Lately I've been reading, "HOW TO REBUILD BIG-BLOCK FORD ENGINES," by Steve Christ. Here are the front and back covers of the book, in case any of you aren't familiar with it (you can click on these images for large editions):
Page 72 features a graph that I found absolutely fascinating (click on it for a larger view):
I scanned through the surrounding pages but couldn't find any detailed explanation of the graph in the book--yet I suppose it's self-explanatory. But is it true!?
If this is the case, then it really reveals the folly of those who remove their thermostats, thinking "the cooler the better."
Also, Tom Lucas (my new engine builder) recommended that I use a 160 degree thermostat, which should keep the engine between 165 and 170 degrees. 165-170 looks OK in this graph, but it still makes me curious about how accurate the graph is.
Is the information presented in this graph accurate?
Thanks very much for the absolutely fantastic advice!
Robroy
Robroy, Google, "increased engine wear below 160 degrees" and read up. There are several references to the increase of wear at lower temps. Some of the links even have a graph similar to the one depicted in your post. I would never run a T-stat lower than 180*.
Good question. I do not have an answer but Tom did put a 160 degree thermostat in my FE 410. I live in Sacramento and it gets over 100 F in the summer with very low humidity. The engine runs around 160 to 165 in the winter (based on me eyeballing the gage when the thermostat opens). The engine runs a little hotter than that in the summer when I am sitting in traffic but no where near where it was running before. I had intended to remove the tire from the front to allow more air flow but operating temperature has been good so far. I had the C6 rebuilt over a year ago and added a transmission fluid cooler directly in the air flow. The old one was on the fender. The transmission runs much cooler now as well.
69 F250, FE Specialties 410, CJ Valves, RPM Intake, Holley 4150,......10 Smiles per gallon
71 Clydesdale in many pieces; 302 roller motor waiting impatiently
I remember the recommendation about the 160` in the other thread. From the engineers, combustion efficiency is a lot better the hotter an engine runs. I think I remember the Indy cars were running over 300` coolant temps.
I'm not sure how the temp corralates to cylinder wear, or really why it would wear differently. The piston and ring package temp should be pretty constant and the iron won't have expanded as much at 160 vs. 180. I know my 302's run better at 195 vs. 180 but they are EFI
I don't know about cylinder wear at lower temps, but especially on heavy-duty diesel engines, there is definitely more damage done to cylinders at lower temps.
The reason for this is cavitation.
Heavy-duty diesel engines have cylinder liners, rather than having direct contact between the pistons and the block. This allows for engines to be rebuilt countless times without having to do machine work on the block itself. If the cylinder has excessive wear or damage, replace the liner and the piston, and you've basically got a "new-from-the-factory" cylinder.
There are, essentially, three types of configurations. There is the wet liner, where o-rings are used in the actual bores in the block to seal against the liners, and the liners are surrounded by water at all times. Second is the dry liner, where the block is completely sealed from the liner, and cooling takes place through heat transfer from the liner to the water-cooled block. No water ever contacts the liner itself, thus the name. Third is basically a hybrid of the first two, known as a wet-and-dry liner. The upper portion of the liner is cooled by direct contact of the coolant with the liner and the bottom portion is kept dry.
Cavitation occurs on both the first and third types, where coolant is in direct contact with the liner.
Basically, at lower temps, the friction created by the rings and pistons while moving up and down in the cylinder create an electrostatic charge on the outside of the cylinder liners. This electrostatic charge attracts air bubbles that attach themselves to the outside of the liner. As the cylinder temperature increases, these air bubbles implode on the side of the liner, and the force is powerful enough to knock off small particles of metal from the outside of the liner. Over time, these implosions can remove enough metal to actually penetrate the liner and allow coolant to leak through into the cylinder, and in extreme cases, compression can pass through these penetrations and over-pressurize the cooling system.
I've actually seen liners pulled from engines that had areas the size of a dime that were paper-thin because of this.
Consider the following:
* This happens while the engine is cold, and is more pronounced when the engine is revved while cold. That is one of the reasons for leaving diesel engines idling in very cold temps, rather than shutting them down while the trucks are parked.
* Maintaining proper coolant mix helps to minimize this condition, as proper coolant is less prone to aeration.
* Special chemical additives are used in heavy-duty diesel engines that are designed to coat the inside surfaces of the cooling system and help prevent cavitation from occurring.
* A bad engine ground to the electrical system can greatly exacerbate the condition.
* The same phenomenon can occur in gasoline engines, just not to the same degree.
With this in mind, make sure you have a thermostat in your engine that will bring it up to normal operating temperature as quickly as possible. Maintain at least a 50/50 ratio in your cooling system (60/40 is the optimum mix for cooling protection as well as boil-over protection). Replace your coolant annually, as the additives in coolant DO wear out, just as they do in motor oil. Never unnecessarily rev your engine at cold temps.
Wise men talk because they have something to say; fools talk because they have to say something.--Plato
Why is it that there's seldom time to fix it right the first time, but there's always time to fix it right the second time???
That's not an oil leakThat's SWEATfrom all thatHORSEPOWER!!
That's interesting. I always heard and read theat cavitation was caused by the diesels compression / ignition / explosion pulse. The '95 factory turbo'd IH 7.3 I pulled apart a couple years ago had a ton of pin holes around the top 1" of all the cylinders and I understood that happens because IH's poorly engineered block. The Cummins with the thicker cylinder walls doesn't do it and also needs about half the cooling capacity as the IH motor. The thinner walls flex more and transfer too much heat to the coolant.
