I had a Riva 46mm single carb manifold "kit" on one of my 62T motors and had a fun time trying to get it dialed in. It seemed to have about the same performance as the dual 44's that were on a R&D manifold (from 1/3 throttle and up), but the low speed (idle to 1/3 throttle) was the area of operation that I never got right. One of the issues was that the pop-off ended to be about 12psi, and with that low pop, the motor vibration (more or less,and frequency) at different RPM's would shake the needle from the seat and mess with my settings. The extra fuel consumption was probably because of this. The AM carbs some of you guys are running with higher pops might be less prone to this issue.
I sold the manifold, and bought another 46mm and made a set that (so far) meters more precise (higher pop-off) and offers better fuel economy. I really wanted to run a single for simplicity, but I couldn't get it to work right. For now I'm dealing with them (the duals).
