Where is the best place to aim an infrared thermometer to get an accurate reading. I have a new MidFifty gauges and it reads 3\4 all the time. The thermometer reads 180 at the thermostat housing, but anywhere else is higher. The temp creeps up in stop and go traffic. . I do not have a shroud but have one being made. Hopefully that will take care of that. Dean

 

Hi Dean!
I use the t-stat housing as a sample point too.

Your talking about the Mid-Fity reproduction style gauges that replace the original ones in the factory cluster correct? And you also got the correct sender installed that goes with that new temp gauge too ? I am sure that's a yes, but I just wanted to check.
If I recall correctly those reproduction temperature gauges are calibrated for a center reading of 160 degrees. To convert it to a 180 you simply wire a resistor in series with the gauge and sender. Mid-Fifity sells them. I have never seen them listed in their catalogs, but their part number is listed in the gauges' install instructions. Ask them for part #2688 Temp Gauge Resistor. It should reduce or recalibrate your temp gauge reading from 3/4 to 1/2 for your 180 degree water temp.

I am not sure what engine you are running or what thermostat temperature you are using. I found that using a 160 thermostat on mine keeps my temps around 170 to 175. Like yours, It does drift up some in stop and go traffic. A shroud should help you with that.

 

Hope I understood well and you want to use a hand held infrared thermometer to check your gauge readings.
There are to thinks to consider if you using a hand held infrared thermometer.
First the distance between thermometer and the spot you measure should be the same.
Second all spots you are going to measure what are not black needs a 1x1inch black tape. The color is important by infrared measuring!
Best regards
Dirk
Germany

 

hooler1, yes they are the factory style gauges with sender. I found the temp gauge instruction sheet you were talking about with the info of 160° and the resistor. Mysteriously it was not with the other instruction sheets. I have ordered the resistor. The truck has a 180° thermostat in a 1985 460. The infrared thermometer showed 200° when I finally got parked at a show last weekend. I had already ordered the shroud as it had climbed a couple times before. Hopefully that does the trick. Thanks for the quick response. Dean
Dirk, I will try the black tape . thanks Dean

 

Hey Dean,
Glad to hear you ordered the resistor. Just for my curiosity, before you install it If you could please take an ohmmeter and measure the resistance of it and tell us what it is ? I am guessing it could be around 50 ohms. But I could be wrong.

Not that you asked for any of the following, it's just some random thoughts in my head. If you feel you are running a little warm:

Check to see if you have the upper hood to valance seal installed in your hood and the lower radiator to gravel pan seals installed. Lots of trucks are missing them. But if you are running a stock style radiator I found it made about 5 to 10 degrees cooler road temps as all the air is forced through the radiator and does not by pass it. If you are looking for them check with the usual places like MidFifty, Carpenters etc. Assuming you still have or using the OE heater core. I found that made some difference in mine was having the heater hoses routed to the correct ports on the firewall and the engine. If I am recalling correctly, the lower heater core port should connect to the the intake manifold and the upper is the return to the water pump. This ensures that air is bled out as the coolant is heated up and rises thru the heater core with the valve open. Speaking of bleeding air it seems like it helps to remove the water temp sender to bleed the air out of the cooling system as you fill it. Or for less mess, some folks drill a 1/8" hole in the thermostat flange and install it so the hole is on top. Then I usually use a very large funnel to fill my radiator. Fill it so there is just a little coolant coming up its neck just to the bottom of the funnel. Start the engine and when eventually your thermostat opens, a puff of air will purge that coolant up and it will splash back down in the funnel. (Kind of fun to watch really). And I am sure you know about checking the timing to ensure it is not retarded. Some folks swear by full time manifold vacuum to your distributor. (My engine really does not like it all that much though especially when starting up hot and putting the automatic in gear). I have even had people tell me to try colder spark plugs too.
Anyway just a few things I have tried that have seemed to help me.

Indeed, a great tip from Dirk!

 

hooler1 ,thanks for the info. I will check the ohms when I get it. It may be a week or so ,going camping in the Adirondacks so not much service. I do have the hood and lower valance seals on. I made a lock plate to radiator seal from a lower valance seal as I have an after market radiator and the gap was wider. The heater core is original 56 and hoses are attached as you described. The 1\8 hole in the thermostat is a good idea. I have put about 1500 miles on since I first started driving it this summer.. The only time it creeps up is stop and go. I added water (50\50 distilled) after the first few short trips and it has stayed steady since. I don't remember what the timing was but it was about where my research said it should be. Dizzy vacuum is to Edelbrck carb recommended right side. Still working the bugs out and more work to do( they say they are never finished), but I am enjoying driving it after almost 20 years. ( working on it 9) Dean

 

Thank You Dean!
No rush on checking the ohms on the resistor.
Sounds like you pretty much have licked any heating issues with your 460. I know folks with the big block engines who really fight cooling issues.
I just have a 302 with 351 heads. It's bored .040 over (bought it that way) and it likes to run warm so I am always looking for ways to get it to run a little cooler. One idea I have been following is to modify the impeller in the water pump by cutting off 4 of the 8 blades. It is supposed to slow down the coolant flow to allow the coolant to soak up more heat before it gets flowed to the radiator. But, just like the ported vs manifold debate, there are folks who swear by it and those who say it won't work. I have an old water pump laying around that is good and I am thinking about modifying and trying it. To me changing water pumps is a lot of work though. But mine is starting to leak a little so eventually I would be changing it anyways

Have fun at the Adirondacks!

 

I solved my overheating problem by changing the electric fan to one that flows more air.

 

hooler1 , I checked the ohms on the resistor, if I did it right it read 0.10 . I but it on lowest setting .If I need to do something different let me know., I'm not much of an electritian. I haven't put it in yet ,I'm pretty sure it goes in wire from the sender. Ill let you know how much difference it makes. That water pump alteration sounds interesting I'd like to know if that makes a difference. Dean

 

Hey Thank You Dean!

I appreciate you giving it a measurement!
1/10 of an Ohm sounds extremely low but I don't know how they designed their circuit. So I would say splice it in and see if it makes a difference.
Hopefully it will re-calibrate your temp gauge to read 180 in the middle.
Next spring I am planning on changing water pumps (due to a leaky gasket behind it) and will cut off 4 blades of the impeller of another, older, but good water pump. I really want to see if this slower water flow deal is real or not. I will let you know!
Thank you again for the ohms check!

 

Well I finally got the resistor in the 56. I broke the first one installing it , between being upside down and the defrost tube there is not a lot of room. The new one MF sent me at cost and no shipping , nice of them ! The ohms were the same 0.10 . Now the gauge reads 1\4 instead of 3\4. I drove about 10 miles then let it idle for a few minutes. The infrared reads 166 on a piece of black tape on one side of the thermostat housing and 199 on the other side with no tape. Hopefully I will get the shroud in next week and we will see what difference that makes ! Well Its off to NSRA in VT for the weekend. Dean

 

Sorry to hear about the resistor difficulties and results Dean. Did the resistor they sent you have color bands on the outside of it? If so could you give the colors? Where I am going with this is if you could get another of the same value resistor and wire it in parallel or across the one you already wired into the circuit, it will half the resistance of the resistor you have already in the circuit, and should cause your meter now to read the 166 in the middle.
Enjoy your weekend!