Coolant Temperature - What is Normal?

So I am reaching the point in the build where I am finally on the road and, having worked out an enormous amount of kinks, each drive is getting exponentially better than the last! I dare say this may even become "fun" soon at this rate! ;)

To be fair, the vast majority of issues had to do with Weber 48IDA's being improperly set up from the builder -- wrong size chokes, wrong main jets, wrong float heights, etc. Took forever to figure those things out and still a little bet left to go but all the credit for saving this motor goes to Mike Pierce, founder of Pierce Manifolds in California. There is no more knowledgeable person on the planet about Webers than Mike and he is patient, intelligent, methodical, and kind. Can't say enough good things about Mike. Mike is proprietor of Weber Carburetor Restoration, Inc. in Salinas,CA and I recommend anyone wanting to sort their Webers give Mike a call.

On today's (successful) test drive, I observed that, as with previous drives, the coolant temp never got about 70C (158F). Air temperature here was in the low 50's and car was cold soaked overnight in an unheated garage that got down to the high 30's. Driving was tame but with occasional bursts up to 5,500 rpm or so. Enough to warm the oil temp to 95C (203F). On longer stretches of gentle driving, coolant temp would settle down to 65C (149F) and oil would hang out around 85C (185F).

I have a 180 degree thermostat installed so does this mean the thermostat is never opening despite driving around for 30 minutes or so? The heater (Vintage Air Mini Gen 2) takes a long time to warm up but eventually gets hot enough that I have to turn it down. I am wondering how a 500hp motor could not heat its coolant beyond 160 degrees or so and, if thats the case, what does it mean and is it harmful? I know that cooler is better than overheating but there is such a thing as too cold, I am told. Or, should I disregard low coolant temp as potentially gauge calibration (Smiths gauges) and care more about what the oil temp is telling me?
 
I wouldn't draw any conclusions until ambient temperatures are at least 70 degrees. Depending on where coolant sensor is located it could vary from thermostat.
 
Gauge sensor is right by the distributor in the top of the water jacket. I'm wondering if I didn't stick the thermostat in backward. Can't recall paying attention to which end went in to the block...
 
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Paul T.

Supporter
Sounds like a bad, wrong sensor or possibly the gauge and sensor not matched in ohms. With that thermostat should be registering warmer than it is. Might try a point and shoot surface temp indicator at sensor location to see what it reads.
 

Terry Oxandale

Skinny Man
I run an LS engine in my project. Large radiator, with the Ford Cobra (Mustang) thermostat housing at the radiator. On moderate to warm ambient days, the sensor sees about 10-15ºF cooler values than what the thermostat is set for. On really hot days, it may get up to within 5º of the thermostat setting (190º). I know it cycles because every minute or two, I feel the heat coming off the radiator outlet in my face for a half minute, and then back to normal ambient airflow past my face. Temp gauge will vary when this happens (runs up to just under the thermostat setting (depending on the ambient temps) as the coolant gets warmer, thermostat opens, coolant cools off.
 
Thanks, Terry and all! What's the best way to test whether I've got the stat in backwards and its forced open all the time -- without having to take the housing apart? Shouldn't I be able to feel the upper radiator hose (or radiator itself) as the car is warming up and it should be cold? There is that small L-shaped bypass hose that is constantly feeding coolant through the radiator but I wouldn't think that would amount to much heat in the upper rad hose until the stat has opened.
 

Terry Oxandale

Skinny Man
The bypass will slowly warm the radiator, but once the thermostat opens, I've found the radiator rate of heating increases significantly. With only the bypass, I can feel the radiator inlet hose/tube getting warm, then that side of the radiator, then the other side of the radiator, and then the outlet hose/tube just before the thermostat opens, and then everything get hot (to the touch) real quick. I would assume there is only a single way to install the thermostat, as the larger portion of it probably wouldn't fit onto the housing cover???
 

Mike Pass

Supporter
Is the system reading correctly and accurately. Check the temperature at the sender location with an accurate instrument. Calibrate the sensor by removing and placing in boiling water with an accurate mercury thermometer and compare this to the gauge reading. I suspect that it is misreading. Once you are certain that the gauge reading is accurate then at least you are making decisions based on fact. Senders are well known for being wrong or going out of range as they rely on material which changes resistance with temperature. The resistance changes can be measured with a multimeter and compared to manufacturers data sheets. The sender may also be incorrect for the meter. Again the meter can be tested and compared to manufacturers data.
Cheers
Mike
 
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Great advice, Mike and Terry! I will do that first before tearing things apart. Won't have a chance to work on the car for a couple of weeks but will report back what I find!
 
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