The story of this session started when I was still working on the lights. Stuck for things to do whilst waiting on parts, I read ahead a bit, looking for things to do.
First, there's the horn sounders. For all the other self-build models, there's a couple of threads for these welded to the bar that the steering rack mounts to. On 420's like mine, the engine gets in the way (apparently, not sure why given it's the same engine as the 360, maybe all will become clear when I fit the engine?) so the instructions are, "Drill a hole. Use the spacer that's in the miscellaneous box. Secure with bolt." I had a couple of issues here, starting with the absence of a "miscellaneous box". If I knew the size of the spacer that was needed I could rig something up, but I didn't know and couldn't tell, what with most of the car still being in one box or another, what it was spacing to avoid. So, that was a "phone a friend" job.
I'm still none the wiser where my "miscellaneous box" is or what else might be in it, but Caterham happily posted me a spacer and bolt (and a spare, not sure why I'd ever need two of these...). The diameter of the hole that was needed meant that it was a power tool job. For reasons I'll get to in a moment, I had the Dremel on site today, which made short work of cutting the necessary hole and the sounders were on in about five minutes.
Edited to add: I found the miscellaneous pack on a search for a different part. It was in a box labelled "axle" and, whilst it does contain some plausibly-sized bolts, it does not include the necessary spacer.
Next came the radiator. This was a bit of a puzzle, because the bolts in the back of the radiator point backwards and the fixing points for them on the chassis face sideways. I'm okay with doing a bit of light modification here and there, but don't really fancy welding new steel onto the chassis just yet. Besides, that's one heck of a deviation from the kit as supplied. What was I missing?
Some digging around yielded two unlabelled plates. Offering them up to the chassis confirmed that the holes in the plates were spaced appropriately, and the bite in the size lined up with the anti-roll bar. So these must be adaptors.
I had to "phone a friend" to locate the fixings for them, so asked what was going on here (as, even if I was no longer considering welding anything to anything, this is still quite the deviation ...). It turns out that, at some point, Caterham changed from two sizes of radiator (one for the narrower S3 and one for the wider SV) to shipping all cars with the S3 radiator, but hadn't updated the manual. The plates allow the S3 radiator to fit the SV chassis.
Anyway, mystery solved and fixings located, I could now finally fit the radiator. The drawing shows some bolts in the back of the radiator, that link to "bobbins", that bolt to the [adaptor plates , that bolt to the] chassis. Rather than being integral, the bolts pass through a slotted bracket that's welded to the radiator.
This bracket is a close fit to the radiator. So close, that two of the four bolts are supplied in place, captured with no hope of escape. The other two came in a ziplock bag. "So that's fine, I'll just push them into ... No, that won't work. Maybe if I ... No. Ah." So, I had two bolts that wouldn't come out and two that wouldn't go in. In the absence of better ideas, I fetched the Dremel from home, extended the slots until the bolts could be manoeuvred into place.
And then fitted the horn, whilst the Dremel was on site.
The rest of the installation was uneventful. I loose-fitted all the bolts first, as there was some doubt which side of the chassis brackets the adaptor plates go (there still is, nothing's interfered with it yet, but I've not trial-fitted the nosecone...), where within the slot fitting was optimal for the bolts, and so on. But, not seeing any problems, I tightened everything up and then added the fan. The fan is probably on the right way up as the instructions didn't say for sure, but I think that, were it the other way, then the cable wouldn't reach to (what I presume is, again, bit vague here...) the connector into the wiring loom.