Day 12: Engine running, rear lights, tidy wiring, prep front wings

I’d been away all week and hadn’t managed to get the engine running before I left because of the problems recording oil pressure. Whilst I was away Derek had sent me a new oil pressure sender as a first attempt at trouble shooting my gauge not showing any pressure

O/P Sender swap

A simple job. I applied PTFE tape to the thread, placed a drip tray underneath, and removed one sender to replace as fast as possible with the new one. I estimate I lost a thimble full of oil in the process, so nothing to worry about.

Of course I immediately tried turning the engine over on the starter motor again to see if it was working, but still nothing.

So in the end I decided it was time to start the car properly. Just for reference, what I had been doing prior to adding any fuel into the car was disconnecting the crank sensor connector block (front RHS engine) to avoid a spark.

I had previously filled with fuel so I also disconnected the Inertia Switch connector, as this shuts off the fuel pump and stops fuel flowing. It’s good that other home builders know what these two connectors do. I favour removing both, as a belt and braces approach. There is no need for fuel flow or spark when cranking for oil pressure.

Starting the engine

There are no two ways about it, this is nerve wracking, more so in my case that I never saw any oil pressure. If you have a dry sump 420R, then seeing oil return and flow around the system means you do have pressure, so don’t panic.

It took 4 or 5 attempts to start the car once I had reconnected the inertia switch and crank position sensor. This is fairly normal, and it would catch and then die almost immediately. Primarily its just getting fuel into the system.

I should have realised when I was adjusting my throttle cable for 0 to 100% open/closed that actually without any air coming in on closed, it was never going to run. I adjusted the screw under the throttle spring enough for the car to stay running once I had let go of the throttle. Its probably running a little fast on idle, but its running, all by itself.

I noticed that my coolant level was very low, and stopped the car to investigate. Turns out that I had a very small coolant leak at the temperature sender, as I hadn’t tightened this up enough. Once fixed, I topped up and started the car again.

I was checking that the engine was running on all cylinders and therefore could also see that the primaries were changing colour at the same rate.

I was also checking for water temperature on the gauge and I aimed to leave it running until the thermostat kicked in, cooled the water and switched off again.

All of this worked beautifully, with one small exception. The damn water temperature gauge is not recording any temp in the same way to O/P gauge records no pressure.

Im going to have a word wit hDerek on Monday, but someone on FaceBook has mentioned that it could be that the gauges themselves are not earthing correctly. I will ask Derek what I am to look for and fiddle with here.

Here is the video of the car running up to temperature and all sounding well. Another magic moment on the journey to completion!

Rear lighting

This job is made all the easier because Caterham pre-drill the large central hole to feed the wires through and the inner lower corner hole for mounting the light block.

The only real challenge is finding a level. My floor was level, but the car was sitting slightly out of level on its axle stands, so I adjusted that, checked again, then felt confident that using a spirit level along the top of the light blocks on either side would get them horizontal.

I simply held each light level whilst drilling with the other hand. I didn’t feel the urge to mark holes before hand, or use masking tape, I just went for it. The holes in the block and the rubber act as a guide and fibreglass is simple to drill through, just follow the guide, removing the bulbs before you go for it!

You have to feed all of the cables through inboard of the body after connecting, and use this inner hole for covering with the grommet attached.

I then attached the number plate light, pulled through excess cable and removed the excess, whilst using my wire strippers to provide me with enough wire to crimp a bullet connector on to the end. I found one in my tool box, so straightforward. Since then I have found a little bag from Caterham with some connectors in it, but I’m happy using my own bullet. You have to remove the little brass sleeves that cover the hoop for connecting the bullet too inside the light. I also filed off a little powder coat on the bracket so that the screw and nuts that attach the light to the bracket are earthed.

I finished off the rear end with the 420R decal, and the end result can be seen in the picture below. I tested all lights and everything works!


Tidying cables

I decided that I would spend the next hour or so just tidying up after myself, and this meant cable ties. Specifically I tidied up the handbrake cables, the speed sensor cable (hopefully leaving enough slack), and the Lambda sensor cable.

In the kit you receive 4 small black cable tie blocks with a hole in the middle of them. Derek informed me that these are to be used by riveting them to the chassis under the drivers side foot box, so that’s what I did.

It was a bit of a pain because of limited access and trying to use a rivet gun whilst lying on the floor is harder work than normal.


The other cables were easier and mine are routed like this, but Caterham may still wish to adjust these at PBC:

Preparing front wings

I then moved on to the front wings and prepped the wing stays first. After fiddling with BigHead mounts (to cable tie the wings in place), I decided that these would slightly raise the height of the wings and I didn’t like that look as much.

So I have decided to simply stick them using Sikaflex. But this means that to do this properly you need to remove the powder coat from the wing stay where it will be glued. I did this easily with 120 grade sand paper, right down to the metal.

And then you have to drill a 4mm hole to the underside of the forward wing stay, as the earth for the side repeater will be attached by rivet here. I had a think about this and decided that drilling a round tube is hard enough, I would drill from above and go through the top and bottom material of the tube. It seemed far easier than drilling from underneath and the wing stay is covered by the wing anyway.


I then prepped the wings by adding IVA rubber all around each edge, only to find that I have not been supplied with enough. I have completed one wing, but I’m about 3 cm short on the second, which is damn annoying. I’m sure Derek won’t mind providing me with another length.

And then I went to B&Q to hunt down a drill bit suitable for drilling out the centre of the 3 holes on each wing to attach the indicator repeaters.

