While I prefer that the temperature sending unit is at the front of the engine, it does still need to be behind the thermostat.  Installing the temperature sending unit in the upper radiator hose will have the temperature gauge reading at a much lower than actual temperature until the thermostat actually opens.  In the case of where the temperature probe or sending unit is installed in the hose and if the thermostat were to fail, the engine would be overheating long before the temperature gauge would indicate that.

Not sure why you are wanting to put the 6V temperature sending unit back in place when you could just use the ’57 and up ¼” NPT unit in the existing ¼” NPT bung.  Need more info on that.

The temperature bungs in the heads are a press fit into the heads.  Switching out the cylinder head bungs from ¼” to 3/8” or vice-versa has not been a big deal.  Once the old bung has been removed and the existing hole has been both cleaned and checked for pitting, the hole and bung are coated with Permatex #2 or other suitable sealer.  The new bung is then tapped into place.  You do want to make sure that the bung is installed with the wide portion of the threads facing the outside of the engine.

While a reducing bushing works great for using a ¼” sending unit in a 3/8” NPT threaded hole, going the other direction can be problematic in getting the larger diameter probe of the early model 3/8” sending unit to fit in the ¼” male to 3/8” female brass adapter.  As has been brought up, if actually using that 'raised' probe for a temperature reading there is going to be some inaccuracy in the gauge due to the temp probe not being directly immersed in the coolant flow.

Lorena, Texas (South of Waco)

Thanks, Ted.

Everything I've read states that you can't mix a 6v gauge with a 12v sender. If I install a 57 sender in the G head, I will also have to replace the gauge. I've already stated that the OEM gauge isn't particularly accurate, but I don't know if the reproduction gauge (probably made off-shore) is better/worse. 

It’s really more of a question of the ohms and not the voltage.  Just pick out a ¼” NPT temp sensor with approximately the same ohms and the voltage will not be a major deal if intent on using something comparable to the original sensor.

Lorena, Texas (South of Waco)

By the way, Miker, when I saw IIRC, I thought you were addressing somebody else by mistake. I later searched "IIRC." At 68 years of age, I'm very much a 20th-Century man (If I Recall Correctly). 

I went ahead and bought an adapter. What I hadn't realized is that the probe of the 55 3/8 NPT sender is the same diameter as the 1/4 NPT male end of the adapter. In other words, the 55 sender is too big. When I take the engine to Tim McMaster to be rebuilt, I will let him choose whether to tap the G head bushing for 3/8 NPT or replace the 1/4 NPT bushing with 3/8 NPT to accommodate the 55 sender. Fortunately, I was out just $6.00 for the adapter; it won't break the bank, but buying parts & tools that can't/won't be used adds up.

Well I’m 73. I should probably be using “Iirc”, since that first “I” for “if” is the important part. LOL

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

I found that Dennis Carpenter parts has the bung for the later style, I ordered one instead of continuing on my endeavour of removing the one out of my stock heads. FWIW. 

https://www.dennis-carpenter.com/trucks/cooling-system/temperature-senders/b7a-10911-a-adaptor-temp-sender-p65

I also got a rebuild kit for my truck water pump supposedly. We'll see when it comes in what I really bought.

Has anyone tried using a c-clamp to press the bung into the head? Now that the rust corrosion has been removed, maybe it will be easy to tap the replacement bung into place, but I'm thinking that pressing the bung into place might be safer.  

I had no problems tapping the bung into the head.  As I mentioned, the engine was in the car when I did it.  Don't bang on the bung, get a piece of pipe or solid bar around the diameter of the bung and tap on that.  That is what I did.  Used a very thin coat of RTV when I did it.  Just make sure it starts going in straight.

If you can get the correct angle on a press, it should be just as good.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

I'll try using a socket to tap the bung into place. Thanks.