420C - Engine Questions

[CCWKen]

As I mentioned in another thread about building a FOPS, the head gasket blew and I couldn't see having it down that far and not check the valves. Well, good thing I did. I always though it was a pretty strong runner but apparently, it's been running on about 1 1/4 cylinders. One exhaust valve looked like it wasn't even closing on the seat. And the other three valves look well seated but the contact area looks way too wide.

The questions:
1. Are there supposed to be valve guide seals?
2. What's the suggested valve seat contact width?
3. What's the valve clearance?

I also found out it's been running with no thermostat. Probably not a problem down in this hot climate but if I decide to put one in, what's the temp? There's no excessive carbon build up so it's not running too cold. It's probably what saved the one exhaust valve from being cooked.

[notmeu]

Ken, I can help you out on the thermostat, 160 is what I have in mine. I'm pretty sure I looked into the recommended temp when I went thru my motor years ago. Tom

[CCWKen]

Thanks Tom! Even on the hottest day, I rarely see it run above ~180 so I doubt putting in a thermostat is going to make it run any cooler. Winter down here lasts for about 2-3 weeks split between December and January. Temps below freezing are pretty rare too. And if it were, I sure wouldn't be out tractoring. It's been running like that since I got it so maybe I'll just leave it out.

[mini kahuna]

I would put the proper thermostat in it, running without a thermostat, causes the coolant to circulate full bore all the time, this can actually cause "hot spots" in the engine cooling passages because the coolant is traveling so fast around the system it doesn't pickup any heat and remove to the radiator.
some engines are fine, some will suffer damage from prolonged use without thermostats.
seen a case 4 cylinder cummins with some weird wear at the bottom of it sleeves from running cold all the time.