Hello! Long time lurker, infrequent poster - I'm sure I had a thread on here for this car (in it's previous guise) but I can't find it, so...
A few pics from last year to give you a quick idea of the car
The car has a full stainless exhaust system on it which was custom made last year
Recaro's out of some other car, with custom made/adapted E21 frames on them
Custom made front coilovers using a coilover sleeve kit, 2.25" springs and bilstein B8 shocks
It's a 1981 BMW E21, originally a 316 running an M10B18. That was removed last year to make way for a fantastic M42B18 lump. I ran that for most of last year and while it was a great engine, not quite enough power and still a bit too boring for me.
Then the time came to replace my RX8 track car with something else (R53 mini for those that care), and a naughty part of me decided it would be a great idea to swap the rotary lump into my humble old E21.
Work started about 4 weeks ago, the RX8 was pulled up to the front of the garage where it sat face to face with the E21. I swiftly removed the M42 lump from the BMW and set about tearing the RX8 apart - jesus they are well put together!
Decided not to go for a full front end swap....
Eventually, I had the RX8 engine & box out, both interior/exterior looms removed and the propshaft out.
.....CAUTION - doesn't say anything about cutting it up and welding it to an E21 prop.....
I set about removing any unneccesary wiring from the looms, ABS, air con etc. (...a job which still isn't quite finished)
No picture of this, it's just not interesting in any way
Yesterday I managed to 'fit' the RX8 clocks into the E21 dash. It definitely doesn't look pretty but it's a sacrifice I'm willing to make. Getting the E21 clocks to work would have been a nightmare and still would have left me without a speedo.
Drive by wire accelerator pedal also fitted, this was far too easy thanks for the mounting holes on the DBW pedal, drilled 2 holes, cut away some of the carpet and bobs your uncle.
Then I removed bulky parts from the rotary (exhaust manifold, A/C compressor, coolant hoses) making it easier to clean up and drop into the BMW for measurements.
Today lifted it up and dropped it in for the initial 'trial fit', suddenly the gearbox looks far too big for the E21...
And yes - the gearbox/bell housing is FAT, so clearance around the tunnel is mega tight and really is the limiting factor on how far back the engine can sit. Ideally I'd have it 6" further back, but I'm not prepared for cutting and fabbing up a new tunnel. It's still not too bad, it sits further back than the M42 4cyl lump did and it's a much lighter engine so...
Gear lever mount is about 3 inches forward from stock, shouldn't be an issue. Hole enlarged as required...
Stuff not photographed but now an issue is;
Exhaust manifold - It's at the bottom of the engine on the drivers side. The steering column/link sits right across the exhaust outlet ports. I might be able to use the stock manifold, but it's definitely going to need butchering to fit. If not, I'll have to get a fully custom one made.
Sump - sits right over the top of the subframe, not ideal as it means the engine has to sit quite high and at an angle. It's only steel so I think I'm going to drop it off and chop out the rear section, weld it up and hope for the best. Oil pick up is in the middle of the sump so won't be an issue.
Engine/box mounts - Engine mounts conveniently sit right on the chassis rails, so I just need to get the above bits sorted out, confirm engine position and then find some small-ish rubber disc style mounts. Hopefully be an easy job. Gearbox is a bizarre mouting system on the RX8, it uses a brace that goes all the way back to the rear diff, not something I can really replicate on the E21, I need to look into maiking a simple cross brace under the tunnel with a rubber mount on it.
....and that is where I am currently up to as I write this.
Thoughts and opinions welcome and thanks for having a read!
Regular pictures/updates on my instagram @danhargrave
A few pics from last year to give you a quick idea of the car
The car has a full stainless exhaust system on it which was custom made last year
Recaro's out of some other car, with custom made/adapted E21 frames on them
Custom made front coilovers using a coilover sleeve kit, 2.25" springs and bilstein B8 shocks
It's a 1981 BMW E21, originally a 316 running an M10B18. That was removed last year to make way for a fantastic M42B18 lump. I ran that for most of last year and while it was a great engine, not quite enough power and still a bit too boring for me.
Then the time came to replace my RX8 track car with something else (R53 mini for those that care), and a naughty part of me decided it would be a great idea to swap the rotary lump into my humble old E21.
Work started about 4 weeks ago, the RX8 was pulled up to the front of the garage where it sat face to face with the E21. I swiftly removed the M42 lump from the BMW and set about tearing the RX8 apart - jesus they are well put together!
Decided not to go for a full front end swap....
Eventually, I had the RX8 engine & box out, both interior/exterior looms removed and the propshaft out.
.....CAUTION - doesn't say anything about cutting it up and welding it to an E21 prop.....
I set about removing any unneccesary wiring from the looms, ABS, air con etc. (...a job which still isn't quite finished)
No picture of this, it's just not interesting in any way
Yesterday I managed to 'fit' the RX8 clocks into the E21 dash. It definitely doesn't look pretty but it's a sacrifice I'm willing to make. Getting the E21 clocks to work would have been a nightmare and still would have left me without a speedo.
Drive by wire accelerator pedal also fitted, this was far too easy thanks for the mounting holes on the DBW pedal, drilled 2 holes, cut away some of the carpet and bobs your uncle.
Then I removed bulky parts from the rotary (exhaust manifold, A/C compressor, coolant hoses) making it easier to clean up and drop into the BMW for measurements.
Today lifted it up and dropped it in for the initial 'trial fit', suddenly the gearbox looks far too big for the E21...
And yes - the gearbox/bell housing is FAT, so clearance around the tunnel is mega tight and really is the limiting factor on how far back the engine can sit. Ideally I'd have it 6" further back, but I'm not prepared for cutting and fabbing up a new tunnel. It's still not too bad, it sits further back than the M42 4cyl lump did and it's a much lighter engine so...
Gear lever mount is about 3 inches forward from stock, shouldn't be an issue. Hole enlarged as required...
Stuff not photographed but now an issue is;
Exhaust manifold - It's at the bottom of the engine on the drivers side. The steering column/link sits right across the exhaust outlet ports. I might be able to use the stock manifold, but it's definitely going to need butchering to fit. If not, I'll have to get a fully custom one made.
Sump - sits right over the top of the subframe, not ideal as it means the engine has to sit quite high and at an angle. It's only steel so I think I'm going to drop it off and chop out the rear section, weld it up and hope for the best. Oil pick up is in the middle of the sump so won't be an issue.
Engine/box mounts - Engine mounts conveniently sit right on the chassis rails, so I just need to get the above bits sorted out, confirm engine position and then find some small-ish rubber disc style mounts. Hopefully be an easy job. Gearbox is a bizarre mouting system on the RX8, it uses a brace that goes all the way back to the rear diff, not something I can really replicate on the E21, I need to look into maiking a simple cross brace under the tunnel with a rubber mount on it.
....and that is where I am currently up to as I write this.
Thoughts and opinions welcome and thanks for having a read!
Regular pictures/updates on my instagram @danhargrave
The gearbox spline shaft, universal joint and about 2 inches after the joint are all steel. I can't imagine they would work very well if they were all carbon.... 
