So I've decided that my life wouldn't be complete if I simply put all this together and then was transmission-limited in terms of power. So I'm going the AR5 route. It also leaves way more room for the exhaust since it doesn't have a clutch fork.
A brand new AR5 transmission for a Solstice is just $600 (plus $300 shipping), which makes it a pretty attractive option.
Clutch choices are pretty limited, as in there are two options. In reading Solstice forums, it seems that people have had poor experiences with SPEC clutches. Or one guy said he did and it became legend. Either way, no rave reviews and some bad reviews. So the only other option is DDM, which seems a pretty good option other than the fact it's $1100 for the cluch/flywheel combo.
Ecotec Miata has a coming soon AR5 install kit that includes everything but the drive shaft, which I'll get custom made.
All that together, and I should be good for ~375whp/400wtq if the internet forumz are to be believed. Anything remotely close to that and I'll be a happy camper.

I've still got to wait until December before I can pull the engine out, but I should be able to tiptoe my way closer by piecing all this stuff together.

Swap kits are available now ;)

Yes, insofaras I bought one. But it doesn't have a drive shaft and it's not on their site. But yeah, I wouldn't attempt this without a kit.

Buy a stock clutch and take it to a local clutch rebuilder to have the pressure plate resprung stronger. That's a good solution.

That's an interesting idea. The stock clutch can reportedly hold about 250 ft-lbs, so I'd want to achieve about 50% more holding power. Is there a parallel for Miatas? If that was a good, affordable option, why wouldn't it be a go-to for people running low boost turbo Miatas?

It would be if they thought of it or knew about a local clutch shop. Most people just buy them from the store because they are unaware such shops exist. Local clutch shops can reline your clutch disc, respring it if it has springs, and rebuild your pressure plate and respring it to hold a higher torque. I really enjoyed my ACT clutch that used a gently engaging stockish clutch material paired with a really strong pressure plate. It held a lot of torque. Adding 50% more clamping Force does not add 50% more clutch effort, either. It depends upon the lever ratio of the diaphragm arms.

We have clutches and pressure plates rebuilt locally all the time for work. And the shop we use does a lot of race car clutches as well as heavy truck.

The only real progress to report is that I've properly depowered my steering rack and ripped out the AC, since I won't be keeping those post-swap. I love the feel of the depowered rack, I'm not sure why I waited this long.

I also got a pile more parts. I bit the bullet and bought a clutch and flywheel kit from DDM. Since I would have had to buy a flywheel either way, and this setup uses a different flywheel setup, I figured I'd just spend the money and do it all at once. It's rated to 450ft-lbs, so it should serve my purposes. I also got a new AR5 transmission. I waited for a 15% off sale on eBay and picked it up for $500 (plus $300 for shipping :-O ). The internet says these transmissions feel kind of crappy, but are much improved with this short shift kit so I got one of those from DDM as well.

https://cimg3.ibsrv.net/gimg/www.mia...6ff580fdc4.jpg

Still twiddling my thumbs until I can get the car smogged in December. I'll be running with the stock engine at M@WRLS, going slow, and driving poorly.

Better than sitting on stands waiting for things.

Alright, I'm starting to work on this again. My goal is to have it running by January 1 (no year specified).

What I'm working on now is the drive shaft. The Solstice uses an odd type output shaft flange with no known off-the-shelf part that bolts up to it.

https://cimg9.ibsrv.net/gimg/www.mia...9b4a13366a.jpg


That leaves me with two main options:
1. use an adapter, such as the one from Drift Motion
2. Remove the flange entirely and find a slip yoke that fits

I'm inclined towards option 2, not only because that adapter will cost $140, but also the adapter option leaves no room for play in the drive shaft. I'd have to get the measurements exactly right, it would leave less room for adjustment in the diff and engine/transmission angle, and I feel like it would put unnecessary stress on the transmission and diff. All of those could be address by adding a slip join to the driveshaft, but that again adds cost.

I didn't have a puller on hand so I whipped one up with stuff I had laying around.

https://cimg6.ibsrv.net/gimg/www.mia...a2a29fe520.jpg

And with the flange off, I can see that it's missing an inch or so of spline, which means if I went with the yoke option, I could have as much as an inch of play without losing strength over the flange option.

https://cimg3.ibsrv.net/gimg/www.mia...e2e69eb4b4.jpg

My next step is to try and find a yoke that has the same outer diameter so that the seals that are already in place will continue to work. It appears to be a standard size with a 1.5 inch diameter.

An alternative option would be to essentially use this part as a yoke by not bolting it in place and fixing it to the driveshaft. I'll save that as a last resort as I imagine it won't be as strong of an interface if it's backed off even a little from being fully pushed in.

Does anyone happen to know if there is an off-the-shelf 1350 series flange for a driveshaft that bolts to the stock diff?

The standard yoke that fits the spline has a 1.5-inch outer diameter rather than 1.575 that the Solstice flange has. I found a seal from a 1984 Toyota Pickup which has the proper OD, and the ID is 1.495. It fits both the transmission and the new yoke, although creates a little resistance when turning. I imagine that resistance will go away when the transmission is full of fluid. Can someone correct me if I'm wrong there?

So, this kinda concerns me. Could you possibly take the yoke to have someone machine a few thosandths off to fit the seal. It would need to be polished too. Perhaps you can fill it with oil and see if it spins more freely, but I doubt it will.
Sorry I don't have anything more positive to suggest.

I tested it with oil, and it's still got some resistance. I think I need to find a different seal, or failing that, take the yoke down as you suggest.

Those lip seals are pretty common. I will have a look around and see if I can come up with one for you as well. I actually used to have one of those Toyota trucks, was my old work truck.

Okay, I'm bailing on the "turn the output shaft and a yoke into a slip joint" plan. The AR5 takes a metric sized seal, so there is literally no seal that has the right metric OD and also the right imperial ID to fit a 27 spline slip yoke. I could have it machined down to fit a metric seal, but there are so many ways in which this plan is far-fetched that I'm going to skip the innovation attempt, and go with a proven method.

Instead, I picked up this Drift Motion flange adapter. It adapts the AR5 output flange to mate with a standard u-bolt flange. From there ordering a driveshaft will be easy.

Today I got the engine and transmission mated together, and dropped them in for a test fit and to measure for the driveshaft. It fits!

Awesome result Nigel!

Driving by wrls 2019? :D

Most definitely. I'll be set up to do rides :skid: