My oldest son thought I have a little too much free time, so he helped me out a little. While pushing snow with my WD last winter he snapped a valve stem, which broke the #4 piston and sleeve. I know he's just the lucky guy who happened to be driving, but know he'll see this post & I want him to know that I know. Anyway the tractor's been using oil all along & is worn so I plan to go completely thru the engine while I'm at it. Any good tips are appreciated. I'd like to add a little more power while I've got it apart. Is there an after market camshaft that gives higher lift & duration available? Any other reasonable priced changes I could make to help out the power end? What's the best way of getting the sleeves out & replaced? Anything special to look out for, best place for parts, anything you wanna tell me I'll listen.