Solution to use 1/2 npt temp sensor with vortec heads

[1972BlueC20]

Would this work??

[LockDoc]

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If the threads in the head are 3/8" NPT it should. The only problem might be that the length of the adapter would remove the temp sensor out of the coolant flow. I don't know how much of a difference that would make in the gauge reading. If you can find a fitting local I would take the temp sensor with me and make sure the end would fit into the adapter. The end of the sensor used for the stock temp gauge is pretty good sized so it may not fit into the fitting.

Some guys (including me) have had the stock sensor turned down on a lathe and re-threaded to 3/8" NPT. There are two sensors, one for idiot lights and one for gauges. The one for gauges is beefier and you can turn it down. The one for the lights can't be turned. When you turn it down do not turn it all the way up to the hex, you have to stay back 1/4" or so. That is where it is thinner and you will weaken it and it will break apart when it is tightened up. It should also be turned on a taper since NPT are tapered. That will also leave more meat toward the top. It does not have to be screwed into the head all the way. You only have to have it screwed in about half way so go easy when you thread it in too. If it leaks you can always snug it up a little more.

LockDoc

[swamp rat]

Google this ( sbc temp sensor) and look at the temp sensor images if you don't have one handy, the sensor had an extended body that protrudes into the water jacket, that protrusion would (1) have to fit inside the adapter. (2) it may not give an accurate reading if not in the water jacket, It might, I'm not certain..

[swamp rat]

Hey Doc, nice info on the turning!

[LockDoc]

Originally Posted by swamp rat

Hey Doc, nice info on the turning!

There used to be a guy on the board that was turning them down but I don't know if he is still around or not. If you know someone that works in a machine shop or has a good lathe it shouldn't be a problem.

LockDoc

[hugger6933]

Could you not just put the sensor in the intake where no adapter is needed?

[1972BlueC20]

Originally Posted by hugger6933

Could you not just put the sensor in the intake where no adapter is needed?

yes I could, that was my first thought....but I would need to buy and install a thermostat housing riser because the 1/2 NPT port is just under where the upper rad hose runs across the intake. I've also heard that some have inaccurate readings by doing this.

[1972BlueC20]

i'm still inquiring about turning down an original sensor from 1/2 NPT to 3/8, that is my preferred option and if I do, I will get 2 or 3 done at once for backups. But I am also looking for adapters or other sensors that may work.

I found this universal sensor that was on Oreillys site under my vehicle info as a "universal" part

http://www.oreillyauto.com/site/c/de...itemDetailTab_


you guys think this might work? It's 3/8 NPT so it will fit in my vortec head.

I could change the connector on the wire to work with this

[kenn]

Hello That is how I ran my sensor, and I installed a taller T-stat housing the kind with the O-ring and the angle for the hose is adjustable. I haven't started the engine yet but it looks like it will be OK.

[1972BlueC20]

Originally Posted by kenn

Hello That is how I ran my sensor, and I installed a taller T-stat housing the kind with the O-ring and the angle for the hose is adjustable. I haven't started the engine yet but it looks like it will be OK.

are you talking about using a t-stat housing that swivels?

[A1971Blazer]

If you're interested, I could turn and thread some for 3/8"-NPT.....the only issue would be having to ship them to you......if you have a part#, I could buy them here, modify and ship to you.....I'm in East Tennessee.....I have 2 CNC lathes in my shop....I cut pipe threads all the time for one of my customers.........PM me.....

[tdangle]

Is a replacement sensor that will work with the stock guage available? Or could you re-tap the head?

I'm planning on this head swap later this year and want to be prepared.

[luckysmoke]

I just put it in the manifold, works fine the airgap intake i have has a 1/2" port in the back.

[LockDoc]

Originally Posted by tdangle

Is a replacement sensor that will work with the stock guage available? Or could you re-tap the head?

I'm planning on this head swap later this year and want to be prepared.

I don't know of any direct replacement. I drilled and tapped my LS1 head for a stock '67-'72 Chevy truck sender so I see no reason it couldn't be done with a Vortec head....

