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Sierra Cosworth IP build

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Hi All,

Thought I would start up a thread on a build I am in the middle of at the moment - a 1987 Ford Sierra Cosworth. Sorry but this first post will be a bit of a long one as there has been a bit of work done to date :)

I am building the car to compete in Improved Production Racing in Aus but will also run it in some other classes where I can.

I picked up a pretty bare shell about 10 months ago -

And immediately go to to work prepping it for the track. The shell itself is in pretty good condition with very little rust and is very straight so not a lot of work is needed in that regard, leaving most of the work required in getting it race prepped. First thing to do was to get everything stripped out of it that was not needed (and was allowed to be stripped out under the IP rules). Most of the interior was out of it when I got it so that wasn't too much work but there was a lot of fun removing body deadener etc.

Under the IP rules, I have to retain the original dash and MK1 Sierras are renowned for dash's cracking and this one was no exception -

I got the dremel out and cleared out all the dead material and prepped it for filling in with an epoxy filler.

After which I sanded it down and then floc'd the dash -

The first go at floc'ing it was a bit of a failure - i tried to use a thick 1 part epoxy paint as the "glue" but it was not think enough, set too quick and the fibres did not stick very well. I ended up sanding it back and then using a standard fibreglass 2 part epoxy resin with 30 min catalyst which gave me much more work time and ended up in a much better finish (as well as adding some overall strength to the underlying dash so hopefully it wont crack again) .

After chatting with one of my local suppliers whom I have known for a long time, I decided to go with a NZ made RaceTech seat, going with one of the RT4119 seats, the main reason being the extra mounting points on the shoulder points of the seat which tie the seat into the cage better and also work to tie the car together a bit tighter as well.

The main thing when going with one of these seats is that seat - main hoop location are critical - once either one is locked in you do not have a lot of scope for moving the seat back or forth so a lot of planning needs to go in before you start with the cage, seat mounts, pedal position etc and category rules all need to be taken into account as well - in IP you are restricted with how far back you can move the pedals, so there was a lot of moving things about and measuring before a seat position was finalised and mounts could be started.

Once the seat position was locked in, I could get started on the cage.

This was my first go at building a cage but meant I got to buy new tools which is always fun!

There was a bit of trial and error in getting started with I but managed to get the swing of things after not too long. There was 2 goes at making the main hoop, with the first go coming out a bit out of whack after the tube rolled in the die between bends -

But managed to get a good tight fitting hoop on the second go -

After that, it was onto front bars -

And then side bars and everything else followed from there -

Unfortunately, the latest regs for CAMS cages require you to gusset the A-pillar bar with at least 2 gussets at any join which meant I ended up with this masterpiece of gussets -

The rear came together pretty cleanly, with the main focus point being to ensure the seat shoulder bar was in the right spot (heigh of the bar is critical when using HANS devices as they are particular with seatbelt angles) -

With the cage out of the way, next step was to sort out mechanicals. I am going to run a Cosworth YB 2L turbo engine but due to the requirements of IP, I will need to run a 36mm restrictor on the turbo which means HP will tap out at about 400 bhp on E85 and revs will tap out at about 5800 - 6000 rpm. This turns the build into a chase for torque with high levels of boost low in the rev range which doesn't sound too bad until you consider the strain on the driveline by pumping through crazy amounts of torque with gearing to suit low revs. I got lucky with the diff when I managed to track down one of the Harrop Engineering Ford 9" GrepA Sierra diffs like what DJR ran in the day -

Which should prove to be up to the task and a hell of a lot stronger than the standard 7.5" that would normally run in the car -

I also managed to track down some GrpA drive shafts which should keep the rest of the driveline in shape, leaving only a gearbox.

Trying to keep things as simple (and cheap) as possible, I had a couple of options. The road car runs a Borg Warner T5 which is custom made for the Sierra Cosworth (input shaft, output and gears are different to the Mustang versions) and in standard form would not be up to the task. A couple of companies made big tooth gearsets for them and one company made big tooth dog sets for them but it was proving very difficult to find them and there was still some doubt as to wether the resulting box would take the torque.

The GrpA cars ran Getrag 265's in the early cars and then Holinger GRA-5 boxes in the later Australian cars - both boxes ran the same bellhousing (as the GRA-5 was modelled heavily on the Getrag at the time) so if I could track down one of those boxes and a bellhousing, I would have a strong solution with an easy fitment - not an easy task though! The downside to the Getrag option is that they are a syncro box whereas the Holinger is a dog-box.

