree bend... |
 |
| ...all fully assembled |
 |
| As installed on the car |
 |
| The hose from Header Tank to the lower Radiator Pipe |
The last hose to fit was the pipe from the header tank to the top of the radiator. Unfortunately, I hadn't thought this one through fully; the routing of the pipe is quite tight and very dependent on the position of the wash/wipe water tank, which I had not yet ordered. So there was another short delay in the proceedings while I ordered the second tank from AK Sportscars and awaited delivery.
Once it arrived I fitted it in the same manner as the radiator header tank. I could then route the final silicone hose, fix a P-clip in an appropriate spot, and that is another job complete!
 |
| Routing of the final section of radiator hose |
 |
| Not quite relevant to this post - but both bling tanks are in place!! |
