Question Re Operating Temperature

[baypally208]

Question...

What should the proper operating temperature range be for water and oil temps on a SPF w/Oil Cooler and a 351 380HP Ford Racing Engine? Figure that the outside temp is about 98deg F.

Thx for the help guys!

-AP

[Bill Wells]

AP..you will probably get different answers.

remember, the spfs have a great cooling system with their puller fans and full shroud, so ideally you want to compare replys with other spf owners so you have apples to apples.

my original pre blower 351 crate was same as yours and would vary depending on outside ambient temps. water temp was misleading as the auto fans would come on at 90-92 degrees C and maintain the temps at that range as a max when ambient temps were in the 90s F. water temp would on rare occasion rise to 95-98 C degrees +/- in slow traffic but would immediately drop to 90 +/- C when fans ran or once traffic broke and i got about 1/4 mile at a speed of at least 30 mph. at highway speeds (over 55 mph) , with ambient temps in 85-95F range my water temp was always in the low-mid 80 c range +/-. Oil temps in traffic were about the same as water temps, but at hiway speeds the oil temps would run 5-10 degrees cooler than water temps. on rare occasion the oil temps would reach 100 degrees C when water temps were at the 90-92 Degree C range, (fan controlled).

car ran slightly hotter with the paxton but not considerably more.

after i blew the 351 and put in a 392 stroker the water temps ran hotter quicker and oil was usually too cool in colder weather, so i disconnected the oil cooler. now i run 90-92 degrees C water temps over 85 degrees F ambient with oil temps running the same or slightly hotter than water temps.

the fans really work great keeping the water temp down. for safety sake though, i added a manual fan override switch should my auto fans fail, as it did twice when i had a stuck relay. i replaced the fan relay and no more problems but the override is there should i need it.

bill

[baypally208]

Hey Bill...

We got on it in about 100 degree weather and the temps both ( oil and H2O) climbed up to about 100 degrees C. I'll drive it some more but that got me worried...

So provided it runs cool hereafter then no problem?

-AP

[Bill Wells]

AP, sounds like you had unusual conditions..two things you can do for those times of extreme high outside temps that affect engine temps as well :

1. add a manual fan override switch and when you see the temps start to rise quicker than normal due to higher ambient outside temps, turn the fans on manually before they come on automatically thereby getting the hot under hood engine bay temps pushing out those front fender vents quicker and for a longer period of time. i use my manual switch on occasion during the woodward ave dream cruise (read crawl) or during extreme high outside temps, which are infrequent in motown compared to other locales .

2. some folks add rubber to the bottom of the two levers that lock your hood closed, maybe 1/2 or 3/4 inch. ie, the two flat pieces that normally catch / lock under the fixed plates in the engine bay. then you can turn the levers so that when the hood is closed the rubber sits on top of the two plates mounted on the body, thereby creating a wedge opening effect at the back ( winshield side) of the hood. ie, you are not locking the hood then, but creating an opening. this allows considerable hot air out of the engine bay as it escapes thru the created venting . the hood sits up near the windshield 1/2 inch or so. some folks have designed a rubber or some other material wedge to put between the body and the hood . these are usually used by folks who do parade driving or have heavy traffic/ slow moving traffic/frequent high outside temps.

remember , these gauges aren't always 100% accurate either, and i find they tend to read on the 'high side', ie, 100 degrees C on the gauge is perhaps 97-98 C in actuality. you can take various engine location heat readings using the $100 or so infra red heat guns to see what various parts of your engine are temp wise. also, remember, the typical 50/50 anti freeze/ water ratio provides a boiling temp of about 235 degrees F, so 100 degrees C = 212 degrees F (normal boiling temp w/o antifreeze or other additives) . therefor you still have a margin of error. the oil reading being 100-105 C is not as critical as your water temps being near the 235 degree F range reading.

if your engine is unique and it runs hotter than similar counterpart engines, there are also some water additive products that reduce the water temps by 8-12 degrees F...one is Redline Water Wetter and another that reduces the temps more is a DUI product ( not sure on the exact product name...partialzheimers setting in, old age moment). both are used by lots of the racer folks and are good for street use. check your local performance auto supply stores or online.

if it aint puking fluid, it is not too hot is one way to look at it. sounds like your temps are ok except for extreme conditions that you do not regularly encounter.

keep cool. bill

[Jack21]

Modern engines, and their components are designed to run hot to vaporize fuel, burn fuel, operate at optimum clearances, and burn off engine contaminants. Typically, this is in the 180 - 205 deg. (f) range.

A 180 deg thermostat is full open at 180 deg. This sets the minimum temp your engine should run at. Freeway cruising, your engine temp should sit on 180 and the cooling fan should not come on.

The fan sensor turns on at 205 deg, and off at 180 deg. With the engine idling, the fan should cycle on and off as the coolant temp rises to 205 (fan on) and falls to 180 (fan off).

Putting a manual override switch in the fan circuit will give you a margin of safety in keeping the coolant closer to a constant 180 deg.

If engine temp climbs over 205 deg. and the fan stays on constantly, coolant temp will reach an equilibrium temp based on the capicity of the cooling system to dissipate heat. Obviously, the coolant temp should never exceed its boiling temp.

We use two methods of preventing boiling of the coolant. Make the cooling system more efficient at removing heat, and raising the boiling temperature of the coolant.

Bigger radiator, bigger fan, better shrouding to improve airflow through the radiator, and coolant wetter all make the cooling system more efficient.

Using a higher boiling temperature coolant (e.g. propylene glycol) and/or raising the operating pressure of the cooling system (higher psi rated radiator cap) will keep the coolant in liquid form.

Coolant expands when it gets hot, and contracts when it cools. With no airspace in the cooling system, hot coolant needs a place to go. Your garage floor is one, a coolant overflow bottle is another. For about $10 - $15, you can get a coolant recovery kit for hot coolant to reside in, and return to the radiator when cool.

Hope this was helpful.

[relaxinrob]

Jack's right. It's important to find the right mix of coolant. Plain water is the best at transfering heat, but it's boiling point is 212F not under pressure. The more pressure you put it under, the higher the boiling point, so I like to use 25% propolene Glycol and 75% distilled water. Also remember that your gauge is telling you the coolant temp, not the engine block temp. Water will give you the best heat transfer and get these two temps the closest together.....