Temp Sender Problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Henner · 12-16-2015, 01:33 PM

Ok guys I have read and read and can not find or get a definate answer on this. I am sure by now someone has figured this out. Installed a 350 in place of a straight 6, the OE temp sender is a 1/2" and it appears i need a 3/4" temp sender for the intake or head. I can not for the life of me find a 3/4" that will let me use my factory gauge.

Thanks,

smoked68 · 12-16-2015, 01:49 PM

You may have to go get some adaptors from like Home Depo to make it work. Or... Get a mechanical gage, auto meters are nice

davepl · 12-16-2015, 02:01 PM

Brass bushing. Way easier than the other way, I paid like $50 for a tap so I could cut the threads in an iron intake to take the big fitting!

Henner · 12-16-2015, 02:53 PM

If I do a 3/4" to 1/2" bushing will the temp sender sit deep enough into the head?

**LockDoc** · 12-16-2015, 03:22 PM

Quote:

Originally Posted by Henner

Ok guys I have read and read and can not find or get a definate answer on this. I am sure by now someone has figured this out. Installed a 350 in place of a straight 6, the OE temp sender is a 1/2" and it appears i need a 3/4" temp sender for the intake or head. I can not for the life of me find a 3/4" that will let me use my factory gauge.

Thanks,

Have you actually tried the sender in the head? The head should be 1/2". I have seen intakes 3/4" but not heads....... Sounds like you have a full gauge panel but just as a heads up the senders for the idiot light gauge panels are different than the full gauge panels.

LockDoc

Henner · 12-16-2015, 03:42 PM

The heads are aluminium aftermarket heads and are definately 3/8" threads. And yes I have full gauges.
Sorry for the confusion on the above posts saying 3/4".

**dutchmanz** · 12-16-2015, 05:20 PM

Quote:

Originally Posted by Henner

The heads are aluminium aftermarket heads and are definately 3/8" threads. And yes I have full gauges.
Sorry for the confusion on the above posts saying 3/4".

I had the same issue with the Vortec heads. I bought a new brass sender for the truck and carried it to the local machine shop and had them turn it down in the lathe and then rehread it to fit the heads. There is no other sender that will give the correct resistance for the factory gauge.

**LockDoc** · 12-21-2015, 10:51 AM

Quote:

Originally Posted by Henner

The heads are aluminium aftermarket heads and are definately 3/8" threads. And yes I have full gauges.
Sorry for the confusion on the above posts saying 3/4".

Ah, that makes more sense.

I think the gauge would at least be off some if you used a reducer bushing. I'm not sure about that because I have never tried it. I tried the intake and mine didn't read even close in the intake because of the thermostat opening and closing. I have had a couple turned down for the GM crate engines I used. Make sure you have the sender for gauges and be sure they don't turn it down or thread it too far back or it will break off when you try and tighten it down. I drilled and tapped the head on my LS1 and that worked out good.

There was a member on here turning them down but I don't know if he is still around or not....

LockDoc

**FirstOwner69** · 12-21-2015, 01:02 PM

Quote:

Originally Posted by LockDoc

There was a member on here turning them down but I don't know if he is still around or not....

LockDoc

Here's a thread with good discussion and contact info for member brian mac (see post 23) who modifies senders. His last visit to the forum was Dec. 15.
http://67-72chevytrucks.com/vboard/s...d.php?t=627880

kingstrider · 12-16-2015, 05:37 PM

I used a 1/2 npt to 3/8 npt bushing when I did mine.

**dutchmanz** · 12-21-2015, 09:51 AM

Quote:

Originally Posted by kingstrider

I used a 1/2 npt to 3/8 npt bushing when I did mine.

How well does the temp gauge work with the adapter in place? I didn't go this route since the sender was not in the flow of water.

cooperhw · 12-21-2015, 12:11 PM

Quote:

Originally Posted by dutchmanz

How well does the temp gauge work with the adapter in place? I didn't go this route since the sender was not in the flow of water.

I used the adapter and mine works fine. I think it's all bathed in water whether it's "in the flow or not" so hot water will find every surface it's exposed to.

70LonghornCST · 12-21-2015, 03:00 PM

I had this same problem. My crate engine sensor opening would not accommodate the correct 67-72 sensor. I asked the same question HERE.

I was going to get an adapter, but a member chimed in who was able to machine a new OEM style to the correct size. There was also discussion about possible incorrect readings if using a brass adapter, stating that the sending unit needed to be positioned in a specific location relative to the heads, as well as the brass acting as a heatsink. Since brass is an alloy compound, its conductivity varies significantly to iron.

However, I am not too convinced about the conductivity issue, as temperature sending units are made of brass. Moreover, I was told at one point that adapters were often used on high performance applications without any issues.

My thinking is this: adapters are inexpensive. Give it a try. If the reading looks odd, or incorrect, look into getting the sensor machined to the correct size to fit your heads.

