Size of these holes ??? Water Temp Stuff

[mf7lakes]

I wonder if you guys could look at this picture (if I can post it) and tell what size these holes are.

I'm installing a REAL water temp gauge and probably need a thread adapter of some sort (for either one of the holes).

The new sensor is an 1/8 NPT fitting.

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Thanks in advance

 

[OLDBULL8]

3/4" NPT.

 

[ToughOldFord]

3/4" NPT.

Are you certain OB? I would have sworn they are 1/2 NPT.

 

[redneckaggie]

I would just grab a 3/4, 1/2, and 3/8 by 1/8 adapter in brass, I seem to remember that being 1/2 but I could be wrong, if you grab one of each you will be covered even if you find another location that you want to put it, Make sure that the probe sticks out from the adapter so it is in the flow of water, I tried a little test because I had a couple of people tell me it wouldnt matter to much and saw 20 deg cooler in the same location under the same conditions with probe in the flow(hotter) vs up inside the adapter

 

[redneckaggie]

i also believe that my autometer water temp came with its own adapters

 

[OLDBULL8]

Are you certain OB? I would have sworn they are 1/2 NPT.

Yeah your right, I shouldn't even be on here as screwed up as my head is with this head cold.

 

[icanfixall]

I just checked my spare block and bad head. The dash gauge sender is 3/8x18 threads pipe and the head over temp sender is 1/2x14 threads pipe...

 

[mf7lakes]

So, I gather that size is for the temp gauge sender hole.

I have seen n some threads that some guys use the temp lite sender hole for mounting their new temp sensor and then just ditch the lite.

Is that the same size hole?

And do ya'll see anything wrong with using that hole for the new sensor?

Thanks.

 

[ToughOldFord]

Yeah your right, I shouldn't even be on here as screwed up as my head is with this head cold.

Ugh, just got over that myself, I know what you mean.

 

[riotwarrior]

I'm wondering if one wants to install a temp gauge ...

Should they use the over temp hole in the pass side head? Furthest from rad furthest from cold water?

Just curious cause then you retain all the stock hardware too????



JM2CW

 

[icanfixall]

Actuallt the best place for temps is just under the thermostat but we have not place there. The flow thru the engine is from back to front. So using a head port in the back of the engine head will give a false reading. Now using the front port where the over temp sender is will show about 7 degrees higher than the combined temps from both sides of the engine. Look at the underside of the head. See that long retangle coolant passage. Thats where the coolant begins its flow under the injection pump gear housing. It then joins up with the passenger side head coolant and then it sees the stat. Look under the thermostat and you have a hole in the block. Thats the bypass when the thermostat is closed. coolant flows down thru that into the water pump at the top. Look at this pic of my open gear covers. At the top left is the bypass passage from just under the thermostat.

 

[ToughOldFord]

I use the rearward plug on the D/S head myself. I like to keep the factory equipment working:

You must be registered for see images attach

I'm wondering if one wants to install a temp gauge ...

Should they use the over temp hole in the pass side head? Furthest from rad furthest from cold water?

Just curious cause then you retain all the stock hardware too????



JM2CW

 

[LCAM-01XA]

Actuallt the best place for temps is just under the thermostat but we have not place there. The flow thru the engine is from back to front. So using a head port in the back of the engine head will give a false reading. Now using the front port where the over temp sender is will show about 7 degrees higher than the combined temps from both sides of the engine. Look at the underside of the head. See that long retangle coolant passage. Thats where the coolant begins its flow under the injection pump gear housing. It then joins up with the passenger side head coolant and then it sees the stat. Look under the thermostat and you have a hole in the block. Thats the bypass when the thermostat is closed. coolant flows down thru that into the water pump at the top. Look at this pic of my open gear covers. At the top left is the bypass passage from just under the thermostat.

I'm not so sure on the overtemp switch giving a higher reading than anyhere else. For example, you know how Oldbull always recommends placing the pyro probe in the driver side manifold between #6 and #8 cylinders - he says put it there cause these two fire right after each other so their combined exhaust will show the highest temp anywhere. So I'm wondering, can't that same logic be used for coolant as well? Since there is a port in the head above the exhaust manifold in front of the #8 cylinder, wouldn't it stand to reason that the coolant at that exact spot gets hotter than, say, the same location on the passenger side head? OK, so maybe not hotter than the engine temp gauge sensor on top of the block in the front, but maybe about the same temp? Also keep in mind that to get there the coolant first has to travel thru the water jacket surrounding all 4 cylinders on that side of the block, collecting quite a bit of heat from them in the process. As opposed to flowing past cylinder #2 only before it hits the overtemp switch at the very front of the head. So take the extended stay of "rear" coolant in the engine, add to it the extra-heating ability of cylinders #6 and #8 due to their firing order, and to me it seems likely that a sensor in that rear lower port would actually read higher than one placed in the overtemp switch location. Again, maybe not higher than the block port above the water pump that see all the coolant after its mixing and temp equalizing, but still a bit hotter than the overtemp switch.

Also from another thread, but I think it's better placed here:

Someone posted a coolant flow diagram a while back that showed the factory overtemp sensor being one of the last places that coolant flows before it gets pumped into the radiator. So it should be about the warmest place in the cooling system.

Actually that would be the engine coolant gauge sensor port, the one in the block. Looking at Oldbull's coolant flow diagram it appears that due to its location in the lower front corner of the head the overtemp switch is actually one of the first things to see coolant, as coolant only has to travel thru the #2 cylinder water jacket to reach it. Also consider the switch's engagement temperature of 239F - that's awful close to the engine's normal operating temperature of 210-220F. In comparison a small block of the same vintage runs at 200F and its overtemp switch is still set to about the same temp. And in my experience an IDI heats much faster than a gasser. Therefor it appears to me that the overtemp switch is somewhat underrated compared to what temps it would be set to if it were located elsewhere with exposure to more and hotter coolant.

Comments on that please?

 

[ToughOldFord]

I really don't think there's enough of a difference to matter one way or the other:

I really don't think the coolant temp readings anywhere in the block are going to be significant, but to be sure after the discussion we had last on this recently I ran my truck into town and back and hit each bung with the infrared gun, I got a pretty steady 192 out of the rear port and the front was floating between 191.6 to 192.3.

Then I installed an old SW mechanical gauge in the rear port. Right now I'm just setting down after running her 250 miles up and down some serious grades, from 500 ft, to several high elevations up to 3,200 feet at Buckhorn summit. Then down to sea level then back up to Oregon through the redwoods. That new engine/tranny kick butt! Anyway, I was impressed to see how accurate the factory gauge really is, cold (180ish) is on the low side of normal, 190-200 around the center, 210 is as hot as I got and the factory gauge was just right of center.

 

[LCAM-01XA]

Interesting about his gauge readings. I get 200 on the N or normal, 210-215 in the middle, and around 230 on L. Bit past L and the red light used to come on (before mech gauge sender took its place). Using IR on the rad right where upper hose goes in shows around 190 when gauge runs at 200, so gauge definitely does not read high.