After B&Q advice, I went with a 13mm steel drill bit, which cost me around £15. The guide suggests cutting a hole of 15mm, but with fibre glass disintegrating slightly and the back nodule of the indicator smaller than 15mm, I went with 13mm.

IMG_1941It worked perfectly, copious amounts of masking tape used, and I went up from 6.5mm through 8mm to the final 13mm bit. The trick is to get the drill bit spinning fast and then go for it!

I then placed the wings on the wing stays and chickened out of fixing them because I was unsure of how far forward or backwards they should be placed. Also, as you can see from a dry run photo below, the LHS (right side in photo) wing stay is bent a little upwards so the wing edge doesn’t run horizontal to the ground.


So I gave up work for the day, tidied the garage, spent time with the kids in the back garden, and fell asleep to the monotony of the Hungarian Grand Prix….

There’s always another day!

Day 11: Seats, fluids and Oil Pressure


This was really straightforward, and maybe it’s because there is a little bit more space in a SV chassis to wiggle the runners around.

The weird thing with my kit is that I only had one set of runners. The other set is actually two aluminium box section tubes that you bolt onto the seat and then they fix into the floor.

I did what I thought would be best to get it through the IVA and put the runners under the drivers side as I guess this has to be adjustable to pass.

In reality I think that the fixed seat method may be better for me as I am so tall and I think it takes the seat a little lower and slightly further back.

I may still have problems though. In my old K Series I got very used to sitting lower on a bag seat. I had S-Type seats and removed the seat squab, kept the rear bit, and sat on the bag. An ugly looking solution but the perfect driving position for me.

I was hoping that the composite Tillett would get me low enough and far enough back but I fear I may have to go for a full bag option post IVA.

Either way the drivers side with the seat runners was a little more fiddly because of a really badly designed seat runner adjustment handle. It is supposed to slot under the lowered floor cross member. It does, but you can’t move the seat fully forward because it fouls. Not really a problem for me, as it’s only ever going to be fully back. On this side the bolts drop down through the floor.

On the passenger side the bolts pass up into the threaded holes on the underside of the fixed bracket. Looking at these fixed runners I think alternatives could be fabricated that drops the seat a little lower. Or maybe they could be dropped altogether and then I just use a stack of Tillett black spacers. Not sure whether this would spread the load on the fairly thin floor though. Questions to ask the guys at BookaTrack.

Oil Pressure theory

There comes a point when even I have to stop chickening out of starting the engine. Today was this time. But it didn’t quite work as planned.

On advise I decided to removed the crank position sender at the front of the engine as a way of avoiding a spark. In fact I went one further than that and didn’t put any fuel in.

The objective is to crank the engine over on the starter motor until oil pressure is registered on the gauge.

But before that point we had to fill and bleed both the clutch and brake fluid.

Clutch fill and bleed

Really simple job, pour brake fluid provided into the clutch reservoir, use a bit of flexible tube over the bleed nipple, then into a small container so that fluid covers the tube.

Then undo the bleed nipple and pump the clutch until fluid minus air bubbles is drawn up and out towards the container. A quick tighten of the bleed nipple later and we had a good feeling clutch pedal and we’re playing around changing up and down the gearbox.

Brake fill and bleed

I’ve done this plenty of times over the last 5 years on my old Caterham as I was never quite happy with the feel of the brake pedal, it was always a bit soft.

So this time around I selected the upgraded brakes which comes with an upgraded brake master cylinder plus twin pot callipers.

The only difference this makes is that there are 2 bleed nipples on each side at the front, so the inners need to be bled before the outers.

I used an EasyBleed kit and filled starting from rear LHS, then going to rear RHS, followed by front LHS and finishing up with front RHS, in effect rotating around the car from the furthest point from the master cylinder.

I had a little bit of a leak in the fronts where I obviously hadn’t quite tightened up the connectors inside the body skin. Sorted that, wiped down and squirted ACF50 to dilute and rinse down the inner skin.

I also had the connector to the inner calliper leak a little, and so I nipped that up an checked the other 3 (inners and outers) on the fronts, seeing as these came pre built.

Anyway, to cut a long story short I’ve bled twice since and I’m still not happy. The pedal starts to firm, and then after a few seconds pause goes soft again.

I will have a go using the old fashioned brake pedal pump method and bash the callipers with a spanner to try and release trapped air.

So I stopped faffing with that because I was still, as I said earlier, putting off the inevitable.

Engine oil fill

I made a decision a few weeks ago to get my engine run in professionally at Northampton Motorsport. Basically they put it on their rolling road and during a 2 hour cycle bed the piston rings in properly and leave me with a car I can thrash around a race track without having to mess around for 500-600 miles myself. Seems smart to me, but I know there are lots of differing opinions on this. Either way, to go through this process properly I needed to buy special running in Mineral oil. I bought 10 litres of Millers CRO 10w-40 and this is what I used to fill the car with.

The assembly guide tells us to dump 5 litres in the top of the engine, but seeing as it’s a dry sump system I checked with a few others on this point. Derek, another 420R self-builder had been through a bit of a painful process here, and was eventually told to put 3 litres in the top of the engine and 4 in the dry sump tank. I double checked with ‘Caterham’ Derek and he confirmed this. So that’s what I did.

(Not) Getting oil pressure

So with the crank sensor removed and no fuel in the tank, and oil in roughly the right places I fished out the key, switched in the ignition and pressed the starter button. I held it down for about 30 secs and registered no oil pressure.

Craig then took the cap off the oil tank and witnessed gushing oil re entering the tank from the top inlet, in effect back from the engine. So we had oil flowing and therefore should have been seeing pressure on the gauge.

