Thanks Jim, I have looked over this info before and it gives me a good idea for the stock engine. Not really sure if there is any difference between a 27r45 and a 197r45 other that the distributers. Axe with the 27r45 and SG with the 197r45. Any how i am really wanting to know what kind of performance gains the vp mod will give the engine. I can not find any info on rpm/prop number with the vp mod. So i was hoping somebody might have some experience with the vp mod.