Hp 500
 

I have 690 hours on 1996 HP 500s I do not know if the valve springs have been upgraded is there a easy way to tell?

If your engine is on its original build, it probably has had the springs replaced by now. 200 hours is the recommended life. You could go farther if it's been babied, but who does that? If they are the original springs the valve seat pressures are way out of spec and its probably not running well.The easiest way to tell if the valves are sealing well is to do a compression test or better yet a leak down test. But worn piston rings would have to be ruled out first. You could pop the valve covers off and look at the base of the springs for shims, if they are shimmed then those springs have to go. I've saw this from cheap rebuilds and is a no no in my book. I would put new springs on, it's just cheap insurance against a catastrophic failure.