I kept trying in 20 second bursts but then the battery started fading so I stopped, charged it for an hour on my Optimate trickle charger and then tried again. And again, and again. Still nothing. So the concensus is that I have oil pressure but either a dodgy oil sender or a dodgy gauge. My money is on the sender. Seeing as the gauge sweeps around on ignition as the others do, so it has power.

I was doing all of this on Sunday, so with no Derek to check I didn’t try and start the car properly. I needed to hear his opinion. So I left it until Monday first thing. He agrees with the assessment we made and is sending me a replacement sender and a gauge.

Unfortunately I’m now away in the US with work for the week, so can’t get the engine started until next weekend.

Derek seems to think that we should just start the engine seeing as we have oil flowing around the system. Then see what happens. I’m thinking about this approach and undecided. I may still swap out the sender first, as I have this urge to see the gauge function properly.

potentially faulty sender

So that’s it for now. I have to get the engine going, and it’s all I can think about at the moment.

After that it’s the rear lights, front arches, roof, so fun with poppers again, the tonneau, the doors and mirrors and I think I’m finished. Which means that I potentially will be done 13 days in. My average build day is around the 6 – 7 hour mark based on recorded 60 second interval photos from my go pro. Which works out at an 85 hour build. But my cup is always half full, so we will see, I may need a few more days taking me close to 100 hours of effort. I will report more accurately at the very end!

Day 10: Wings, Air box, Boot cover & Harnesses

Realisation dawned towards the end of day 10 that I was in the 80/20 rule mode. 80% of effort will likely be the final 20% of the build. This thought occurred just after the second time I bashed my thumb with a hammer trying to peen the back of a boot cover fastener with the really annoying hammer and anvil took provided. But the day started with the rear wings, so back to there.

Rear Wings

This was an in the house on carpet kind of job. Its much easier than it looks, was something I was worried about beforehand but went very smoothly. Mainly because I am now really into riveting!

I used masking tape to tape the thin rubber edging strip around 3 sides of each carbon fibre stone guard, snipping triangles out of the corner areas to make the strip follow around the curves. I then stuck the whole thing to the wing using more tape and drilled out through the fine glass wing via the predrilled holes in the guards. 5 minutes of riveting later and I then peeled off the tape showing on the front face. The rest of the tape I left behind, hidden between the guard and the wing. Then repeated the other side.

Once the guards were fitted I attached them to the car. Or I tried, before I remembered that I had to cut out a chunk of wheel arch to ensure that it doesn’t snag on the radius arms. It’s surprising how much you need to cut out to make it fit. I used a hacksaw and a file to smooth the rough edges away.


I had no problem fitting the RHS arch, but one of the pre-installed rivnuts on the LHS side skin was not inserted correctly, sort of squashed inside and when screwing a bolt in it started rotating. So I had to drill out, which unfortunately kicked off a chain of events which made the rivnut rotate and grind down a bit of the skin. Once removed, I inserted a slightly larger rivnut and sorted the problem. Thanks to Craig here for helping me calm down during this painful exercise!

Air Box

This was one of the smallest jobs to do, but turned into one of the most painful. As previously mentioned, Caterham had supplied my chassis with the 3 rivnut holes drilled in the wrong places.

In the end, Derek provided me with a template to ensure I could mark the correct locations for the holes, a bunch of rivnuts and 3 new air box bobbins. Apparently I had been supplied with the wrong type of these too. The ones in my kit were long, the ones I needed were short. I found this out randomly during a conversation with him!

short bobbin (top) for SV 420R, long one for S3
I’m still not happy with the fact that I have extra holes drilled, and I will take this up at the post build check. Meanwhile, a job I should have completed with my eyes closed a week or so back was eventually completed after I borrowed Craig’s rivnut gun.

Boot Cover & Harnesses

My next objective was to get the seat in. But in sequencing akin to the “thigh bone connected to the knee bone” I needed to insert the roof strakes (for holding up the hood) before I could attach the boot cover, before I could attach the harnesses, before I could attach the seats!

The roof strakes were simple, but the picture in the assembly guide is for an S3, and the SV ones are laid out differently and shaped differently. But its fairly obvious what to do!

They need a self-tapping screw driving into a hole drilled into the boot top chassis member, and this needs to be done so that the first strake is 420 mm from the top of the boot top chassis.

Before you place the boot cover in position the metal strip inside the seam at the leading edge (seat back edge) has to be removed. Simply unpick the thread at one end, slide the bar out and then super glue the opened end back together. 

Then the cover is placed in position and I used a 5mm (only one I had, could have done with being 10mm diameter) leather cutting punch to cut out the 4 holes directly above the pre-drilled holes in the chassis for the harness fixings. I then used the same tool to poke through the flap of the rear carpet that was covering the same holes. 

I actually needed to make these holes bigger and used a Stanley knife blade to do so. I took my time to make neat larger holes, big enough for the harness bolts to just go through. In retrospect I could have been a little more aggressive here, as the holes are covered with the seat belt mounts, so no need to be super neat. 
And then I placed the boot cover in place and bolted the harnesses in. The harness bolts, mount spacers and washers were in the harness packs by the way. Knowing that will save you the 10 minutes of idiotic grovelling though every bag looking for them!

The order of the fixings is in the manual and you don’t seem to need to use the cardboard washers at all. The crush washer goes between the spacer and the belt itself. The regular washer goes directly between the bolt head and the belt.  I had also heard that other folks boot covers twisted a little when tightening the bolts to their final torque. So I squirted rubber lubricant around under each bolt to mitigate against this. It worked a treat. 

