Luke's FD RX7 - FDL98

[lukevl]

I’ve been meaning to write this up for a while but any spare time I had was donated to the build. So now I’m stuck on a plane and already watched Deadpool twice so figured I’d do this. Update: Didn’t finish it back then so I’m having another go. Update 2: Ok third go now and it’s about 6 months after the first attempt. Same long haul shit flight pretty much so anyway here we go. If shit doesn’t seem like it’s in order that’s because it’s not completely and I started this build almost 2.5 years ago.

I swore I wouldn’t own a cross purpose car after my last one which was registered and sucked at being a street car and sucked at racing too. I want a dedicated track car so there are no difficult decisions or compromises to be made every time I want to make a modification. Plus driving on the roads in Australia without losing your licence is about as risky as sharing a crack needle in Africa so having a big HP street car was not what I wanted.

Then at some point I decided that past Luke was wrong and I can totally make it work this time. Dick. So the theory is procure one of my hero cars, an FD3S RX7, because I’ve always wanted one however I can’t speak rotary. So I then remove the unwanted bits (anything with oil) and then plug in an LS because it’s proven, simple, relatively un-stressed and doesn’t completely destroy the chassis balance (TBC). Some brief research suggested not a huge weight increase over stock, fitting kits available, and been done quite a bit before in the USA so lots of information out there. I like having something different but I’m too time poor to pioneer something from scratch and make my own conversion bits. So in the end I would have a compromise car that would not be the quickest in any area but should be plenty fast enough on the track to be enjoyable while still being a well behaved street car despite the obvious entry-egress issues.
So I picked the car up from Rotorhead16 on here back in about May 2016 with a pretty sad motor. The car itself is a MY2000, Series 8, Version V, Type RS and it is very clean and genuine low-ish kms (90k). The Type RS is a pretty cool variant (there are fifty billion special edition FDs- see Bab’s thread) because it comes with larger brakes, higher power turbos, twin oil coolers, 4.3 diff ratio (up from 4.1), different box (taller fifth) to account for the diff ratio- ie a bunch of functional stuff as opposed to trim pieces. This particular car also came with aftermarket bits that were either good to keep or sell- Apexi PFC, Trust intercooler, SMB/HKS exhaust, AST, Cusco coilovers, and 2 sets of rims- fancy Work Meister 18s and my personal favourite- Rays Gram Lights 17s. I envisage the car having a bit of side wall and a bit of ride height to go with the donkey V8 muscle.

So the deal was done, Josh wound the coilovers up a bit for transport and it was trucked up from Canberra to Brisbane after much rooting around with Ceva’s retarded logistics.





First thing to do was take the bits out I don’t want and sell them.

This thing



That thing



These things













The surplus components fetched some good money without having to be a dreamer seller and arguing with people that turned up. So the next thing to do was source the bits I definitely knew I neede.

Fitting kit from Justin Samberg in the US to suit the LS and T56 into the FD. I got the engine and trans mount kit which is made up of front subframe, gearbox crossmember, bump steer relocation kit, DBW throttle pedal mount.






I picked up a Samberg radiator and header tank kit from Walt Kowalski on here because he had a spare and there were some shipping issues with the unit from the US being damaged apparently.

[lukevl]

Like the MX5 the FD comes from the factory with a power plant frame which is a spine that joins the gearbox to the diff so it creates a rigid powerplant from front of the engine right through to the back of the diff. So then all you have are engine mounts and diff mounts and that hangs your powertrain as well as resists torque and pitch moments. So if you take the engine, box and PPF out, the diff needs additional mounting to resist axle torque (as does the gearbag). I decided that since rotaries don’t have enough torque to peel a potato I should get a different diff. I bought an aluminium housing Ford 8.8 diff from Justin along with his fitting kit (partial subframe that ties in with the OE rear one) and some upgraded axles and billet 108mm Porsche style inner CVs from the Driveshaft Shop in the US.

