where to place temp sensor in a 302

[40cpe]

I have bungs for a temp gauge sender on the left front, left rear, and on the thermostat housing on the manifold of my 302. The one on the thermostat housing won't read any temp until the thermostat opens. What is the best location to monitor the warmest temperature? Or do I want to monitor the warmest temp?

[Blue Futura]

I use the left front one on my 302 and my 289 . I have used the rear one too in the past.

[40cpe]

I have VDO gauges with electric senders in the '40 now and all the gauges read less than actual. I thought it might be in the ground, but I ran a jumper from the batt and still the same. The temp sender isn't installed with teflon or a sealer. The temp reads about 20 degrees less than actual so I'm going to replace it with a mechanical unit. I've read that the rear is probably the warmest part, but my laser therm shows the left front warmer.

[Y-Blockhead]

Originally Posted by 40cpe

The one on the thermostat housing won't read any temp until the thermostat opens. What is the best location to monitor the warmest temperature?

Just so I understand, your saying the bung is on the radiator side of the stat?

The reason I ask is because the return to the radiator would be the best spot I would think.

[40cpe]

Originally Posted by Y-Blockhead

Just so I understand, your saying the bung is on the radiator side of the stat?

The reason I ask is because the return to the radiator would be the best spot I would think.

Yes, the bung is between the thermostat and the radiator in the housing where the hose connects. I have a thermo switch for the electric fan there.

I would prefer to have the sensor just before the water goes through the thermostat. I considered trying to drill/tap a hole but the aluminum casting is thinner there. I am fearful that I might open a whole new can of worms with an unsuccessful tap.

[Y-Blockhead]

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Originally Posted by 40cpe

I have VDO gauges with electric senders in the '40 now and all the gauges read less than actual.

All your gauges read less than actual? Not just the water temp? And how are you measuring "actual"?

Your cast iron engine block temp will be higher than your water temperature. The coolant 'cools' the engine. If they where the same there would be no heat transfer.

Lastly, Where did FORD put the water temp sender originally?

[Blue Futura]

Originally Posted by Y-Blockhead

Where did FORD put the water temp sender originally?

Left front on the 12 or more 302s and 289s i have owned. Sometimes left front, sometimes between the carb and dist. Then there is one behind the thermostat housing on the engine side , not radiator side and it's for the heater hose . Some have a place in the left rear but not all of them. I just now went to my shop and looked at a 66 , 289 , a 79 , 302 and a 80 mustang 302 with a ford brand aluminum intake and they all had the left front , drivers side , hole for sender .

[40cpe]

Originally Posted by Y-Blockhead

All your gauges read less than actual? Not just the water temp? And how are you measuring "actual"?

Your cast iron engine block temp will be higher than your water temperature. The coolant 'cools' the engine. If they where the same there would be no heat transfer.

Lastly, Where did FORD put the water temp sender originally?

The probe of the temp sensor should be in the water flow and doesn't measure block/manifold material temp. The block/manifold provides the ground return to the gauge. I'm measuring temp by laser thermometer and by digital thermometer with probe in rad water. They both agree with the thermostat rating. Temp gauge shows about 20 degrees cooler.

I have a mechanical oil gauge T'd in with the VDO sensor under the hood. Oil pressure reads about 10# less on the VDO.

Comparing voltage at the battery with the VDO gage, the dash gauge reads about 1V lower.

Fuel gauges are relative anyhow, I compensated with the float adjustment.

It would be easy to argue that there is a wiring problem somewhere. Maybe so, but I've done all I can without tearing it all out and starting over. This water temp thing is the one that really bugs me. I have a new radiator with an electric fan controlled by a thermo switch and I would like to monitor it for a while.

[Y-Blockhead]

Originally Posted by 40cpe

The probe of the temp sensor should be in the water flow and doesn't measure block/manifold material temp.

NO SHIT?? I just wanted to determine if your "actual" was taking with a IF Harbor Freight like probe measuring the outside of the manifold. Guess I got my answer...

Originally Posted by 40cpe

It would be easy to argue that there is a wiring problem somewhere.

Guess you got your answer too. Either that or VDO gauges are NFG.