The important thing to note is that you have to think about the boot cover fitting around the roll bar and having enough material left to pull tight around the edge where the poppers go. With this in mind make sure that you don’t line the leading edge of the boot cover with the edge of the bulk head. It won’t give you quite enough wiggle room. Move it back around 5-10mm so it appears ‘stepped’ under the harness bolts. 

Once all of the harnesses were in place, Craig and I got to work on the poppers. Starting from rear central one, then working out and around keeping it all really taught. Easier with 2 people, but viable with one. 

Two super important tricks here. One, use masking tape under the boot lid and press it down when really tight over the existing make popper base on the chassis. It creates a perfect circlular indentation. I then used my paint pen to blob the centre point of this. 

Second important trick is to use a fabric punch. I didn’t have the right equipment here, but Andrew, my next door neighbour did. I selected the right sized hole and then one squeeze later a perfect little hole appeared. Simple. 

Then the pain of using the Duradot tool. It’s awkward because you need a sturdy base to wallop it on. Craig held a piece of wood in place against the bulk head and then I used a hammer to complete the job. Others have better hammering skills than I. My left thumb is still throbbing two days later!

But it was worth it, because the finished boot cover fits really well and is tight over the poppers. A very satisfying job to complete, and the first time I’ve ever fitted poppers. Not rocket science but still, every day is a school day!




Day 9: Electrics, carpets, temp sender

The start of lots of smaller jobs

So, as I mentioned yesterday, I am now at a stage where all of the big mechanical jobs are over. To the uninitiated, it now looks like I am close to completing the car, but the next phase of the build will take a while.

I still have carpeting, interior including seats, wings, boot, boot strakes, doors, rear lights and number plate light, weather equipment (tonneau, hood, wipers).

Its still going to take a while! But today is all mainly about carpets, testing and a little rework on the water temperature sensor.

Electrics (testing)

First thing this morning I connected the battery, found the key from its cool welcome box and turned the ignition on. This is quite a big moment. I haven’t got to the stage where I have fired up the engine yet, I am waiting for some specific competition running in oil and also need to rework the water temperature sender before I fill with coolant.

However, I tested all of the electrics and everything worked! All dash lights, headlights and front indicators working, horn, dash illumination, windscreen wiper motor, reversing light and fog are working.

And here is a shot of the mileage, which is rather cool, and some working lights:

Temperature sensor rework

A minor frustration that Dan Smith and Simon Calvert both identified before I got to the problem proper was that the build guide makes no mention of the fact that you have to earth the temp sender via the black and yellow cable shown below. I mentioned this in my day 7 post, and showed a picture of my sender fitted as I thought best. I actually used the screw thread on the bottom of the sender to locate into the plastic water pipe carrier attached to the rear of the engine. What you actually have to do is turn it upside down and then route it close enough to both of the connectors as per the picture below. For me this meant that Derek had to send a new J hose and the new earthing bracket and nut as shown. These parts are not provided, so it was impossible to see this coming.


Rear Bulk head carpet

The first thing I did was wipe down the inside of the car with a damp cloth and some surface cleaner. Then a dry fit of the rear bulk head carpet showed me that I needed to make two small cuts so that it would sit well over the rear tunnel. I then used some contact adhesive spray that had been recommended by others. I sprayed over both the back of the carpet and onto the bulkhead itself. The nozzle has three settings and it’s accurate to spray and avoid overspray. Where I had the odd wild spray moment later with boot carpet fitting, overspray can be cleared off with a cloth and some WD40.


The photo above shows the carpet stuck down and the start of the next stage, which is riveting the tunnel top plate down. I also chose not to apply glue to the rear carpet here in the sections lower than the tunnel. There is no need as the seats back into this, the carpet doesn’t flap around, and if I ever needed to remove the carpet, it would give you the ability to pull up from the bottom. The carpet covers the holes for the access to the bolts of the rear suspension mounts.

Tunnel top plate & rivets

The tunnel top plate is very easy, just a bunch of rivets to fix. I invested in a ratchet rivet gun which is a lot less effort than a basic one. Each rivet needs around 2-3 pumps on the handles, but these are almost finger tip effort compared to a standard “feel the strain and pain” ones in my opinion.

Knee trims

Well this is a painful job. I knew it was going to be, but after reading lots of other blogs, I still step into each job in positive mental attitude mode assuming that the others before me obviously didn’t do something quite right and I will prove how easy it actually is.

Well, quite simply, its a total pain in the backside. In fact lets me more clear. The LHS knee trim panel is impossible. The RHS one went in relatively easy, say 5 minutes of alignment and then tapping screws started to go in. The advice from others is that once you have lined up one hole at either end, stick a temporary rivet in this hole and then you can rotate the plate to get it aligned and jam a second rivet temporarily in this hole. This worked a treat on the RHS. After an hour of fiddling on the LHS I gave up and aligned it my way. Now its important to think about the fuse box cover and 12V socket carrier. This piece basically attaches to the LHS knee trim panel, so any non-standard fixing has an impact on alignment of this. I worked through and got everything floating and nicely aligned, got out my paint pen and marked up through the inner body panel holes onto the knee plate.

When I extracted the plate to look at where I thought the holes should be drilled, I was around 10 mm above the existing pre-drilled holes, and these were parallel to my paint dots.

So I had another go at trying to get the knee panel properly in place without DIY holes and spent another 30 mins cursing and not getting alignment. A cup of tea later and I wimped out, drilled new holes, and within 10 minutes had the knee trim panel in pride of place, with rubber trim all lined up underneath and the 7 self-tappers screwed in as below.


