SBC cooling question

Heard a rumor that if your mechanical water temp gauge sender unit is in the lower right side of the block, that the temperature you are reading on the gauge could be as much as 20 degrees lower than if the sender is next to the thermostat housing on the intake manifold. Any truth to that? Inquiring minds want to know.........

 

I'm not sure, but it may be just the opposite. I think that the water temperature reading will be lower if the sending unit is in the intake.

Buckshot40

 

Could well do. The point is why would you want to do that? Remember you have cooled water entering from the water pump into the block. The point of the guage is to measure the temperature of the heated coolant not the cooled coolant.

Having a measure of the heated coolant is what is important that is why the sender is always somewhere at the top of the engine at or near the thermostat housing.

Putting the sender at the bottom of the block will only give you a false sense of security about engine running temperatures.

 

Yes.

For a first-gen SBC, or any engine where the coolant flow is "conventional"; i.e. it enters at the front of the block, and most of it flows to the back of the block, then up to the heads & forward again to the thermostat (with some being p***ed to the heads along the way):

The vast majority of the heat is in the upper third of the block and the heads. As a result, you can often fill the lower third to half of the water jacket with Hard Blok, or something similar, and notice virtually no change in coolant temperature. (You will see a rise in the oil temperature, which can be a good thing under certain cir***stances.)

In my limited experiments of some years back, we found well over 20 degrees difference between the bottom of the block and the top.

"Ideally" it would be best to have a temperature sender at the front of each head with a separate gauge for each, but for 99% of us, it's just fine to have a single one located in either the thermostat housing, or in a cylinder head.

The only real reason to put one in the block is for a reverse flow cooling system where the heated coolant returns from the block. Beyond that, I wouldn't put one there unless there is no other practical choice. It must be noted that OE engineers did locate the sender in the block at various times....we can only speculate that the systems had enough excess capacity that the engineers felt the inaccuracy didn't matter, and perhaps production requirements called for the sender being in the block. (shrugs)

 

Many thanks to those taking the time to provide some good answers. Many hot rods, mine included, use electric radiator fans with the thermostat switch installed in the intake manifold. Would a "T" fitting alllowing both the switch and the gauge sender be installed in the same location be a good idea?

 

That makes good sense to me.

 

I run the temp gauge in the port in the side of the head and get acceptable readings.

Running at within 1º of the 180º the thermostat opens at is acceptable to me anyway...
I have two gauges, one in in each head, and they both read virtually the same.

'40 GMC, 262" SBC, recored '48 Chevy truck radiator converted to pressure with 7 lb cap, closed coolant recovery system, 11º initial advance plus 12º vacuum advance manifold vacuum.
Will idle all day, in gear, and never change from 1º over the thermostat opening temp.

 

Error on my part........the sender is currently located in the rear port of the right head, not the block. Does this make any difference?

 

You can see the sender just below the breather cap on the valve cover.

 

It just don't matter. If, on ANY motor, the temp gauge goes up to a certain point where the thermostat opens and the temperature stabalizes, and the coolant don't puke out, the motor isn't overheating. Then, whatever the reading is, that's normal.