If one considers that Continental made (makes?) aviation engines I'm sure they could make them run cold at altitude if they wanted but I wonder how much wear was caused by the rich mixture needed to keep them running that cold?
Jamie
Ranchero50 wrote:That's interesting. I always heard and read theat cavitation was caused by the diesels compression / ignition / explosion pulse. The '95 factory turbo'd IH 7.3 I pulled apart a couple years ago had a ton of pin holes around the top 1" of all the cylinders and I understood that happens because IH's poorly engineered block. The Cummins with the thicker cylinder walls doesn't do it and also needs about half the cooling capacity as the IH motor. The thinner walls flex more and transfer too much heat to the coolant.
Jamie
Correct.
This compression/ignition/explosion pulse is the source of the electrostatic charge. The electrostatic charge is what causes the bubbles to "adhere" to the cylinder walls. The heat generated by the compression and ignition of the fuel is what super-heats these bubbles.
Now, keep in mind that I was discussing HEAVY-DUTY engines, not the IH and Cummins engines used in the light-duty trucks. My experience with these lighter-duty engines is limited to the 6.9 and 7.3, as I worked several years at an IH/Navistar dealer. I did very little work on these, however, as my area of expertise was with the larger engines (Detroit, Cummins, Cat).
Cummins is probably the most-affected of all of the engines I've worked on, and the cavitation can and will occur anywhere that the rings contact the liner in these larger engines.
Wise men talk because they have something to say; fools talk because they have to say something.--Plato
Why is it that there's seldom time to fix it right the first time, but there's always time to fix it right the second time???
That's not an oil leakThat's SWEATfrom all thatHORSEPOWER!!
Look inside of a late model engine..not uncommon to see not much cylinder wear at 100k. Higher operating temp equals lower emissions, better fuel economy & less wear. The 302 in my 69 & the 46 both run 195 t-stats. Both have large radiators, t-bird cooling fans. The 46, with the air on runs about 200-205 in traffic. The 69 (no air yet) runs 200...
Besids, to burn the crap that passes for fuel these days, you need heat in the holes.
as always...
As a metter of fact, i AM trying to keep up with the Jones'
Driving like Parnelli, Drinkin' like George
-------------------------------------------------------
"Beauty is only skin deep....Ugly is to the bone"
It is more important to understand what you don't know than what you do know,because then you can start to learn..???
"you must deal with the attaboys and the ass chewing s with your head up and looking them in the eyes" T.J.E. aka My Dad
There are only three types of people wolves, sheepdogs, and sheep. What are you?
Robroy, that 160F thermostat bothered me right from the first time I
read it but, with what all was going on, I hadn't mentioned it.
Print that graph out and ask Tom about it for us. :)
Let's hear his side of this thing. :)
I lived in Suckmytoe for almost 3 years and in an old car had the 160F
thermostat in it and milky oil ended up on the top of the dip stick! :/
Yep, switched back to a 180F and it went away. The 160F didn't do that
in AZ but even as dry as 69 thinks it is there, it's still wet from my point
of view. LOL :)
So is that another source of engine wear?
Ivory Liquid instead of engine oil, a good thing? ;)
Seems to me it's even wetter than Sacto, where you are. :/
I'd like to get to the bottom of this issue and I figure you are the one
to do that for me, Rob"pitbull"Roy. Go get 'em. Sik 'em! LOL :)
Tom, look out! ;) (you went and stepped in it yourself tho)
Well for part of the answer do a compression test when your engine is cold and another one when the engine is hot. Chances are when fully warmed up the compression will be higher becuase the rings seat better, the oil is nicely coating everything, and all of the seals are fully expanded. Also in a carb'd engine until the engine is fully warmed it tends to run rather rich which contaminates the oil especially the oil coating the cylinder wall which leads to increased wear.
As far as temps I am inclined to go with the higher is better arguement. The hotter a fire the more complete the combustion and it also does a better job of turning the water vapor into steam which is easier on your exhaust.
On the milky oil in certain areas this is generally caused by water getting trapped in your oil. A good half hour to hour drive will generally boil off the water.
Yes, wear goes up with lower temps. When an engine isn't running (especially a carb'd one), you get condensation. The condensation gets in the oil. So that is one problem. The second problem is, oil is designed to operate at a specific temp. It works the best at that temp.
So, the burn off the water and gas that gets in the oil, you need high temps. To get the oil to flow the way it should, you need high temps.
NOTE: if you are dealing with a race motor that is taken to the track, sees only WOT and you change the oil after every weekend, then yes, cooler is better (faster), but then again, you rebuild the motor after every season so really the motor only has maybe 100 miles on it. For a daily driver, that you want 100,000 miles out of it, you need at least 180 and I like 195F thermostats.
My 71 F100 runs a mild 460 with a taurus fan and plain FE radiator. I run the fan on high speed hook up to a switch to turn it on at 205 and turn it off at 195. I also have a 195 thermostat. On the highway (lots of air flow), the fan never comes on and the temp goes back and forth between 190 and 200F. Oil stays nice and hot so it can do its job and it also stays nice and clean. At that temp all the water and other junk boils off. When I am in traffic, the temp gets to 205 and the fan kicks on. The fan brings it back down to 195 and shuts off. Works great and I get quick heat in the winter but stay right at 195 in the summer.
If I can run a 195 thermostat south of houston with a 460, AC, and big headers, then anyone can.
I have pulled the valve covers off of an engine that ran a 160 degree thermostat and it is nasty under there. Nothing burns off and it just collects. SLUDGE!