Carbon Side sills

The next job was to fit the carbon side sills, in effect a push fit over the edge of the body panel where your arms would rest if you didn’t have the doors or door arm rests on.

The assembly guide doesn’t quite say whether these should be positioned fully back towards the rear wheel arch, or fully forward towards the dash. They could do with being a bit longer to fit the complete width of the gap. In the end, I looked at how they would be attached (through pre-drilled holes in the inner skin and decided on a middle/middle approach.


The assembly guide provides a good image of the layout here, because the end result is that you have to trap rubber trim between the skin and the carbon sill. You need to drill through the skin holes to then drill through the carbon. Then fit the rubber trim and drill again to make sure that the rubber is pierced in exactly the right place, whilst making sure that the trim is lined up nicely.

Then its a case of riveting all of this together. If you have arm rests on your doors, then you need to leave 4 holes un-riveted for the escutcheon fastener (the silver item in the photo). I have temporality slotted it in place as a reminder. This will be aligned later and drilled out through a few of these holes, then riveted in place. You just cant do it until the doors are attached to the windscreen surround and then lined up properly with the other end of the escutcheon fastener.

Tunnel TopIMG_1822

The tunnel top un-bagging from its box was rather upsetting. Its in nearly perfect condition, but nearly is not good enough. Its been damaged at some point, possibly in transit. I inserted it temporarily, as you can see from the image above, but the rear face that rests against the bulkhead carpet has been bashed up. Underneath the top surface, its actually a very tough metal base and is simply too hard to band back into shape. And even if I could, there is a small “nick” out of the surface material in the same area. I contacted Derek and sent photos through to his email, and as luck would have it, Caterham have some in stock so I will receive a replacement shortly.

Fitting this was simple however. I didn’t un-peel the backing tape on the sticky pad near the gear stick as I will do this when the new tunnel top arrives. What you have to do is lift the handbrake up to its highest setting and then simply insert over. I screwed the gear knob on for a more finished look whilst I’m waiting. Its starting to look fab inside the car!

Floor carpets

I received two large almost rectangular shaped pieces of carpet, and these are for the floor underneath the seat. These pieces are shaped to fit a car without lowered floors, so I placed them inside the car and they were too big. I folded and pinched marks on the oversized carpet along one side to find the line for trimming, then used my Stanley knife against a long rule to cut the carpets down. Some contact adhesive was then applied and the carpets stuck into place.

Boot carpet

I then moved backwards to the boot area, where you receive lots of little shaped pieces of carpet, and they are to be stuck all around the inner skin of the boot and against the rear bulkhead. They all fit beautifully and again I got my contact adhesive spray out for this – I’m on my second can of the stuff!

I may have made a slight mistake simply by following the build sequence and assembly guide here. I didn’t think it through but a piece of carpet on each side covers 3 holes that are used (along with others) to attach the rear wheel arches.

Ideally, I think perhaps these should be fitted before the carpet is stuck over the nut and washer when the arches go in. However, the carpet would then not fit beautifully, and be really lumpy over the bolt ends and nuts. Maybe I have done it OK, and I poke the screw from the outside arch through the carpet, and terminate with a washer and nut that remain visible inside the boot. It would make more sense and make it easy to replace rear wings from an access perspective. Either way, thats what I’m doing, because the carpet is stuck fast!

Wheels on and car off its axle stands!

Final act of the day was an exciting one. There was no reason not to be a big kid, put the wheels on, take the axle stands down and get the car on the floor in the garage sitting on its own four wheels.

Even though I’m used to how low Caterhams sit, a few months of it up on axle stands means that you get used to that position, and the car seems amazingly low when they are removed. I pushed it backwards and forwards and made some brum brum nosies 😉

My next build day will be focusing on the boot cover, which needs to go in before the seat belt harnesses. And then the seats can go in. If that goes well, I will start on the wheel arches, but lets not get too far ahead of myself.

I do have the whole weekend in the garage, as my wife and kids are off camping with some girl friends. I have to stay focused and not end up in a pub 😉


Day 8: Rear suspension & brakes

With the diff in place the next main step was to build out the rear suspension. The assembly guide is pretty much spot on in this area, which helps! Well, it’s spot on if you read it, but that’s a funny little story for later on in todays build progress.

First thing to do was squirt a little cavity wax into and coating (lightly) the inside of the DeDion tube. I used the same Dinitrol Cavity Wax 3125 as I used on day 1 for the grot traps.

And today Paul and Craig were supporting, as the A frame and other bits of the suspension are easier done with assistance. We are all enjoying tinkering, and the build continues to be a really sociable affair.

Brake Pipes on DeDion

The first real step was to work out how the brake pipes are positioned down the length of the DeDion. This was all simple once I realised that the final bends in the pipe at the calliper ends need to be manually done. It then all clicked into place and it was obvious how to attach to the tube. Rivets and little P clips made this simple. As you can see from the photo, the guide walks you through “dry fitting” the “ears” and callipers, so that you can easily work out how to make those final bends in the brake pipe.


in order of RHS then LHS these are how we set up the pipes. Beware here, although its easy to sort in situ. The RHS has a natural bend that keeps the pipe low to the tube before rising up to the calliper. The LHS doesn’t naturally do this. We had to tweak this when in place, as the brake pipe would have fouled on the spring and damper unit. The adapter you can see on the left edge of my workbench which the left and right brake pipes fits into is the three-way union. Basically the whole DeDion tube is moving when under suspension load, so this third brake pipe is actually a braided flexible one, identical to the ones used for the front brakes.

