Correct temperature sending unit for sbc 350 to 40 series cluster (1 Viewer)

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Joined
Dec 18, 2021
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SoCal - San Berdoo
Hi all,

A tale of 2 gauges. I was thinking my 40 was overheating but I installed an aftermarket gauge and it tells me I'm actually running on the cool side. When the bosch reads 185, the OEM cluster tacks out at H. I'm guessing my sender is the wrong one for my old stock gauge cluster. Does anyone know the proper sender to get to use with my sbc 350 so my oem gauge will operate in the correct range? Links to products would be helpful.

It's a 12/70 built - 40 series with a 350 SBC conversion. I assume the gauges are original, but I can't confirm as I've only had the truck a couple of years.



20220802_185819_resized.jpg
 
If you want to run the stk gauges then you need to run the stk oil an temp senders for your 40. The oil senders threads are close enuff to thread into the SBC. The temp sender needs an adapter to screw into the SBC then the stk sender will thread into the adapter. I dont know the part #'s, but you can use the search function you'll find the #'s you need. I think I just recently purchased the adapter and temp sender from my local Toyota dealer. Maybe @ToyotaMatt or someone else will chime in with more info.
 
Hi all,

A tale of 2 gauges. I was thinking my 40 was overheating but I installed an aftermarket gauge and it tells me I'm actually running on the cool side. When the bosch reads 185, the OEM cluster tacks out at H. I'm guessing my sender is the wrong one for my old stock gauge cluster. Does anyone know the proper sender to get to use with my sbc 350 so my oem gauge will operate in the correct range? Links to products would be helpful.

It's a 12/70 built - 40 series with a 350 SBC conversion. I assume the gauges are original, but I can't confirm as I've only had the truck a couple of years.



View attachment 3076758
If you want to run the stk gauges then you need to run the stk oil an temp senders for your 40. The oil senders threads are close enuff to thread into the SBC. The temp sender needs an adapter to screw into the SBC then the stk sender will thread into the adapter. I dont know the part #'s, but you can use the search function you'll find the #'s you need. I think I just recently purchased the adapter and temp sender from my local Toyota dealer. Maybe @ToyotaMatt or someone else will chime in with more info.



i don't get into ANYTHING non-OEM factory like SBC , sorry
 
i don't get into ANYTHING non-OEM factory like SBC , sorry


He needs stk FJ40 oil and temp sending units for his 12/1970 gauge cluster .
 
He needs stk FJ40 oil and temp sending units for his 12/1970 gauge cluster .
Hi all,

A tale of 2 gauges. I was thinking my 40 was overheating but I installed an aftermarket gauge and it tells me I'm actually running on the cool side. When the bosch reads 185, the OEM cluster tacks out at H. I'm guessing my sender is the wrong one for my old stock gauge cluster. Does anyone know the proper sender to get to use with my sbc 350 so my oem gauge will operate in the correct range? Links to products would be helpful.

It's a 12/70 built - 40 series with a 350 SBC conversion. I assume the gauges are original, but I can't confirm as I've only had the truck a couple of years.



View attachment 3076758



oh sorry i misunderstood ,

YES sure i have BOTH of those IN-stock

he WILL need a TALL SENSOR UNIION TOO


i DO have my Reproduction ones available ,








1659555360360.png





1659555376161.png


1659555393484.png
 
oh sorry i misunderstood ,

YES sure i have BOTH of those IN-stock

he WILL need a TALL SENSOR UNIION TOO


i DO have my Reproduction ones available ,








View attachment 3076823




View attachment 3076824

View attachment 3076825
This is what looks to be currently installed. The sender with the union in the center of your last pic. The sender is definitely registering heat, as it starts out cold and gradually goes up and pegs H as the temp goes up. But it pegs H on my stock gauge at about 180 degrees. I thought I must have the incorrect ohm sender for the gauge or something? Can a bad sender give a false reading or will it just give no reading at all?

20220731_121551.jpg
 
If you ground the temp wire it will go to H. I suspect either a bad or most likely a wrong sensor. In Matt's last pic the adaptor I used looks like the short silver adapter on the left,fyi. My 40 is a 75 and the cluster is different. My sensor was a short one. I'm not sure if the long and short ones read the same or not. You most likely need the long one in Matts pic along w/his long union and the adaptor so it threads into the sbc. Typically the temp sensor on a sbc is in the driver side head between #1 & 3 plug. I found the pic below from another post.
AA4F796E-53D7-4A17-B241-28309B706349.jpeg
 
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@ToyotaMatt why is it necessary to use such a talk adapter. the temp sender will just sit deeper into the coolant with a short one won’t it? i’m planning on putting mine in the manifold port just beside the thermostat.
 
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From what i recall, You'll need to run the short adapter pictured on the left. It has the correct threads to screw into the sbc and accepts the Toyota sender. The sender you use is specific to your gauge cluster. I found the info using the search function yrs ago.
 
With a quick search I found Toyota's adapter # 90404-16160 or McMaster Carr #9151k96. I would suggest to confirm the #'s doing your own research. GM located the sending unit in the driver side head but in your intake works too if it fits.
 