LockDoc

[jocko]

Originally Posted by LockDoc

There used to be a guy on the board that was turning them down but I don't know if he is still around or not. If you know someone that works in a machine shop or has a good lathe it shouldn't be a problem.

LockDoc

It was member brian mac - he made a few for me, worked perfect. He hasn't posted since late 2014, but I'd pm him anyway - that's how I got a hold of him. Great guy to work with.

[FirstOwner69]

Here's a thread with Brian's contact info.
http://67-72chevytrucks.com/vboard/s...d.php?t=627880

Jocko is right, he hasn't posted since 2014, but his profile page shows his "last activity" was 3-12-16.

Jim

[1972BlueC20]

Originally Posted by FirstOwner69

Here's a thread with Brian's contact info.
http://67-72chevytrucks.com/vboard/s...d.php?t=627880

Jocko is right, he hasn't posted since 2014, but his profile page shows his "last activity" was 3-12-16.

Jim

Yeah I wrote him last year and never got a response. Another member a few posts above has the knowledge, experience and equipment to do it as well and offered to turn the senders down for me if needed. I may have him do it, but I just ordered a 3/8 universal sender and an original sender from Oreillys today. They will be in store tomorrow morning. If the universal unit doesn't read right then I will either get an original turned down, try and adapter, or install in the intake manifold like many others. Hopefully out of all those possibilities one will work for me.

[87Skier]

I ran into the same issue when I put a vortec engine in my Jimmy. I ended up doing some tinkering with the gauge and some resistors and use the stock vortec sending unit and stock 72 gauge with an additional resistor.

I had to give up a little accuracy on the cold side to be sure it will go to completely hot, and it reads just a little under the middle when fully warmed up.

[kenn]

Hello
Sorry about the delay I'm on and off wile at work.
Yes the t-stat that swivels. my engine is the stock 350 with alum heads.

[dmjlambert]

Originally Posted by 1972BlueC20

Yeah I wrote him last year and never got a response. Another member a few posts above has the knowledge, experience and equipment to do it as well and offered to turn the senders down for me if needed. I may have him do it, but I just ordered a 3/8 universal sender and an original sender from Oreillys today. They will be in store tomorrow morning. If the universal unit doesn't read right then I will either get an original turned down, try and adapter, or install in the intake manifold like many others. Hopefully out of all those possibilities one will work for me.

Hi, I'm interested to hear your findings on the 3/8 universal sender you got from O'Reilly's.

[74baggedbug]

I tried a lot of different sensors and none worked.. ended up gettting a local guy to machine it down for me and worked perfectly t

[davepl]

I'd tap the water pump. That way if you've messed up, you've wrecked a pump and not a cylinder head.

But I've done both the small metric Autometer sender as well as the huge 13/16" factory sender (that one into an intake manifold though), and while the tap itself can be expensive (around $50) that approach has always worked for me. It allows you to retain the right sensor and to have it in the coolant flow.

[garyd1961]

I never knew this was a real problem, I just thought I had bought the wrong sensor, lol. Anyway I put mine in the intake manifold next to the thermostat housing. It seems to work just fine.

[dmjlambert]

I prefer putting mine on the head rather than the intake manifold. I am going to have a stock sensor cut down to size and threaded. I was just wondering about 1972BlueC20's experience with that specific O'Reilly's universal sensor, just in case somebody found a sensor that just screws into a modern head without modification and works with the 67-72 temp gauge. If somebody stumbles upon a sensor that "just works" with the 67-72 temp gauge, it would be great for all of us to know. Now that I've googled for a while on that sensor, I can't find specific fitment for it but I believe it is an idiot light or fan switch.

[garyd1961]

I know the sensor should be in the head but mine couldn't work any better than it does now.
If you have vortec heads you should be running some kind of coolant bypass to keep the coolant flowing through the heads during warm up. My bypass is my heater. My heater feeds off of the same water passage that I have my sensor installed in. Coolant is constantly circulating from the heads past the sensor even before the thermostat opens. I can watch my temp gauge and it comes up just as it is suppose to. I can tell exactly when the thermostat opens by watching the gauge.
As I said I know the ideal place would be in the head but mine works just fine.