Richard

Henner · 12-21-2015, 03:13 PM

Thanks guys, I took two steps backwards this weekend while hooking up a volt meter from a 86 chevy. Appears I burn't up my circuit board. I posted over in electrical trying to get some ideas on what went wrong.

davepl · 12-21-2015, 03:19 PM

I have a spare PCB if you get desperate (I'm in WA so not nearby). They're easy enough to find but if you get stuck and can't find one, let me know!

12-16-2015, 01:33 PM	#1
Henner Registered User Join Date: Oct 2015 Location: Tuttle, Oklahoma Posts: 72	Temp Sender Problems Ok guys I have read and read and can not find or get a definate answer on this. I am sure by now someone has figured this out. Installed a 350 in place of a straight 6, the OE temp sender is a 1/2" and it appears i need a 3/4" temp sender for the intake or head. I can not for the life of me find a 3/4" that will let me use my factory gauge. Thanks,

12-16-2015, 01:49 PM	#2
smoked68 Registered User Join Date: Oct 2006 Location: Rock Hill, SC Posts: 421	Re: Temp Sender Problems You may have to go get some adaptors from like Home Depo to make it work. Or... Get a mechanical gage, auto meters are nice __________________ 1968 chevy shortbed, Dark Shadow Gray 4 bolt 383 Stroker,Weiand Super Charger, disc brakes, 9 inch, 391 gear, 20" Eagle wheels, muncie 4 speed/ Hurst shifter, 4/7 drop, Hedman midlengths, 3 inch exhaust w/ 2 chamber flows. 1966 Mustang with 306 roller, c-4, 9 inch Detroit locker rear. 1965 Fastback Mustang w/347 stroker, top loader 4spd, 9 inch detroit locker. 1966 Mustang coup, 306 roller, c4, 9 inch. 65 Cobra, 427, T6oo, 9inch, of course. First gen Hayabusa, airbox mod and running 2 exhaust cams.. Zoom Zoom Zoom

12-16-2015, 02:01 PM	#3
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Temp Sender Problems Brass bushing. Way easier than the other way, I paid like $50 for a tap so I could cut the threads in an iron intake to take the big fitting! __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible

12-16-2015, 02:53 PM	#4
Henner Registered User Join Date: Oct 2015 Location: Tuttle, Oklahoma Posts: 72	Re: Temp Sender Problems If I do a 3/4" to 1/2" bushing will the temp sender sit deep enough into the head?

12-16-2015, 03:42 PM	#6
Henner Registered User Join Date: Oct 2015 Location: Tuttle, Oklahoma Posts: 72	Re: Temp Sender Problems The heads are aluminium aftermarket heads and are definately 3/8" threads. And yes I have full gauges. Sorry for the confusion on the above posts saying 3/4".

12-16-2015, 05:37 PM	#10
kingstrider Registered User Join Date: Jan 2015 Location: Uncle Sam knows Posts: 286	Re: Temp Sender Problems I used a 1/2 npt to 3/8 npt bushing when I did mine. __________________ 1972 Cheyenne Super swb: http://67-72chevytrucks.com/vboard/s...d.php?t=684318

12-21-2015, 03:00 PM	#13
70LonghornCST Moderator Join Date: Jun 2008 Location: Modesto, CA Posts: 5,775	Re: Temp Sender Problems I had this same problem. My crate engine sensor opening would not accommodate the correct 67-72 sensor. I asked the same question HERE. I was going to get an adapter, but a member chimed in who was able to machine a new OEM style to the correct size. There was also discussion about possible incorrect readings if using a brass adapter, stating that the sending unit needed to be positioned in a specific location relative to the heads, as well as the brass acting as a heatsink. Since brass is an alloy compound, its conductivity varies significantly to iron. However, I am not too convinced about the conductivity issue, as temperature sending units are made of brass. Moreover, I was told at one point that adapters were often used on high performance applications without any issues. My thinking is this: adapters are inexpensive. Give it a try. If the reading looks odd, or incorrect, look into getting the sensor machined to the correct size to fit your heads. Richard __________________ 2018 Chevy Crew Cab 2006 Impala SS 1965 Plymouth Sport Fury 1970 Chevy Longhorn Bucket Seats Shoulder Belts Front Tow Hooks Factory Air Factory Speedwarning, Tach & Vaccum Factory Tilt CST Package AM/FM Radio Bumper Guards Richard 70 Longhorn CST Build Adding an AM/FM Decal

12-21-2015, 03:13 PM	#14
Henner Registered User Join Date: Oct 2015 Location: Tuttle, Oklahoma Posts: 72	Re: Temp Sender Problems Thanks guys, I took two steps backwards this weekend while hooking up a volt meter from a 86 chevy. Appears I burn't up my circuit board. I posted over in electrical trying to get some ideas on what went wrong.

12-21-2015, 03:19 PM	#15
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Temp Sender Problems I have a spare PCB if you get desperate (I'm in WA so not nearby). They're easy enough to find but if you get stuck and can't find one, let me know! __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible



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