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3/8 In Temp Sending Unit??

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LukeWarm

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Discussion starter · #1 ·
Hi Guys - I'm nearing completion of my first engine build in about 30 years, and have run in to a bit of a snag. My new Dart Iron Eagle heads have a 3/8 inch hole for the temperature sending unit, and most of them require a 1/2 inch hole. Ordinarily I'd just relocate the sending unit on the intake manifold next to the thermostat, but I have an interferance issue there with the radiator hose using the stock thermostat housing.

Any suggestions on where I can find a temp sender for a 3/8 inch hole? I'm trying to keep the engine looking as stock as possible, so I'd like to locate the sending unit in the head if possible.

Thanks as always!!
 
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#2 ·
Whatever you end up doing, make sure the sender has the same resistance figures and temperature coefficient as the one made for your gauge. There are some variations out there that aren't interchangable. A cold resistance comparison would be a good first step - should be within 10% or so of the one you have. Does that make sense?
 
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#3 ·
I was talking to Autometer about needing to calibrate a sending unit and they said as long as you use the same brand sender and gauge, that calibration is never needed. What type of gauge are you using? Have you tried to go to Home Depot, etc. and attempt to locate a reducer? They may have one that goes from 1/8" pipe to 3/8" pipe. My drivers side head uses 3/4" pipe and the passenger side uses 1/2" pipe. I don't understand that one. My intake uses 1/2" pipe as well.
 
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#7 ·
I am using a Billet Specialties 45* angled swilve type thermostat housing. It gives me plenty of clearance around my sending unit. I have my fan switch right at my thermostat housing.
 
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#8 ·
Again, what gauge?
Autometer's come with a 3/8" sender, and a fitting to adapt to 1/2"
Info for the factgory guage is above.

If you're talking the sender for the idiot light, I lived this exact same problem here a few years back. Unfortunately, I forget what the guys here told me to buy, was from some sorta mid 80's buick. Hope someone puts a number up, cause mine's gone bad and I need to buy another!
 
#9 ·
for the stock gauge, get one for an 86-ish Chev pickup.
if it's an idiot light, ask for one for an 86-ish Caprice.
if it's an aftermarket deal, then head to your local NAPA store and get some brass adapters.
 
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#10 ·
#11 ·
The sensor should be installed by itself into the water flow. If the sensor is on an adapter, the gauge will read different because its sensing bulb is out of the flow.
 
#12 ·
That depends on how long that sender is. If it reaches past the adapter then it won't make a difference.
 
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#13 ·
I would believe a trial & error test would need to be performed.

I've never had any luck with an adapter on a sensor/sending unit. Maybe its a singular case on my part.
 
Discussion starter · #14 ·
Thanks for the input everyone. My car is an RS and currently is only equipped with idiot lights. The more I think about this, it's probably about time I put some guages in this thing...especially with a $6K motor about ready to go in it this winter.
 
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#15 ·
How else would you get the sender into the head? Plus, if the adapter caused any kind of reading issue, why does Autometer send them with their temp gauges? As long as the sender comes in contact with the coolant, it will provide a reading. The coolant does not necessarily have to be flowing. All it has to do is contact the sender. I have never had a problem with my sender giving me any reading other than what the coolant actually was using an adapter.
 
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#16 ·
67CamaroRS/SS said:
How else would you get the sender into the head? Plus, if the adapter caused any kind of reading issue, why does Autometer send them with their temp gauges? ...
Click to expand...
I don't think the problem is adapting a small sender to a larger hole with a bushing which is what Autometer provides - a reducer bushing. The problem is trying to put a larger sender in a small hole. You can stack various reducers to make it work, but you'll wind up with the problem Everett is describing.
 
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#17 ·
for the idiot light, you just need a sensor for a car new enough to have the 3/8" hole, that had an idiot light.

While I'd never be without real gauges, idiot lights are good too. They holler LOOK AT ME real loud, get your attention when there is a problem, where you might not notice a gauge right away.
 
#18 ·
JimM said:
While I'd never be without real gauges, idiot lights are good too. They holler LOOK AT ME real loud, get your attention when there is a problem, where you might not notice a gauge right away.
Click to expand...

That's assuming the light bulb ain't burned out!!:yes:
 
Discussion starter · #20 ·
Well, I bought a sending unit for an 86 Caprice with a warning light. Haven't tried to install it, but it looks like it'll fit fine.
 
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davidpozzi
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