Ok, I'll jump in here. My car had a CB Performance 1915 with some mystery head work (Pat Down didn't tell me what he'd done) that ran well for 56k miles before I sold it on. It was coupled to a Rancho Pro-Street transaxle with a 3.88 R&P. Quick and responsive in traffic it would cruise for hours on the expressway at 80 even though that was 4000 RPM. While the Weber carbs were my nemesis for a while, the rest of it was pretty low maintenance. One point I'm hoping to make is that it isn't just displacement that matters. When my car was built Beck offered two different 1915 engines - one was a tame, low maintenance 90hp model and the other was a higher performance 125hp (like mine) that was capable of being souped up further. While I can't vouch for the power rating, it was a strong engine that was quite happy at higher RPMs for long stretches.