1985 FB Restomod

[RB6102]

A couple of months back I acquired two RX7s here in Devon. I've been gradually working through the better condition silver car, starting with the mechanicals but also gathering the missing bodywork panels. I got a couple of rear repair panels shipped over from thse states and was going to get a pair of brand new wings as well but the shipping costs were going to be huge! I got myself some correctly fitting front wings from RX Motors in the end. They're not perfect but are solid at least.

The first job was to inspect the condition of the engine. It has always run fine but seemed a bit down on power so I decided to run a compression test on it. Both housings were similar at a very low 60ish psi. I know there are proper testers that check all three compression chambers but I just wanted a feel for how worn everything was. After tearing down the spare engine that came with the car I did not have high hopes for this one either. Sure enough, after buying a bore scope (a cheap usb type off eBay that plugs into your phone - very impressive for the cost) and having a look inside I could see flaking of the chrome and some rust at the bottom when liquids would settle. I've decided to take this engine apart and see what I can salvage from the two..

Meanwhile, I've also had all the calipers off the car to rebuild them. Some of them were very tight to free up but nothing an adaptor on the inlet port and a quick blast from the air line couldn't sort. Ive cleaned eveverything up and it will all go again with new seals etc, all apart from one of the rear pistons. It's not a simple part otherwise I'd probably have just machined a new one but I can't find a source for them anywhere. I've tried RockAuto, my local Mazda dealers etc with no luck. Any other ideas from anyone would be appreciated otherwise I guess I'm on the hunt for another caliper.

I've also been working on the suspension upgrade I plan for this car. I'm using the shocks off the second car as donors so the good car can always remain mobile then I'll swap them over when I'm done. Starting with the fronts I've cut off the tube and machined out the bore of the forging back to stock ready to accept an adaptor and a new tube to allow use of a bigger main piston and 2.25" bore coils. This will be a completely bespoke setup of my own design. It's what I do as my day job but for other cars, I just want to work on my own vehicle for once! The only hiccup here was one of the main bolts holding the steering assembly to the bottom of the strut had sheared off! No problem to sort just extra work to get the parts I needed to carry on.

Progress will be slow at times but I'll try and keep updates coming for those that are interested.

[DKWW2000]

Great work Rob you seem to be making great progress, reference the caliper, put a ad in the "Wanted" section, I am sure someone will have one. I hope you you are taking lots of pictures especially the front struts, we would all love to see your work on them.

regards Pete

[RB6102]

Thanks Pete, will do.

I am indeed taking lots of photos:

[RB6102]

Progress update. I've cleaned up the inside bore of the stub axles, made up the adaptors to allow welding to larger damper tubes, made the tubes and the top caps. For the internals I've made the pistons and machined one end of the damper rod.

I need to tack weld the parts together and machine the top end of the damper rod to suit the top mount hole then I'll be able to offer it all up to the car and confirm fitment. Working on using the standard wheels and tyres I'll be checking maximum bump travel for clearance all around and at all steering locks.

The main tubes are sized to accept an off the shelf coilover adaptor or I may reattach the standard lower perch. The larger bore of the tube allows a large main piston and gas pressurised reservoir, doing away with the original cartridge design.

Ive started to have a look at the rear shock installation but from what I've read clearance for a coilover setup is tight!

[RB6102]

[DKWW2000]

I have seen them in the flesh & they are as good as, if not better than they look

[RB6102]

I made up the top mount adaptors last night and set the tube and rod lengths to match oem mazda. I'll shortly be able to offer it up to the car and see how much lower we can go! Stock mazda insert is on the left and my two dampers middle and right.

[spirit r]

Very professional inspirationed work!

Do you have a better picture to show us the point how the pipe was fixed

DSC_2307_zpshtsgxtlh.jpg (126.85 KiB) Viewed 11634 times

[RB6102]

The original tube is approx 45mm OD and 39mm ID with a solid cap at the bottom. It was pressed into the upright from the top then welded at the bottom. This seems to be how many older cars like this were assembled: Porsche, BMW, Toyota etc.

The adaptor I made goes into the upright then allows me to fit the 50.8mm / 2" main tubes. This 2" diameter will allow using coilover conversion sleeves as well.

[RB6102]

I finally got the struts fitted for checking on the car. I have improved the design so now I have an inverted front setup using modified 40mm Bilstein inserts. The inserts were originally for a Monaro CV8 which I have shortened to suit the Mazda. Off the shelf outer tubes for making your own struts are available from motorsport suppliers but I made my own tubes instead as I wanted to reduce the friction in the system. Normal Bilstein type inverted struts have the insert running in two bushes that remain fixed in the outer tube. The struts I have made run a fixed upper bush but the lower one is fitted to the end of the insert instead. This gives more support overlap reducing friction and a more precise feel.

Normally if you want to re-valve the inserts you have to send them away, but instead I drilled into and let the gas out and modified the top to include a gassing port for rebuilding. I also managed to hack into the internals, got the staked nut off that holds the piston and shims on rod. The shims are the same size we used at work so was able to re-valve them for use in the Mazda.

With the inserts ready to go I welded a coilover kit to the outer tube and modified the top spring platform to work with the damper top and top mount then fitted it all to the car. I've since checked and confirmed fitment so they can come off the car for final finishing and paint!