As it turns out, we are building two 1507's............one for a customer and one for me. Testing on the customer bike is pretty much done and the dyno results are linked below.
The first and lower pull was done with an exhaust cam and lobe centers that we had reservations about but did not want to over scavenge the cylinder with a bigger camshaft. The results from the first combination are OK but clearly below what we feel the potential of a 1507 might be.
There were several indications that there were bottlenecks on the exhaust side and that we were incurring pumping losses and losing VE. In the course of one day Bryan dropped the engine, reshimmed the head and installed a larger exhaust cam with a different centerline.
As can be seen, the results of this change is dramatic.............now making almost 240 HP. This is with a stock valve head, flat top pistons, sidewinder, MRX01 and 30 psi in the rear tire.
How do we evaluate this? Computer simulation models suggest 240 to 241. A couple of informed members have suggested 230 to 240 to be the capacity of a 1507. One member reported getting 238 from a 1507 built by a prominent engine builder.
Ina Dragbike.Com article Lee Shierts got 242.5 out of a big valve 1507 but we know his dyno reads differently than ours based upon results with almost stock bikes.
Probably the best measure, though, is comparing this 1507 with our very proven 1397's. We typically get 220 out of a 1397 and this works out to 157.5 HP per liter; using similar math with a 1507 that puts out 239, it works out to 158.6 per liter.
Thus, we are very satisfied with the combination and want to extend Jim of Competition CNC a special thanks for his assistance in designing and developing this package. We will post the results for my bike as they become available.
