Just completed a top end overhaul on our Perkins 4108, head jetted,  new head gasket, springs, valves, seats cut, gaskets . Cost for parts and seat cutting/jetting was $550cnd +\- just for the top end. Without checking the rpm off the crank I’ve gotten back my max rpm and smoothed it out substantially. When checked before I maxed out around 2600rpm, now back to above 3k (will conform actually with handheld tach later if anyone’s interested) The seats were slightly pitted and carbon on valves and pistons at 4400hrs. I did do several other upgrades at this time but nothing that would effect rpm and operability. Also noticed less smoke after initial start (more at start as I replaced all fuel lines throughout, and bleeding/starting was a bear and there was quit a bit of fuel in the cylinders when it finally fired) 

In addition to the top end I replaced the starter with a new smaller, faster and most importantly lighter starter as well as a serpentine pulley kit, spreader ring for the timing cover (no more oval washers), front seal, SS exhaust riser, new hoses throughout, Balmar 6 alternator with MC and duo charge controllers, new fuel lines, new oil lines strip and paint all removed parts. Parts came from both TAD and Parts4engines, no problem from either supplier with fit or install. To finish it off I still have to install k&n air filter (I have one on board and just can’t find it) and new battery cables throughout the system.