So I'm at the crossroad to fix my '91 300E with a broken valve spring (exhaust #4 cyl.) I'm going to scope the inside cyl and make sure that the valve and piston are not damaged. If there is no noticable damage then I'll change out the spring and lifter.

I'm not planning on taking the head out to change the valve and reseat it since I just had the head redone (new guides and seals) about 20,000 miles ago.

Has anyone done this before? Any issues with burning the exhaust valve? or if there is a pit on the piston then would it cause predetonation or carbon buildup?

Any recommendations or previous experience would be appreciated.