Engine Operating Temps

[Steve Cassani]

I have an SPF with a 351 Windsor stock block. The cooler temperatures in Montana have left me with a concern for the engines operating temperatures:

Ambient air Temp (F) Water Temp (C) Oil Temp (C)
85-90' 69-74' 66-68'
70-85' 64-68' 64-66'
50-70' 64-68' 55-62'

With ambient temps in the 70-85' range, a check of the hoses leading to and from the radiator indicates that the main hose leading to the top of the radiator is cool. The burden for circulating water through the cooling system is being carried by the half-inch bypass hose. At 85-90', the main hoses are warmer but still somewhat less than one would expect if the thermostat were fully open.

My diagnosis is that the radiator is cooling more efficiently than the engine is generating heat. This explains why the thermostat is not fully open even on the warmest days. In cooler weather, the thermostat is closed and the volume and rate of circulation provided by the by-pass hose is enough to maintain temperatures at the indicated levels. If I'm right, replacing the 160' (F) thermostat with a 180' (F) unit will not help to increase operating temperatures. The by-pass will continue to maintain flows at a minimal level and this rate cools the engine to the indicated temperatures.

Discussion with Dynamic rules out covering a portion of the radiator.

When caught in traffic, the water temps rise fairly quickly and the fans come on at an indicated 93' (C). The fans are adequate to maintain water temps at this level until I am traveling at a sustained 35-40mph. Then the water temps drop fairly quickly to the indicated range.

The oil cooler is not connected. As you see from the table, oil temps track with the indicated water temps. I'm using Mobil One 15-50.

I haven't experianced any problems with engine performance or drivability. I've been through three oil changes and the oil looks great. As you might expect, the car has to be on the road for 15-20 minutes, at 2,100 RPM, before the oil temp guage comes off the peg. Water temps are achieved in less than 3 minutes.

[SCOBRAC]

When did they start using the metric system in Montana?? What's it all mean in American?

[MidOHasp]

Steve,

I am experiencing similar results in Ohio, so it's not a Montana thing.

Just kidding . . . the SPF radiators are just THAT good. Seriously. Those temps are about identical to what I see. If it's not well over 70 (F) degrees ambient, I can't get the water temp to go over 70 (C) degrees.

I run a Robertshaw hi-performance thermostat with the really nice 3 machined bleed holes. My "by-pass" is blocked off! I'm maintaining those temperatures by flowing whatever water is going through those 3 tiny holes and just ambient air cooling the engine.

I have a 180* stat.

If you want it to run warmer, I suggest buying a replica with a lesser radiator.

[djseed]

I just changed my thermostat in my SPF from 160 to 180 to put more heat in the engine. On the highway the BB runs at 180. In town it goes to 200. I think the shroudding on the rad is excellent and that is why it cools so efficiently. I do have the oil cooler hooked up but it has a Canton 215 thermostat on it. I believe it has only opened a few times. I considered the 195 thermostat but the fan is designed to come on at about 195, so I did not want to run the fan all the time. The only other change I made was to change the alternator to a 140 watt unit because the underdrive pulley set on the motorvdid not allow the 77 watt stock unit to spin up sufficiently to yield enough power.

[Steve Cassani]

Thanks, guys. I'm not going to worry over this issue any more.

The engine shows no undue signs of loading up with carbon, plugs look good and the oil is in excellent condition, changing every 3,000 miles. Winter is coming and daytime temperatures are in the mid to low forties. I can't change that so the roadster is in storage until May.

[Nuke427]

Radiator being too good doesn't have a whole lot to do with cool temperatures during cool weather. If your thermostat is fully closed, it doesn't matter how good your radiator is. As stated earlier, it depends on how much bypass flow you have. My car used to run cold in the winter also. I have a CSI thermostat that had too much bypass around the thermostat. I changed it and now I'm happy with an 88 C engine, Summer and Fall. If your engine temp is changing with the weather, you need to re evaluate your thermostat/housing setup. A cool engine will not perform as good as a warmer engine. Contrary to opinion. A hot engine with cold intake air is the best formula.

[BMK]

Nuke 427

After a night drive in South Australia's 10c (50f) it dropped even lower and I'm positive the engine began to sing as it got colder.



I was freezing but hell I was flying..

Bernie

[Nuke427]

By the way, 64 C is only 147 F. I think that's a little cold for a Ford V-8. 68 C is only 154 F, still too freakin' cold.

For you non metric types F = C X 9/5 + 32

[Carroll DeWeese]

My SPF has an oil cooler and I get similiar results. On the highway, even in warm weather, I run oil a little over 70 c and water less than 80 c unless I diliberately keep my gearing with the RPMs near 4000 or above. This winter I am going to install a temp controlled oil by-pass of the oil cooler to get higher temps on steady lower RPM situations (e.g., highway driving). Oil coolers are not needed except under race-type driving situations.