The diff mounted in the cradle and subframe easy enough and only needed some minor die grinding. I’d rather that though than holes that are oversize. It supersedes some of the OE bracing too so in the bin for them.











The diff was rebuilt by Diff Lapping in Brisbane and has new FoMoCo diff gears, new Torsen 2 centre, bearings and seals. Now the diff gears- this was a tough one. After driving one LS FD (thanks mxpaul), witnessing another driving in anger, and reading complaints from some who have done the conversion but hate the dopey truck-like gear changes, I looked into it and realised I didn’t want 4.XX gears. First port of call is to check what diff ratios the donor car has- 3.27 and 3.45 in the HSVs. Factory FDs have 4.11 and mine had 4.3. Sounds like never ending gear changes which I kind of confirmed with other cars using the OE diff gears. Sure the T56 has 6 gears but I don’t have to use them all- I have the box, it fits, it works so I don’t care if I never use 6th and to be honest I’d probably rather only use 3 gears at the track. So my decision quickly became somewhere between 3.2 and 3.7. I had no doubt longer gearing is where I wanted to be because the car will be much lighter than a commodore and the motor will be built for a fat torque band so it can lug longer gears relatively easy. I was very close to going longer but I ended up with 3.55:1 which I think should be good and gives a usable first gear on the street.





Here is a graph of the road speed gearing. I briefly contemplated stumping up for a T56 Magnum but for various reasons (one of them being the $5,500 price tag) I didn’t go ahead. One of the main reasons was that to have a close ratio box first is a bit longer and I want this to be a usable street car.

[lukevl]

For the motor I decided I wanted an L98 because I didn’t want to pay for an LS3 and 6.2 is borderline on the capacity limit under NCOP and didn’t want to risk it. Plus the L98 has the L92 heads but no DOD so pretty much ready to go. It came from a VE SS ute with the TUET8381 box which is apparently a T56 box with a TR6060 extension housing and some other minor changes. Also came with the ECU, wiring loom and throttle pedal.



The first test fit went quite well. The motor dropped in quite easily. I had to cut the back of the manifold cover but nothing serious (I didn’t end up using this anyway). The body was drilled for the gearbox crossmember and the engine and box were mounted.







Even the shifter lined up nicely

[Mc Juicy Hairy Balls]

No mention of mgw shifter? I like this and its made easy using kits....like wow. Sweet. Will be mean cuz

[lukevl]

This is why I added the disclaimer that it wasn't necessarily in order. If I documented it in actual order it would be a fucking mess! MGW shifter chapter is coming- it's a bad-ass bit of kit

[Greg Rust]

Hell yea nice build.

[Grizzler]

Any info on the MGW shifter? I've heard on here they are pretty good.

[lukevl]

I don't have the relevant pics with me but I'll update tomorrow night when I get home. It's a nice shifter

[neil_se]

Looking good. I'm jealous that you'll get to drive yours on the street.

[Slides]

Nice project. Should be great to drive.


After looking at the effort required to do driveline swaps I'm thinking i might buy a written off shell to practice floor chop for seat lowering and half cage/corvette "its not a transaxle the oil isn't common" transaxle.

[Sonicevo]

Nice work, love FDs, you're game to be modifying it when they're set to go stratospheric in value over the next five years but good on you doing what you want. Should be a good reliable thing on track. Are you doing all the work yourself?

[lukevl]

Ha yeah well to both of you wait until we get to the part where we need to fit me in the car. I'm 6'7"..

I don't plan on selling it ever if it is as good as I hope

[darkside]

This is all kinds of win. Rotorlyfe can tend to break your heart. Cracking chassis with some V8 reliability has to be a good thing.

[Walt Kowalski]

Great stuff. Keep an eye on the OEM welds where the Samberg Diff brace bolts on. Mine tore the OEM welds out and I ended up re welding the OEM bit and bolting it for good measure. Rest of FD chassis has been fine.

[lukevl]

Are you using the 8.8? I didn't see anything obviously wrong but I'll have another look. Thanks Steve