Ok, let's start off by saying I found out at the end of January that I probably jumped the gun to the tune of nearly $500, and about 6 hours of machining time.
When I last made an adapter plate/flywheel spacer combo, I had a full cad model, including clutch and pressure plate, transmission (with input shaft), engine crank surface, release bearing, clutch fork, pivot ball, and everything was verified to work before anything started.
This time I neglected to check the throw on the release bearing, the protrusion of the input shaft, and a host of other things.
I think I was a bit blinded by the "happy happy!" of finding out the ring gears matched, and didn't check the big picture and big issue items.
In my zeal to get things finalized, I generalized that if the ring gear worked great, then I'd be able to use an aftermarket off the shelf flywheel, with only a spacer to adjust for the adapter plate thickness...
Cue ordering a $378 flywheel, $58 pressure plate, and $48 clutch disc, and machining up the following adapter.
Final touches, had a bad dimension for the depth of the counterbore that locates on the counterweight.
I had it as 2mm on the print, should have been 3.5mm. Easy enough to fix.
M10x1x35mm flange bolts, to replace the 20mm ones that came with the flywheel. With the 13mm spacer they fit great, and didn't hit the rear stationary gear bolt heads. You can also see the locating lip for the flywheel.
The counterweight side, with 77.86mm diameter counterbore and lead-in chamfer.
Setting on the flywheel, before being pressed in.
Pressed in, ready to mount.
Mounted down.
Side shot
The clutch disc and the pressure plate came in back on the 29th, so after work I popped out to the shop and started the shenanigans that informed me of my possible major screwup.
Oddly enough, I was sent a sprung disc for a different Nissan by accident, but it turned out to be the same price, same dimensions/splines, and sprung, so meh.
I turned down the transmission centering shaft to also act as a clutch alignment tool.
I stopped taking pictures after that, since they were going to be near identical to the flywheel install ones already shown.
It was after bolting the pressure plate and clutch onto the flywheel and setting the transmission back on, that I noticed I had no release bearing engagement.
That's when the penny dropped, and I swapped the alignment shaft for the input shaft (it's bagged along with the other guts to keep the case more manageable...), and confirmed I only had about 1/2" of spline engagement into the clutch disc.
When I removed the 1/2" bar stock spacers that are currently standing in for the adapter plate, I could get about 7/16" of engaged travel on the release bearing before the clutch fork bottomed out on the transmission case, and I had about an inch of spline engagement.
It turns out that while the Sentra flywheel may have the ring gear in the same ballpark location as the 13B, since it is a dual mass unit the clutch surface is quite a bit further out. From looking at the stock flywheel photos and scaling from known dimensions, it seems to be someplace between 12 and 19mm from top of ring gear to the clutch surface.
This means I'm going to need at least another 12mm of spacer, which puts me to 25mm on the low side. That means I'd need 45mm long bolts, witch is a little bit on the long side.
This has been gnawing at my brain since the 30th.
I'm torn between two options:
1: Buy a Sentra aftermarket steel flywheel/clutch/pp kit, and make an adapter to bolt it to the Wankel, and sell the flywheel/pp I bought.
2: Machine up the 25mm adapter, and see if I can get out of the pickle I got myself into.
Option 2 is cheaper money wise, since I have the stock, have the flywheel and pressure plate, and know where I went wrong.
The longer bolts have me worried, but I may be able to use press-in studs.
Option 1 brings a bit more uncertainty as to whether I can physically make the adapter, but then I know the rest of the clutch/starter/pp/release bearing will work properly.
I'm leaning towards option 1, but I'm unsure.