The other option was to go to someone like Holinger, Samsonas, Drenth etc and get one of their current boxes and then get a custom bell housing (or adapter for the std one) made but this was looking like an expensive option that I didnt want to spend to get the car on track for the first season.

In the end, I got lucky again and someone locally was selling a Getrag 265 that had run in a GrpA Sierra so it had the correct input shaft which had been upgraded with a Samsonas 6sp dog gearset so jumped on that -

Which only left me with a bell housing to find.

These bellhousings were only made for the GrpA Sierras 30 years ago meaning there were only say 30-50 of them made and they are like hens teeth now but after much searching the world I managed to find someone in the UK that was remanufacturing them so after some back and forth got one ordered and shipped over.

The GrpA setup places the gearbox much further back in the car than the std setup helping weight distribution.

Some strut braces were knocked up front and rear -

To ensure the suspension would not cave the towers in -

I went with GAZ shocks from the UK with 3 way fronts and 2 way rears. They are not a cheap setup but a long way from a top end race setup but I thought I would give them a go to get the car on track and see how they go, if they dont perform as desired then I will probably look at a custom set of MCA golds or similar.

Moving on to brakes, I am aiming to keep the car around the 1050 kg mark so didnt want to go stupid on brakes and also wanted to keep the car on 17's rather than step up to 18's - I feel the Sierra will perform a bit better especially in the rear with a bit more tyre wall to work with and it helps keep weight down - so aimed for somewhere around the 350mm mark for the front. I ended up getting a new pair of AP CP5785 RadiCal callipers which I must say are absolute brake porn -

They are a 1 pice billet calliper with Titanium pistons weighing in at sub 2kg ea, designed for up to 380mm rotors. Once I had them locked in, I chose to go with a 343mm disc as it was the disc used on the rear of the V8 Supercars until the most recent update meaning spare rotors are easy to come by.

After getting that sorted, I worked with Brypar to get some new discs made up as well as a set of hats and calliper adapters to mount it all up. Whilst I was waiting for the work to be done I decided to run a 3d print of the setup and test fit-up -

Which was good as it highlighted a couple of fitment issues which were able to be remedies before machining. The final product:

After much umming and ahhing deciding what to do re a pedal box due to the restrictions placed by IP, I decided to go with a Tilton underfoot floor mount pedal box -

And also knocked up a template for the false floor and a foot rest -

Then it came time to install some motivation in the workshop -

I had had the poster sitting in storage for the best part of 20 years and thought it best to get it out!

I managed to track down a couple of new windscreens for the car in Aus -

And about 2 weeks after buying those, managed to find a heated motorsport screen for the car in Aus so grabbed that as well -

So will run with that and hope I never crack it (it was 3 times the price of the non heated screens!)

Work has been a bit slow over the last few months due to another racing commitment I had which finished up in August so since then it has been full steam ahead. The bit that has been taking up a lot of my time of late is planning for wiring which is almost at a implementation phase. I am going pretty full on with the setup, including 29 sensors on the car, Motec M880 ECU, 2 x Motex PDM15's, Motec CDL3 dash, Motec DBW-4 and Motec 15 button CAN keypad so the planning has been pretty full on. Last weekend I started running rope to get wire run lengths and also visualise where and what is going into the car.

And I hope to have that finalised this weekend after which I will start work on the interior side of the loom - the car needs a full engine and chassis loom made so that will take a bit of time, especially considering that like the cage, this will be my first go at making a loom.

And finally, today, I had a delivery from the UK, with my rear brake setup -

I went with a setup of AP CP9441 Pro 5000R callipers with 315x25mm discs which I think should balance out nicely with the 343's on the front .

This weekend will see some progress on the wiring with that being the main area of work for the next couple of weeks whilst also souring plumbing for the brakes now that I have all four corners as well as sourcing the fuel system. I have all the components for the engine except for a set of pistons which I have on order from Cosworth Engineering in the UK which should show up in the next couple of weeks - I will be doing the engine assembly myself but will get someone to pull the string on it and tune it when the time comes.

Thats it for now, but will post more as it progresses from here.

Hmmm, I really like this car porn!

However, I would get your local scruitineer to check the cage welding - might be the photo's but doesn't seem quite right - and better to do any remedial work now than later?

Any welds in particular or just in general?

CAMS has checked it and issued a certificate of compliance but if you think there is anything wrong I would be interested in hearing as like you said better to fix it now.

Must have been the photo's, some maybe looked like they were a bit too hot and some a bit lumpy/cold - but it's been inspected in person, by someone who is experienced, so it's all sweet as :-D