A Frame and DeDion tube fitting

I didn’t really take photos of the A Frame and Dedion going in. I was caught up in the moment and simply forgot. My advice would be to protect the lower chassis tubes with plumbers foam cladding, as it then is really easy to rest the Dedion in place.

The A frame is also simple. I mean neither of these jobs is anything like the challenge of fitting the heavy diff. You do have to space the A frame so that the DeDion is central. For me this was exactly as the guide said, an uneven number of spacers on each side. I ended up with 8.2 cm from the edge of the DeDion to the nearest chassis tube parallel to the Dedion, and 8.3 cm on the other side. I’d call that central!


The picture above also shows the rear ARB mounting, a lovely aluminium clamp, just like the steering rack clamp. The only challenge here is getting the rubbers over the ends of the ARB and more specifically around the 90 degree corner at each end. This looked like it should be tragically hard, but you need lots of rubber lubricant and a large flat bladed screw driver to “help” the rubber around the corner. Literally 2 mins for each end and rubber lubricant everywhere!

Springs and Dampers

The springs are mounted at the top via a bolt that is already in place in the chassis, just undo it from inside the cockpit and slip a spacer into the top mount before re-attaching the bolt. The lower mounts needed a little persuasion, but what I did was make life easy and rotate the adjustable platforms tighter (up) to allow me to more easily slip the bolts through.

Notice that in the second picture above, the brake pipe travels very close to the spring. When I had the callipers in place a little later I moved this pipe away. Its very soft so gentle finger pressure does the trick.

Radius Arms

Next step is to fit the radius arms. Key things to remember here are that you torque the bolt into the body horizontally and that you make sure the chamfers in the arms face outwards. This is so that the Callipers just miss these arms when fitted. A really simple job but the lower mount needed a rubber mallet attack to get it into place!IMG_1759

I did need to have a chat with a few folk about which hole to attach the radius arm to. There is an upper position, which I have used, and a lower position, you can see the lower hole above.

Allegedly the upper is the more compliant setting and the lower is the racier setting. The general conclusion I came to after listening to others was to leave it in the top hole. I also took this option because the inner skin has not been fully drilled out, which means it would have been slightly more effort to use the lower mounting holes. I’m happy with my choice, mainly because it was inconclusive and relatively inconsequential….probably!

Drive shafts

The drive shafts were then inserted, which is a simple job, and they are marked LHS and RHS and are different lengths. The splines engaged and they slot in with minimal effort. They need to go in now because the next step is to fit them through the DeDion ears as you fit them.


DeDion Ears, Uprights and Callipers

The assembly guide is weak in this area. There is a really good exploded diagram of the whole of the suspension/upright assembly, one of the best diagrams in the guide, if a little small. But it is completely let down by its legend. There are number bubbles all over the diagram, and different length bolts need to be used, but the legend calls out each of these bolts as simply “bolt”. Its tragic and pretty much impossible to achieve without third party guidance.

And the saviour for this assembly is Andrew Bissell, whose build diary provides very good annotated colour photos of which bolt goes where. I have reproduced them below, and what I did was print them out and reference them throughout. Where Andrew mentions “Ford Bag” for some bolts, I found mine were pre attached to the Callipers in the Calliper boxes.

These diagrams should be added to the assembly guide in my opinion!

My big embarrassing mistake!

In my defence it was late in the evening and I was very tired from a fairly big build day. I had completely made up the LHS uprights perfectly according to the assembly guide and the above bolt photos.

I then moved to the RHS to repeat what I had just done. I guess I was slightly less engaged because I had just completed the first side, and I didn’t take the assembly guide with me from one side of the car to the other.

I just went for it and when trying to insert the hub carrier, I simply couldn’t get it to fit. No matter what I tried, I couldn’t get it to move far enough inboard with the drive shaft attached to be able to bolt it to the ear.

I asked Simon Calvert, also building the same car what he thought it could be, and I was convinced that my RHS drive shaft was too long. I even measured it and asked him to provide his measurement.

They were identical in size and this threw me completely. Simon asked me to send a photo and I sent him both sides to show that I had completed one OK, but the other didn’t fit.

This is the photo. Spot the problem?


Within about 15 seconds he came back and told me that i had fitted my hub carrier the wrong way around. In effect I had tried to insert the fat end into the hole.

What a numpty. I did it right on the first one, but brain fade caught me out on the other one. Fairly embarrassing, I am likely to continue to be reminded of this in years to come!

Brake Discs

Brake discs went on fine, but its really important to carefully read the assembly guide, because there are two little spacers for each side which space the floating callipers so that the brake discs are nicely aligned in the centre of the callipers.



You can see the handbrake cable fitted above. On both sides of the car the cable exits the prop shaft tunnel and is routed over and around the back of the drive shafts before looping back up and entering the front of the callipers as you can see here. The trick is to start with the handbrake lever fully vertical, and then slacken off the big white knurled wheels for adjustment until you have so much cable left at each side that its a simple job to hook the ends over the claw you attach them to. Leave the handbrake lever adjusted like this to make it possible to fit the tunnel top. The handbrake can be properly adjusted right at the end of the build. Or thats what I’m going to do.

Drop Links for ARB and Speedo sensor

The next job should have been a 2 minute one, but it took a lot of effort simply trying to work out what the assembly guide meant. The way the job is described I am missing an extension bar to be able to fit the drop links, but this is a load of rubbish (after checking with others)!


