Well after working with my buddy Ron we got one of the old Italy ST 45s to turn a APC 9x8 at 17,400 with a tower muffler on 10% nitro and 18,100 on a red Jett muffler with 5% but needs a bigger chamber with the pipe. Runs really well with the Tower muffler. It has the lowest ports of all the Italy engines too it seems they were changing port sizes and heights over time.