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Posted By Discussion Topic: Engine Temperature -- page: 1 2     jimmott29 10-25-2012 @ 6:17 PM reply profile send p.m. Member Posts: 15 Joined: Jun 2012 Can someone tell me what the normal operating temperature is at the sensor location in the heads? Jim Mott 51f1 10-26-2012 @ 7:27 AM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 Do you mean water temperature? On a late model V-8, the thermostats open just below 160 degrees F, and the thermal switch on the driver's side of the V-8 opens between 200-212 degrees F (when the thermal switch opens, the dash gauge will go to hot). Therefore, the normal operating water temperature is between about 160 and 200-212 (206 nominal) degrees F, unless, of course, the engine is overheating, which may be considered normal by some V-8ers. The nominal thermostat opening temperature would be similar for most of the flat head engines. The 200-212 degree range is the operating tolerance for the thermal switch. If you don't have a thermal switch (straight engines), the dash gauge should still read hot at about 212 degrees. Richard This message was edited by 51f1 on 11-10-12 @ 3:46 PM Tim I 10-26-2012 @ 8:56 AM reply profile send p.m. Member Posts: 73 Joined: Apr 2010 I have nothing to add about temperature, but Holy Cow that's a beautiful car! jimmott29 10-26-2012 @ 3:41 PM reply profile send p.m. Member Posts: 15 Joined: Jun 2012 Thanks, well put. My dash temperature gauge reads almost all the way to hot when the temperature just after the thermostat is below 180 degrees. The temperatures around the radiator are much lower. This is with the high temperature switch bypased. These temmperatures are measured with a laser thermometer. Do you think the gauge in the dash is reading incorrect? Jim Mott jimmott29 10-26-2012 @ 3:41 PM reply profile send p.m. Member Posts: 15 Joined: Jun 2012 Thanks! Old Henry 10-26-2012 @ 4:36 PM reply profile send p.m. Senior Posts: 738 Joined: Apr 2010 "My dash temperature gauge reads almost all the way to hot when the temperature just after the thermostat is below 180 degrees. The temperatures around the radiator are much lower." The temperature of any surface of the engine is going to be higher than the temperature of the water inside of it when the water is circulating (not just sitting still in it) because it enters the engine much cooler than the engine and does not reach the actual engine temperature before it exits and goes into the radiator. This is illustrated as you appear to have already done. Compare the temperature of the surface of the head right where the water leaves it and enters the upper radiator hose to the temperature of the top of the radiator that is going to be pretty much exactly the temperature of the water inside of it (both because the radiator is not producing its own heat and the metal of the top of the radiator is much thinner and conducts the temperature of the water inside of it directly to the outside). You will find the actual water temperature noticeably lower than the metal of the head. In my opinion, the temperature of the water in the engine is much more critical than that actual temperature of the engine metal itself since the water is what we want to keep from boiling out and it will boil out at a much lower temperature than the engine will be damaged by any overheating. The variable temperature gauge sending unit on the right side is measuring the temperature of the water inside the head, not the temperature of the head metal itself because it is immersed in the water, not in the metal. What I did to gain some confidence in my temperature gauge is take incremental measurements of the water temperature in the top of the radiator as previously discussed and compare those measurements with the various positions of my temperature gauge needle. I discovered that my 160° thermostats didn't open to maintain that water temperature until my temperature gauge needle was at about 5/8ths on the gauge and that the water temperature at clear hot was only about 200°, still 20° below boiling my water out, so I quit worrying about it. I think if you do that same testing to see what the actual temperature of your water is at various readings on your gauge you too will be able to relax and not worry about it so much. Or, you'll know there is a real problem that needs fixing. Old Henry (The older I get, the better old looks.) This message was edited by Old Henry on 10-26-12 @ 4:40 PM Big Red 10-26-2012 @ 6:42 PM reply profile send p.m. Member Posts: 13 Joined: Aug 2011 Glad to see someone has had the same concerns as I have had. My '51 F-1 temperature stays on the dot just below the top dot on the temperature gauge, which shows it almost at the very hot reading. I have not tried the laser check, but will explore that. Thanks jimmott29 10-28-2012 @ 6:18 AM reply profile send p.m. Member Posts: 15 Joined: Jun 2012 Thanks "Old Henry" I'm an old guy myself. I really do appreciate the time that you took to provide me with a great answer. The 180 degree temperature was taken on the leaving side of the head just before the hose connects. I did notice that the temperature taken at the top of the rddiator chamber was considerabely lower. I guess in the final analysis the engine is running great. I was considering installing a new temperature (original design as the entire car is original) but I'm now believing that the results will be the same. I'm thinking that back in the day the cars had water in them & you wanted to stay well below the 200 degrees mark if possible. When I was a kid in high school, we had these cars & for some reason I don't remember the temperature gauges running hot? I'm beginning to think that the right thing to do is to install a new digital gauge so I can tell what the actual temperature is. Thanks again for the hreat input! Jim Mott 51f1 10-28-2012 @ 9:13 AM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 The temperature of the metal block is not important as long as the water temperature is normal. Those old temperature gauges are not accurate. They just let you know if the coolant is hot or cold. When the dash gauge in my '51 F-1 reads one mark above the middle mark, the water temperature coming into the radiator is actually about 160 degrees. At 160 degrees, the gauge should probably be reading in the middle of its range. Before I restored my truck, I had to put a low ohm resistor in series with the wire from the sender to get a reading in the middle of the gauge, otherwise it always read hot even though the water temperature was 160. If you want to check the temperature of the water coming into the radiator, put a candy thermometer into the water in the upper radiator tank. It should read about whatever temperature your thermostat is rated for. Another thought: If you are using a thermostat above 160 degrees, the gauge is going to read above the middle (normal) and closer to hot. Richard This message was edited by 51f1 on 10-28-12 @ 9:22 AM Old Henry 10-28-2012 @ 6:41 PM reply profile send p.m. Senior Posts: 738 Joined: Apr 2010 jimmott29: "I'm beginning to think that the right thing to do is to install a new digital gauge so I can tell what the actual temperature is." I've had that same thought. My idea is to keep everything original just as it is and install a modern mechanical gauge sender in the spare unused port on the left head and put the gauge in the glove box where I can take a peak at it if I want to without it destroying my original interior. It's an idea. May still do that some day. Old Henry (The older I get, the better old looks.) This message was edited by Old Henry on 10-28-12 @ 6:43 PM

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