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Circa 1970s 318 t-stat temps

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billm2

New member
I've seen many posts about temps for 318s but with conflicting recommendations. My twin 318s have seemingly 160 t-stats in them. The engines are raw wTer cooled and I run in fresh water with an occasional trip to salt waters for a couple of weeks. The engines are 1970s vintage. What t- stat should I be using, keeping in mind the gauges show them running at around 170 at idle? Also, would like the correct Sierra or Napa part number.

Many thanks!
 
The manual states "140 to 165 degrees for raw water system and 160 to 200 degrees for fresh water system cooling." So 140 stat is the correct one here especially if you're doing any salt water boating.
 
Info is direct from Chrysler 318 manual. 140 to 160 degrees is what you may realistically expect a 140 to run at. Note that the upper end stops at the point which crystalization may start to occur.
 
WoodieMan said:
Info is direct from Chrysler 318 manual. 140 to 160 degrees is what you may realistically expect a 140 to run at. Note that the upper end stops at the point which crystalization may start to occur.
Click to expand...

Thanks again. You're referring to salt crystallization, correct? I run in fresh water but will also periodically run in sea water. I would think that crystallization would be nominal particularly since I would return to fresh waters - up the Hudson from Long Island.
 
Correct on the salt crystalization. Jeff also brings up a good point in the link you posted. Read post number four there.
 
Sure. There's about 6 to 8 pounds back pressure in the block above 3,000 rpms, dropping to barely a pound at idle speed. That's not enough pressure to prevent water in the block from steaming after a hot run; and steam doesn't cool the block and heads! Keeping the temp at 140 for RWC engines (per factory specs) prevents steaming from happening.

FWC engines develop 7 or more pounds pressure since it's a closed cooling system--including idle--so it can be run hotter.

Jeff
 
Thanks very much Jeff for your answer and joining this thread. Now I guess my question is which part is the correct stat for my engines. According to this part sheet, there's a 140 stat for all V8s in the year range of my engines (my engines's serial numbers indicates they were made between 1970 and 1974) and a 140 stat for LM 318s which are my engines. The price difference per stat is some $60 to $70. See stat part chart here:

http://www.marineparts.com/partspages/Chrysler/chrysler7.htm
 
Outrageously $$ aren't they! If you're mechanically handy, you can make a stainless (or galvanizxed) plate to adapt the more common and cheaper t-stats. (The correct one is much larger in diameter.) I epoxy and pop rivet the smaller, cheaper t-stats to this plate and use double gaskets to install it. Works great!

Jeff
 
Well, I finally my LM 318 engine manual which states vaguely that a raw water cooled engine as well as the fresh water engine should have either 160 or 180 degree t-stats. No mention of a 140 anywhere in the manual which is the same vintage as the engines: 1970 - 74. How's that for throwing a wrench into this....! Guess then, the tech writers didn't have an Internet connection.
 
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