[BPWilliams]

Remember a cold enging generates more HP, but how is your oil pressure? Mobil 15-50 gets pretty thick at those temps. I have a BB 429SCJ that runs a 180 thermostat and I need to block off my oil cooler duct because the oil gets too cold, even in AZ. I also run Mobil 15-50 for track events and on the street I see a 5 to 15 psi increase in oil pressure at cruzing speeds because of oil temp. You might want to change oil to a more friendly version for cold weather unless you plan on tearing up the track on the weekends.....

Keep it above 100.........

Brian

[Steve Cassani]

Oil pressure is commonly between 72 and 85 pounds. It will drop to 55 during idle after running steadily above 2,800 RPM.

[Nuke427]

Originally posted by BPWilliams


Remember a cold enging generates more HP, but how is your oil pressure? Mobil 15-50 gets pretty thick at those temps. I have a BB 429SCJ that runs a 180 thermostat and I need to block off my oil cooler duct because the oil gets too cold, even in AZ. I also run Mobil 15-50 for track events and on the street I see a 5 to 15 psi increase in oil pressure at cruzing speeds because of oil temp. You might want to change oil to a more friendly version for cold weather unless you plan on tearing up the track on the weekends.....

Keep it above 100.........

Brian

Have you ever heard of "I need to warm it up before I get on it?" Running cold temperatures may increase your HP but keeping the engine temp in the 150 degree range is just wrong. Along with oil temperature in that range. It's best lubricating properties are in a higher temp than that. You want your car up to operating temps atleast ~170 and oil to be at a similiar temp. Like I stated earlier, HOT combustion, cold intake = most HP.

[Steve Cassani]

I don't disagree that higher operating temperatures would be better. I haven't been able to figure out how to increase the water and oil temps from the values shown in my initial post.

Replace 160' thermostat with 180': Not likley to help, since the bypass is limiting the flow to the current level.

Close by-pass and replace thermostat with 180' unit with minimal by-pass: MidOhasp has installed a thermostat that features a restictive by-pass, and he is experiencing temperatures the same as mine under similar air temps.

Restrict the flow of air to the radiator: Dynamic reports this will jeopardize the internal mechanics of the radiator, especially the design features that govern the automatic fans.

Switch from Mobil One 15-50 to a lighter weight oil. Maybe 10-40?

Don't get me wrong; I appreciate the dialog and you folks are helping. Maybe I have to accept that a 351 stock block, installed in a car capable of supporting a much larger engine, will run cooler than folks expect of a performance tuned engine.

The engine runs fine. The heater isn't much help....

[Nuke427]

Steve, don't misunderstand me either. My main objective was to explain my point of view on a "cold" engine. It's well known a cold motor puts out more power but that's due to a cold motor can't heat up the intake air so it's freakin' cold and a lot more dense so there's a ton of O2 in it to burn. You want your block to be nice and warm. I know the "problem" people always talk about with old V-8's is the overheating. But if you don't get your car up to normal operating temperature which I consider to be 170+, I wouldn't be abusing it. Why do you think they make thermostats? To heat the motor up, not to cool it down. If it was for cooling, there wouldn't be one.

[Michael C Henry]

The bypass is only supposed to circulate from just under the thermostat to the coolant pump and back through the block again. Coolant is flowing , but just in that circuit. When coolant reaches the opening temp the thermostat, it opensand coolant flows through the radiator .Untill the thermostat opens there should be no flow through the radiator. They do makebad thermostats and they do go bad.If you close off the bypass coolant will be uneven stscking at the top of the cylinder heads. The thermostat will open violently. causing a sudden surge and so forth.

[BPWilliams]

EASY Nuke!

Some things in life I take for granted, like your engine needs to be at operating temp prior to getting on the track. (that is why they have warm up laps) and yes a 160 thermostat is OK, as long as your oil temp is above 200. The problem is that the oil will not function properly at cold temps. It just can not burn off the containments that get picked up along the way. I in no way endorse getting on a cold engine, or cold tires for that matter. Warming up your gear is a given (I think) for most of us out there that use our cars on the track. I think that if you look into your specifications your oil pressure is way to high for that motor at those temps, that was my point.......

L8R,
Brian

[Steve Cassani]

I've resurrected this old (ancient?) thread to explain how the problem of chronic cold operating temps - water and oil - was solved.

I worked with a mechanic in Manhattan to (1) insert a sleeve in the by-pass, restricting the flow around the thermostat and (2) install a 180' themostat. With the reduced rate of flow through the by-pass the cooling system is no longer adequate to maintain water temperatures much below 78'C, even with air temperatures below 50'F. When air temp rises to 74'F or more, water temperature rises to 88-90'C, causing the thermostat to open. Once open, water temps hold 83'C when air temperature exceeds 100'F.

Oil temperature is consistently 74-76'C when water temperature measures 83'C. If air temperature drops below 74'F, water temperature hovers around 76-78'C and oil temperature ranges from 64-68'C.

There are no problems driving in traffic and the fans come on only after the car has been run hard and parked, and then only for a minute or so. Water temperature never exceds 93'C when the fans begin.

Barring better advice from this group, I belive the problem has been solved.