Anyone know how a 160 vs a 180 degree thermostat affect the performance on a 351m? I do remember reading something about how the temp affects atomization of the gas way back when but don't remember the ideal temp for it. I live in Austin, TX and the winter temp here is about 40 to 50 F and 90 to 100+ on the summer so I wanted something not too hot for the truck. I'm in the process of tunning the fuel injection on it (commander 950 pro) and it feels like an oven in the cab cause the engine gets up to about 225. Maybe my thermostat is bad so I decided to get a 180 and try it out but now I'm thinking about a 160 degree. Anyway, just thought I'd ask. Thanks for any input.......................


AC

 

The thermostat for best engine wear and economy is a 192-5°F thermostat for the 400. Newer engines with more advanced cooling systems even use higher temp stats.

Your max engine temp will depend on your cooling system condition, radiator, scale, rust, etc.

As the engine temp decreases the rate of engine wear increases. Going from 180°F to 160°F QUADRUPLES the rate of engine wear and also increases fuel consumption per HP produced.

You can produce more HP with a cold engine but it requires a large fuel increase.

Always use the Cooper-Robertshaw brand thermostats designed for the 335 series engines.

 

Man, didn't think about engine wear! So how does temp correlate to engine wear? So does that mean that there is a thin line between ideal temp and overheating? As I mentioned before, my engine is currently running at about 225. How will this temp affect the engine? Wont it break down the oil much faster? Thanks for the info....

 

There is a chemical reaction that occurs at the combustion chamber walls from incompletely burned hydrocarbons. The acids formed eat away at the cast iron releasing particles of iron into the engine. These are picked up in the oil and circulated thru the engine which grind away at other parts making more particles. The lower the temp the more acids are formed. You can see visual examples of this by examining inline six engines. The cylinder wear is greatest on the #1 cylinder and diminishes as you go towards the back of the engine.

The filter only catches a certain % of particles that pass thru it. A fact that is widely unknown and misunderstood by most people. Filters are rated by something called a "beta ratio" at a certain particle size. Unfortunately you can't find those numbers for automotive filters. You can find them for industrial filters. Even then marketing messes with the figures to make them look better, -typical!

Check with the oil forum for oil breakdown information. It has been discussed there frequently.

Make sure your cooling system is clean (radiator and engine scale) and your thermostat is the correct one for a 335 series engine.

225 isn't a bad engine temp. If it is getting hot in slow traffic check your radiator shroud and fan clutch. At speeds under 35-40 MPH the fan draws air thru the radiator. At higher vehicle speeds air is forced thru the radiator by vehicle motion. Remember engine temp gages are not the most accurate things in the world also. Your cab getting hot could be caused by the heater valve not shutting off completely. Incorrect ignition timing can also cause an engine to run hot.

 

A new engine will tend to run hot until it gets broken in. So if you have a newly rebuilt motor, don't get too concerned about 225 degrees until you get some miles on it. Some shops use large fans to keep a new motor cool while they break in the cam etc.

 

Unbelievable how much goes on in an engine to get it going! All the science and physics going on and never thought about it. All I could think of was mainly the mechanicals when I thought of an engine. Very interesting guys.

About the engine, The previous owner said he ran the engine with a carb for about 7 to 10K miles before he parked it to work on the body. As far as the radiator it looks like the it has been cleaned out. I took a look in it and it looked very clean. The coolant was very clean. As far as I can tell the previous owner was doing a very good job at getting one thing done at a time. I will post the picks he sent me in a few minutes if you want to check out the truck. It still needs alot of things done before it is running again but it has been fun working on it.

AC

 

I wonder if you've got something else going on. With 351M/400's lots of guys remove disconnect the EGR. That would cause the engine to knock, so they retard the timing to compensate. That would cause low speed ignition to be late, maybe late enough to be partially happening in the exhaust system. That would account for the high underhood temperatures.

Did you truck have the EGR removed? If so, you'll need to fix the distributor.

 

Ive been told that engines should run about 180 degrees. That seems a bit low to me. I'm running a 200 degree thermo and it runs between 185-210. I bought a fail safe 180, but I still not comfortable with what temp I should run at. I was told by to engine guys that 200 or more makes them nervous, but they don't know crap about clevelands, just chevies (ick!!!). Is a cooper-robertshaw a necisary thermo. The ones Iv'e been using all have the thing that protrudes down to the bypass, but I'm not sure exactly by how much or if it the proper one. A part number would be best, if anyone has one. Thanx.

 

http://www.flowkooler.com/thermos.php?pid=TS333

 

Kopfenjager-
Your temps sound fine. The OEM stat for a 400 should be 192-195°F. I wish I had the Cooper Robertshaw number for you. Use the generation-2 or the Extra Performance thermostat. They used to be available from Auto Zone but I have no idea if they still are.
Check out this link:
http://www.cooperstandard.com/us/en/...Thermostat.asp

 

acid build up is part of it but the other is cylinder wear because the aluminum pistons heat up faster than the cast iron walls. which causes lots of friction.

 

Cool I have a 333-195 thermo in it already. I went through this awhile ago and bought one. I thought it seemed like a familiar topic! I just spaced it and started second guesing myself. Thanx guys

 

I put in a 160, truck isn't driven much, need ins on it. I may go up to a 180 later, but my fan shroud busted and locating another is impossible around here, I may make one from metal, then I'll bump the thermostat up. I have a factory fan setup, but no clutch, thinking of replacing it with a flex fan, since I have no shroud, I may try to upgrade to a little larger fan to form a shroud around or go with electric fans. I always look for Robert Shaw stats, so you say a minimum of 180, maybe higher, will this not cause pinging or overheating?

 

Use the factory shroud, they are available, and the OEM clutch fan setup. Use the OEM termostat temp of 192-5°F. No pinging unless your distributor is not set up properly. Forget the flex fans. Forget the electrics unless you drive in deep water so you can shut them off. Otherwise they are not nearly as reliable as the clutch fan. They will save some HP in a race application but in a daily driver they are not nearly as efficient as the mechanical clutch setup.

-Just my 2¢

 

My truck for some reason had no flex on it, it's got the stock BS, still on the shroud search. What year truck are you driving that has a fan clutch?