The objective if you follow the guide is to get them looking like the above photo. But the gap is too large between the bracket and the ARB bar, hence me thinking I do need this extension bar. But actually, what you do is rotate one end through 180 degrees. For example, in the photo above, rotate the RHS so that the screw thread points downwards.

This was they fit. But use washers and the Nyloc nuts and bin the extra brass nuts as they aren’t required.

On the RHS there is a hole to insert the speedo sensor, a hall effect sensor. The trick is to line it up with the drive shaft toothed ring and to then get it to within 1mm of this ring, and the theory is it should register speed correctly. We will wait and see, but it looks simple to adjust if I need to.

End of day…

And so that was it for Day 8. I’m a little bit behind writing up this build blog, so I’ve also already completed Day 9 in my garage. So for the next instalment, I will be writing up testing the electrics and sorting out the interior and boot of the car. I’m now formally into the fiddly small stuff that seems to take an age!


Day 7: Complete front end

But just before completing the front end…

I finished the diff on day 6, but didn’t fill it with the diff oil or LSD additive. I decided that based on the volume, I could probably fill the diff with it in place, and without the drive shafts fitted. I thought that I would take this slowly and fill properly from the drain plug to ensure I got the correct volume of oil in the diff, and lost none from the drive shaft holes!

So this was a really straightforward operation, with the exception of the fact that the diff drain plug is a rather large hex bolt, so I needed to buy a 14 mm allen key socket to remove. I could have filled via either side of the diff, but ultimately I need this socket for regular maintenance and top up purposes.

I used a small funnel and some clear rubber tubing, and attached the funnel to the car with a tie wrap. All very painless. And for reference, you can fill the diff using the whole of the 1 Litre bottle of oil and the LSD additive and it takes the whole lot, but starts dribbling back out of the drain hole in the last few ml, and this is the sign you are looking for to validate its full.

And no oil came out of either side, so this is a job that is good to do at this point, when you have a little better access before the rear suspension goes in.

Water expansion bottle mounting plate

On a 420R, the oil tank for the dry sump kit is attached to the centre top of the cruciform, so you have to move the water expansion bottle off to the right hand side of the car, by attaching a plate to the top of the chassis tubes.

Two minor challenges with this small job are the fact that the plate to attach to the chassis is a rubbish fit. It wouldn’t take much effort for Caterham to create this plate to actually fit the chassis tube angles, but unfortunately they never have. My assumption is that it’s a plate designed for the S3 as the angles of the top tubes may be very slightly different, and they just “made do” for the SV.

The second challenge is that drilling holes into round chassis tubes isn’t fun. Once I decided on the hole location, I used an awl and a punch to gently make 4 big enough marks to attempt with a pilot drill bit. I then gradually moved up to the final 4mm bit size. The shape of the plate meant that not every hole was lined up along the centre line of the tube.

Roll over bar

After the “fraught with danger” expansion bottle bracket mounting, it was time for a really easy job. I attached the rollover bar. My variant is the FIA bar, so that means a thicker stronger tube and two additional mounting points. This has to be completed before the rear coils and dampers are fitted, as in addition to the top mount bolt you can see in the photo below, there is another bolt that goes upwards into the base of the roll bar from where the suspension will be. Its simple, especially when you realise that you can undo the long bolts that will be the top mounts for the suspension from inside the car.

Exhaust system

This is a one man job, but Paul was around to help and it made the job a little easier. He could hold the primaries in position whilst I torqued up the bolts into the block. My primaries were marked up before I sent them off for polishing, and of course when they came back, there were no labels on them.

To be honest, its dead easy to work out which is primary 1,2,3,4 from simply placing them like a jigsaw puzzle on the floor. For an SV, the insertion order is 4-3-2-1, so in effect start from the furthest back on the engine.

In my case, I had already completed the steering, so I had to angle the primaries around the steering rod too, but this was no problem. Primary one goes over the steering rod, and that was actually inserted from the top, rotated a little to get through the hole in the side skin and then rotated back. I used offcuts of bubble wrap to protect the side skin around the exit hole.


Once loosely bolted in place, I attached the collector (catalyst), and its a simple interference fit. A little alignment and a gentle tap or two with a rubber mallet, and it slid on easily. So far so good. The harder piece is attaching the “reverse springs”, of which there are 2, and these ensure that the collector remains tight onto the primaries.

I’d previously read on another blog that this can be made easy with a bunch of tie wraps. So, with the held from my vice and 4 tie wraps per spring, I compressed the springs all the way and the just about slipped over the hooks on the exhaust parts. I still had to use a little copper slip and a gentle bash from a mallet to get the hoops to slip over the hooks.

I imagine that if I didn’t know about this trick, I’d still be in the garage now chasing springs bouncing around!

Finally, the back box and the collector heat guard completed the job. The back box fits more loosely over the rear of the collector, and a bracket is provided to draw these two pieces tightly together.

And then a small L shaped bracket for the rear mount, with a rubber exhaust bobbin and a few nuts to attach and the job is done. The whole exhaust was done in less than an hour, so felt rather pleased, and I love the polished completed exhaust in situ. Of course the moment its been through a heat cycle or two it wont look like this, but in years to come I can reminisce by looking back at this photo! (did I tell you that I’m not a polisher?)

