Originally Posted by
marksp
That's a lot of prop for the VVRC 40. Most run the 20x8 or 20x9...I run Xoar 20x8 which works very well, FYI.
That's what happens when half the quote is used. As described above, tuned pipes will be used on this mill as I do all of my gassies. For example my piped OS GT33 turns a 20.5x10 PN APC at 7000 (ground) which is about perfect for my application. Pipes boost torque and rpm. On the other hand it may turn out to have only the power of the 33; we'll see....
I agree that on regular muffler, a 20x8 to 20x10 is probably about right for the twin.