You should put the sender in the block, drivers side I believe. t-stat is only good once it starts to warm up. EFI uses that one for the computer but on a carb application it might be ok.
 
i’ve just been told by a few race engine builders that the t stat is the most accurate measurement (not that a 40 gauge has numbers or anything) but the head will read hotter than what the whole cooling system is really at. 🤷‍♂️. who am i to argue. i dont really care where i put it. it’s not a high performance engine. i just want a gauge to tell me if my temps are climbing or are too hot on the hot summer days. both the head and the t stat are 1/2 npt threads so i need to find an adapter. i have a 3/8 npt to the correct 1972 sender (long one). i’m thinking i’ll just put a 1/2 to 3/8 npt adapter on now. it’s just not quite as long as the one in matt’s photo but i’m wondering if that’ll matter.
 
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On my sbc I had used the stock sender to the head between cylinders 1 & 3 to the instrument cluster and an aftermarket to the top of intake manifold. I found that the temp readings were very close. When I installed the Holley Sniper, it replaced the sender at top of manifold (for the EFI computer) and the digital read out on control pad was again very close to the readings for the original cluster gauge.

Your sender unit is located at top of water neck and would not be as accurate (since it reads temp after thermostat is open). In fact, since I had to use my intake location for the EFI, I decided I still wanted my aftermarket water temp gauge (in cluster under dash with an oil pressure and Volt gauge) so with no additional ports for sensor I installed an inline sleeve at upper radiator hose 3" from water neck and get similar readings as the OP is getting.

If you already have not done so, you should either bypass the ammeter and use a volt meter or modify the ammeter. Your alternator on your V8 is most likely sending more amperage (as the battery needs it) than the ammeter was designed for and could cause wire melting or worse.
 
On my sbc I had used the stock sender to the head between cylinders 1 & 3 to the instrument cluster and an aftermarket to the top of intake manifold. I found that the temp readings were very close. When I installed the Holley Sniper, it replaced the sender at top of manifold (for the EFI computer) and the digital read out on control pad was again very close to the readings for the original cluster gauge.

Your sender unit is located at top of water neck and would not be as accurate (since it reads temp after thermostat is open). In fact, since I had to use my intake location for the EFI, I decided I still wanted my aftermarket water temp gauge (in cluster under dash with an oil pressure and Volt gauge) so with no additional ports for sensor I installed an inline sleeve at upper radiator hose 3" from water neck and get similar readings as the OP is getting.

If you already have not done so, you should either bypass the ammeter and use a volt meter or modify the ammeter. Your alternator on your V8 is most likely sending more amperage (as the battery needs it) than the ammeter was designed for and could cause wire melting or worse.

i’m in process of sorting that wiring out too 🙄

i was hoping to put the temp sender in the manifold before the thermostat but i don’t think i have room. the alternatives were a sender in the thermostat housing or in the head. maybe i’ll just do the head. my worry was more about the length of adapter i need. i want to make sure i’m not going to create a problem not having the exact one seen in matt’s photo
 
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i’m in process of sorting that wiring out too 🙄

i was hoping to put the temp sender in the manifold before the thermostat but i don’t think i have room. the alternatives were a sender in the thermostat housing cabin the head. maybe i’ll just do the head. my worry was more about the length of adapter i need. i want to make sure i’m not going to create a problem not having the exact one seen in matt’s photo
Just need to replace the OEM water neck with a swivel water neck to have access to intake port (if you have one), see below. I believe that most sbc motors also have another port for temp gauge on the other head between cyl 6 & 8. Also, if you have any questions on the wiring, just ask, I spent a lot of time researching and completing the re-wire. Had way too much amperage running through harness after installing the Holley Sniper (fuel pump) and other accessories.

Water Temp Sender Locations.jpg
 
lol. changing out the neck to a swivel isn’t so easy as i’ve just learned on my chevelle. the old school alternator brackets don’t work with it and then once those are changed out belt lengths change etc! it’s a rabbit hole of its own! the head location would be way easier
 
lol. changing out the neck to a swivel isn’t so easy as i’ve just learned on my chevelle. the old school alternator brackets don’t work with it and then once those are changed out belt lengths change etc! it’s a rabbit hole of its own! the head location would be way easier
I did not realize that the stock sbc had interference for the install of the swivel water neck. I was looking at the OP photo and he does not even show the alternator installed at right side of motor. I also did not take into account that the stock intake (since the water neck is at the angle it is) may not have the threaded port that my Edelbrock does. I (with my son to teach him when in high school) built this motor off a short block so had to buy the intake manifold & carb and "aftermarket brackets" for the alternator and power steering pump. I do agree that the ports off the heads are the most accurate, but I wanted to have another temp gauge since the cluster gauge spikes to full hot when turning off motor due to the temps at the sensor plus did not know the accuracy of the sensor at head with this V8 conversion.
 
for $5 and change i got both adapters for oil and temp sender from my local gregg distributors (canadian company). now i’ll get going on the wiring again!
 
for $5 and change i got both adapters for oil and temp sender from my local gregg distributors (canadian company). now i’ll get going on the wiring again!
Not sure if there will be any helpful info in the below thread, I started a couple weeks ago related to my wiring issue. I have now fixed it with full amperage to the battery when it needs it and minimal amps drawn through the wiring harness. Deleting the ammeter was the main thing to do and since the oem wires from alt through harness to ammeter back to battery are only approximately 12ga, I wanted to stop the draw through the system. The one thing I learned after disconnecting the two wires off the ammeter and connecting together is I could of just removed one of the wires from one end of the ammeter and connected it to the other side with nut and stud saving work. Did not even have to disconnect the speedometer cable, was able to pull the cluster back enough to do the work.

 

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