difference between 25hp and 30hp?

[breeze]

I have a '55 RDE 17 25hp, my friend just acquired a '56 RDE 18 30hp. According to the service manual they both have the same bore, stroke, cu/in displacement, and use the same spark plug. the gap on mine is 020, and his is 020. What is it that makes the 5hp gain?

We were just curious about what makes the change in HP. Thanks for any input that increased our knowledge on these great motors!

 

[spy1309]

Re: difference between 25hp and 30hp?

Piston shape, compression ratio and carburator used can have big impacts in identical engines so 5hp is nothing regarding your question.