I recently had a 2.5SS motor built with the intention of running it with a stock 905/20 Sportomatic gearbox. Upon assembly and testing, the builder found that at peak torque between 5500-5700 rpm, the box couldn't handle the torque. He tried replacing the stock 905 pressure plate with a Kennedy performance plate but experienced the same issues. Upon disassembly he saw no harm done to the plate, so he's speculating that the torque converter might be the weak link.

We're now trying to figure out next steps. One option might be to use a 925/xx box in place of the 905/20; another might be to use just the torque converter from a 925/xx. A manual swap is out of the question because reasons, so please don't suggest it.

I'm aware there have been Sporto equipped cars out there that handled 2.7RS and 3.0SC levels of power, so I have to think that a properly prepared Sporto could handle the ~200ish hp from this short stroke motor. What I don't know is how to ensure the box is strong enough to handle that power. I know it's a long shot, but if anyone has any experience in this area (I've already cross-posted at the bird) I'm all ears. Thanks.