Frustrating day with the Porsche Trans, but I'll get it figured it out. I've read the various "how-to's" that are out there, but have found them to be somewhat lacking in details. Surely the Bug5atspeed products would make this quite a bit easier, but it's well outside the budget I have left to complete this. I'll try and detail out my solutions should someone in future be looking for threads on 901 installs.
Factory VW transmission (and, I believe, the Porsche 915) has some flat sections in the lower corners for the motor mount bolts. The 901 Porsche trans? No dice...
I've flipped the transmission upside down in this next shot to show the Beetle transmission mount on the Porsche Transmission...will need to adapt the beetle Urethane mounts to fit to the metal mount.
First up is removing this piece off the bell-housing. I suspect, but have no real idea, that it's for a clutch release spring. Regardless, it's in the way and gets removed. Didn't bother taking a photo of it all cleaned up, but basically you need to remove all the material from the rib to the bolt hole, leaving the lip around the bell housing like the rest of the transmission.
From there, it was onto modifying the Urethane mounts. This stuff flies everywhere with a carbide cutter, and melts and drips when you use a metal cut-off wheel. Sure hurts when it lands on a pant leg!
...and now the scary part. Drilling the case of a Porsche Transmission.
...eventually you end up with this, which isn't perfect. Ironically I can't seem to find a photo of anyone else's 901 install, so I'm not sure if other people run with the mounts stressed like this, or came up with an entirely different solution. I can't, however, leave it like this as I know it will fail prematurely. I'll have to pick up some sheet urethane and start working out a spacer-type solution. Ideally the urethane would run along the metal mount touching for the complete radius...but I don't think I can set it up for this to happen. It's really driving me nuts that I also won't have an "off the shelf" solution if the mounts fail or wear out.
Once I solve the mount shape issue, I'll have to then sort out the bolt-heads inside the bellhousing. The bolt heads interfere with the ring gear, so the common solution is countersunk allen head bolts. I'd like to see if I can come up with something a little stronger, but I'm not quite sure what yet. The current thought is a metal strip inside the bottom of the bellhousing, to which studs will be welded to. Need to talk to a buddy at the rally shop to see what he thinks.
-Dave