I am looking for advice on what to replace ie: springs/ valves or headwork on my 02 merc 500 efi's that have a little over 400 hours on them. Last time out I started hearing some pinging and minor backfire upon takeoff from one motor so i put it back on the trailer. I know that they are common for breaking valve springs so I am looking for advice on what new ones to replace and where the best place to get them. Also if there are any minor upgrades to do while they are apart. Any info is greatly appreciated. thanks, Justin

New springs for sure..Check your fuel pressure on that pinging!!!!

Replace valve springs and have guides checked for wear and replace where necessary.

Also have the ports cleaned up and make sure to have the injectors flowed and replace any that are out of range.

Sounds like its time to freshen the top end. Jim valeko is really good with heads and works on Ryans 02 black thunder which is now running in the 80's!

any pics of your black thunder?

thanks for the input. does anyone have suggestion for what kind of springs or guides and where to purchase. I will try and post pic later.

Head gaskets are most likely gone too.

+1