Cowling, ARB, Radiator, Oil Cooler

I’ve previously mentioned that the rear cowling for the radiator needs some rework to enlarge the slots in order that the front ARB will clear the sides of it. I achieved this with a Dremel and a metal file, and although I’m not going to win any metal works awards, I was quite pleased with the end result. Thanks to Dan Smith for sending photos and measurements of his enlarged slots, and here they are for future self-builders:

In effect, this was a relatively simple job, but it’s all about the order of assembly. The manual tells us to fit the inner cowl before the ARB, but as you c an see from the first photo below, there is enough wiggle room to rotate the cowl up and under even if the ARB is in place. The SV has some additional brackets because tis slightly wider than the S3, but the radiators are the same. The manual here is a little poor, and it needs a few good quality photos of the layout.The photos I have taken should really help with “what goes where, and on top of what”.

Everything fitted well, but note that the oil cooler needs its top mounting holes drilling. This is simple from an alignment perspective, just attach to the lower holes first. I did have to gently bend the oil cooler bracket to get it to sit straight, with the bracket mounts aligned vertically up the sides of the radiator. In the final picture you can see that I have attached the oil pipes.

The diagram in the assembly guide is perfect for this, it really simplifies what goes where with respect to the 3 oil pipes you have to attach – sorry no photos here, but it really is simple in terms of what connects where, and the oil hoses are only just long enough to fit, which means that routing is based on shortest distance through the chassis rails.

Oil and Water hoses

This is a picture of how I attached everything. The only item I was missing at this point was the water return pipe for the expansion bottle. Caterham simply hadn’t provided one in the kit, so a quick phone call to Derek and the following day the hose arrived. I cable tied it neatly directly under the top left (from the perspective of this photo) oil hose from the oil tank that you can see in the picture below.


Heater hoses

Fixing the heater pipes requires a Stanley knife for chopping up bits of hose, but other than that it’s simple. What is more of a pain is that the manual is painfully rubbish when it comes to the instructions for the where these hoses terminate. The final picture below shows that the heater inlet (top) is the hose that goes down to the front LHS of the engine,, and the heater outlet (lower), goes around to the rear RHS of the engine, where there is an inlet. It does this via the water temperature submarine and a chopped up J hose, with just the curvy J to double back. The green wire from the loom very close to where the submarine is, is inserted into the temperature sender.


Unfortunately, I have done this slightly wrong in this final photo. The assembly guide does not mention anything about the black and yellow wires that are floating around in the same area. I heard from Simon Calvert, another self-builder, that this is the earth to the submarine, and that if you don’t attach this then the water temperature gauge does not work properly. All of the 420R kits seem to be missing a metal adapter that coverts this black/yellow connector (bottom, middle below) into a hole to attach to the screw thread on the under side of the sender. Nothing in instructions and no part = minor frustration. What this means is that I will move the hoses UNDERNEATH the black plastic plate, not above as you can see here below. This way I get access to the threaded bolt on the sender, which is currently screwed into the plastic plate.


The routing of the water hoses caused me a headache to the point that I knew what the manual meant, but I wanted a little peace of mind and validation. As luck would have it, I’m building my car around the same time time Dan Smith and Simon Calvert are doing theirs. Dan kindly sent me a video of the water hose routing and has kindly allowed me to post this here:

I also completed the heater build by attaching the heater cable from the underside of the dash all the way through to the heater valve, which needed a tiny amount of adjusting to ensure that the valve moves from fully open to fully closed.

At this point I also fitted the throttle cable, but took no photos (I’m almost as bad as the assembly guide, sorry!). This was easy once I worked out that I had to cut the nipple off the throttle peddle end, thread it through the slot and hole, and then secure on the other side. Many other self-builders use the brass inner wire gripper from a standard electrical joining plug (not sure what their proper name is!) I used this method too, and made sure that the throttle pedal movement fully opened and closed the throttle body.

Air box woes, and other misaligned holes…

Now onto what should have been really easy. The air box sits on 3 small rubber bobbins, as per the photo below. What happened with my car is that some bright spark at Caterham decided to use the template for drilling these 3 riv-nut hole from the S3 model. Which means that I am left with 3 holes that are about 4 cm too far “outboard” which means simply that the air box will not fit, the hose doesn’t really reach the throttle body and is a long way offset, and the cold air inlet that should butt up against the bonnet is also outside the car by 4 cm. Its tragic…


See the air box as I can position it:


I am not happy with this, as the suggestion by Caterham is to drill another 3 holes in the horizontal scuttle in the right place. But I paid a lot of money for this kit, and I don’t want 6 holes in the car when I only need 3. Caterham has agreed to rework this scuttle at the Post Build Check, and has apologised for this error.

As a temporary solution, I am going to retain the 3 bobbins in position, and make some metal extension bars that move the air box inboard, imagine like some pieces of Meccano.

And finally, whilst we are on the subject of hole placement, the nose cone badge is supposed to fit on top of the 2 holes pre-drilled in the nose cone. The badge has two fat pins on its underside which locate in the holes.

It looks like the same person responsible for my air box holes has been working on the nose cones too. I posted these pictures on Facebook and the comment that made me laugh most was that its totally fine, just a parallax error and it looks central from a certain angle…

Someone else then posted a load of new bonnets photographed in the factory under my facebook thread. If you zoom in I don’t see one of these bonnets that has central holes.


From a chassis and part engineering quality, the whole kit is top notch and tolerances are fine. Its the final stage simple work such as drilling these air box and bonnet holes that REALLY lets Caterham down in my opinion.

Anyway, even these two little problems aren’t spoiling my enjoyment, and Derek from the factory is extremely good at customer service, and progresses any issues or shortages to my satisfaction.

Day 7 efforts have really moved my build on. I now have the whole front end down, and everything wired up and plumbed in properly. I have yet to fill with fluids (with the exception of the pre-filled gearbox and the diff), but now its time to move rearwards and get my head around the rear suspension and brakes. But that’s for another day!