OK, a couple of things, then. The rev limiter may be set to 6600 rpm, but that doesn't mean mean you can do that for any length of time without overheating or other bad things happening. What that time is I have no idea; could be a minute, could be 5 or 10 minutes. Next, the dyno data is, as I said above, for WOT at the rpm shown. In cruise you'll be at a much lower throttle setting so it won't be developing the HP the chart shows at that rpm.

OK. Looking at the chart from the chevy website, it looks like peak HP is at about 6000 rpm. Say you're using the 2.21 reduction, that puts the prop rpm at 2714. Even at zero airspeed, that puts your tip speed over Mach 1. Thus you can't use the full rpm or 480HP, you need to limit it to 4800rpm (2172 prop rpm), or you need to reduce your prop diameter to something like 75", either of which will give you a Mach 0.8 tip speed.

But consider that a 72" two blade prop is what you'd expect to see on a 65HP engine at 2300 rpm. You might end up with a wide 4 blader that looks like it belongs on a T-28.

Are others using this engine and if so, what parameters are they using? Where do the reduction ratios come from?

Classical propeller design is as follows:

1. Choose the propeller diameter for Mach 0.8 at the max HP rpm.

2. Pitch the propeller so the blade airfoil is at max L/D at the design airspeed (full throttle climb, or reduced power cruise, or a compromise).

3. Size the blade chord and/or choose the number of blades so the prop can absorb all the engine's power.

4. Analyze and/or test and iterate.

With a variable pitch prop and/or a redrive where you can choose the ratio, it gets more complicated, you need to do it at all the possible configurations to see which works the best.

Dana