What temperature thermostat to use?

[74beachtruck]

Hello, all. So I put some aftermarket gauges in my truck the other day and noticed water temp going up to 205 degrees just idling on a 60 degree day. At the same time noticed a leak at thermostat housing so went ahead and ordered a gasket and thermostat. Noticed there was a 160, 180, and 195 degree for the truck. Not knowing which one it used, ordered the 180 and noticed the one I replaced was a 195 which I believe now is what the truck originally came with. My question is...Will a 180 stat harm the engine in any way if it is suppose to use a 195? When the 180 stat comes up to temp and opens it immediately falls to 160-165 and stays there even while driving. (60 degree day) Could this be keeping the engine too cool? Engine is a '74 350 stock except has true dual exhaust, no smog pump assembly and EGR disabled. Thanks for all you guys help!

[VileZambonie]

Less BTU heat energy in combustion and for the heating system. Will it harm anything, not really but it also isn't offering you any advantages on a stock engine.

[74beachtruck]

Thanks, Vile. Yeah, guess I'll be dropping some coolant again in the near future and get the right t-stat in there.

[VileZambonie]

Put it on your end of summer to do list 

[ScottD]

when I bought my 85 with a 350 i noticed the temp gauge never moved, so I thought it was bad.  I went through the cooling system and decided to replace the thermostat and found out that i had a 160. Asked around and did some reading and found most recommended the 195.  I replaced it a found my temp gauge did work and also noticed the truck ran much better.  However, now the gauge shows its over 200 (assuming not calibrated) so it did scare me when I see it go that high.  However after 5 years with the 195 and never having and overheating issue, I realized gauge is just not accurate.  I have a mechanical fan, live in MN, and only drive it in the summer.  so, it worked fine for me.

[MIKE S]

Modern engines are designed to run at hotter temperatures. It also promotes the burning off of the moisture inside the engine to keep sludge from forming. If you have any computer sensors or thermal vacuum switches on your truck you need to use the 195. Otherwise they will not function correctly. EFE valve, EGR, TCC lockup are some of the systems.

[Stewart G Griffin]

when I bought my 85 with a 350 i noticed the temp gauge never moved, so I thought it was bad.  I went through the cooling system and decided to replace the thermostat and found out that i had a 160. Asked around and did some reading and found most recommended the 195.  I replaced it a found my temp gauge did work and also noticed the truck ran much better.  However, now the gauge shows its over 200 (assuming not calibrated) so it did scare me when I see it go that high.  However after 5 years with the 195 and never having and overheating issue, I realized gauge is just not accurate.  I have a mechanical fan, live in MN, and only drive it in the summer.  so, it worked fine for me.

Read:
http://www.madelectrical.com/workshop/water-temp-gauge.shtml

[74beachtruck]

Thanks, everyone for your input! It did have a TVS switch that was screwed into the thermostat housing and was connected to the EGR system by vacuum lines to the carb but was disabled along time ago. There was never really a difference in the way it ran after that. The engine has always been very cold natured even before this was done and tend to believe the overall concensus that it's better, at least for the stock engines, that it's better for them to run a little hotter than cooler. Should have researched the OE thermostat better before I replaced it but I was on a mission!  😀 Going back to the 195. Thanks again!