My t-stat is 195. What is the normal temps for the truck? It’s a 78 d100. Right now it’s above 200

Sounds like you have something besides the stock gauge to tell that? How/where are you measuring this? How much over 200 is it? I put a new sending unit in mine, gauge was pegged as soon as I turned the key on before I started it, with the engine stone cold

The thermostat sets the engine's minimum operating temperature, not its maximum. Read this.

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Yes I put a aftermarket temp gauge in as well I have both now. I wanted to see if it was getting as hot as the original said it was and it’s not. The original gauge shows it runs hot, way to hot. But I don’t know how hot it’s really supposed to get before it’s a problem. Today it got to around 210 tops. I’ve done some more work to the engine lately and figure it was about time to update a few things and put some old things back on. Reinstalled the egr valve and fixed my dizzy vacuum lines. Now the timing is much better and doesn’t go beyond what I can see with my timing light like it used to. There’s still small issues but none that should contribute to a overheating engine.

Good read and makes more sense now. Thanks Dan.

Just how far does your timing light read too. The timing tab is only marked to 10*. The timing should at least go to 30* static. Excessively retarding the timing can lead to overheating issues.

Yup. As I did to my most recent build, it started pretty readily where I had statically set it up on buildup, so I "ran with it" for the initial run in while I monitored oil pressure and temp, and listened for potential bad things. Until I felt the blast of hot air on my arm from the fan blowing thru the radiator and shut it down. Once cooledi restarted it and dug out the timing light.

I like my dial back timing light, with that as long as the damper is (correctly) marked and there is a"0" reference on the engine I can read timing directly off of the back of the timing light

I typically run 195 tstat in my 225s. Less engine wear, better throttle response, usually. If I have a real hotrod motor, I'll run a 180 to protect against detonation. If you have a stock or moderately modified motor with a good cooling system, then I would run 195. This means the engine will settle in and run around 200-205 F.

Lou

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It’s just a standard timing light. Couldn’t read past where the tab was but it would go off the side. But all is well with that now after I added the egr back and reran the vac lines.