No I don't think you can the piston rod and sleeve are different you go to to your lhs and trade your 2.5 in for the 2.5r it's $100.00 and you get a new 2.5R Race Engine or you can ship it to traxxas and do the same thing. Look at Traxxas .com for the life time engine replacement .I had the 2.5 and traded up for the 2.5R Race Engine and it just drops in and you can use your easy start with it or the pull start like I did I didn't like the easy start because it was difficult to get to the LSN and it added extra weight. But you can do what ever is easier and works better for you.