440 big bore gone wrong.

[Bigpoppa]

Hello my name is mark I'm new to the forum and am looking for good advise. this weekend I bought a mint 04 400ex dirt cheap. I bought it cheap cuz the p/o had a 440 big bore put in in but suddenly lost compression. I tore it down to find a bad t-chain tensioner and both intake valves bent.I've built several engines before and I'm a professional wrench. my question is do I rebuild it back to a 440 which I was told is not so reliable or start over with a 416 or 426 kit. I don't race quads I'm looking to build a trail beast.

[headache]

I'd keep the 440. does it have the larger head studs installed? If not i recommend doing that and throw in some fresh valves and timing chain and tensioner and youll be good to go.