[Hotrodjohn71]

Hi group. Yet another question.
By the way, I REALLY appreciate all of your consideration.
My 1967 Firebird has a 326 from 1965. The intake manifold on this motor has 2 factory holes in the water jacket casting. One is for a temp sender/switch which I use for the dummy light in my instrument cluster.
The other hole is plugged with a square head pipe plug which I am planning to remove to install the temp switch for my electric cooling fan setup.
I would like to install an aftermarket temp gauge (with the capillary tube) but I'm out of holes in the manifold so I was wondering about those adapters that let you install a heat sending unit in a heater hose.
I have an old truck which has incorporated into the heater hose a shutoff valve controlled by the heater selector levers. But my firebird has no shutoff and appears to flow water continuously through the heater core and hoses.
Any thoughts?

[steve25]

That nipple the heater hose is on at the rear of the passenger side head has a thermonic spring in it so temps might veri a great deal back there.

I would be more inclined to run a brass Tee block off of one of those front pipe holes on the water crossover your talking about at the front of the intake,

[62posbonny]

I used a fitting similar to this when I LS swapped my Cutlass. Splice into the upper radiator hose.

https://www.autometer.com/1-1-2-radi...e-adapter.html

[Hotrodjohn71]

I was not aware of the spring restrictor. I will check to see if its still intact.
If the restrictor is missing, what would the ramifications be?

[alleyCat]

I gotta be honest. I never heard of a thermonic spring nor have I seen one ! Learn something every day.

["QUICK-SILVER"]

,[/QUOTE]That nipple the heater hose is on at the rear of the passenger side head has a thermonic spring in it so temps might veri a great deal back there.,[/QUOTE]

When there and functional it does not stop coolant flow. Temperature would affect flow rate. Flow rate would not affect temperature in the hose. 180°F through a 1/4" orifice is still 180°F through a 1/2" orifice etc .etc.

[/QUOTE]I would be more inclined to run a brass Tee block off of one of those front pipe holes on the water crossover your talking about at the front of the intake,[/QUOTE]

Any block, standing up, on the crossover would be an air trap. Temp sender would have to rely on metal heat soak. That ain't good at all.

Clay

[Hotrodjohn71]

Quicksilver, I checked and the heater hose nipple is missing any kind of restrictor. What are the ramifications of this?
And do you think installing an in-heater -hose sensor would be effective?
Thank you

[Tom Vaught]

Heads ran for years without that nipple/sensor that was installed years later in the emissions vehicles. Most engines up to 1968 did not have anything more that a open nipple. Your 1965 engine and heads should have a open nipple.
Most aftermarket temp gauge (with the capillary tube) set-ups do not have super long tubes with the gages.
The water has to do a 90 degree turn in the hose to get to the inlet on the heater core. I would install a dual nipple metal part that would allow the gage sensor to be installed in the part BLOCKING part of the water flow.

This would do two things: Allow you to read the water temp before the heater core and also would be a "restrictor" device that would protect the heater core from a slug of water hitting the core and damaging it. Lots of posts about installing the 1/4th inch drilled hole restrictor before the heater core inlet. The last thing you want is your heater to start leaking after you accelerated quickly to pass a vehicle.

Tom V.

[Hotrodjohn71]

Thank you Tom. That's a darn good idea. 2 birds with one stone.

[Hotrodjohn71]

I've been researching this for hours and brainstorming this and have a couple of new questions.
All of the inline heater hose Adapters for temperature sending unit seem to only have a 1/8 npt thread for the sensor although there are adapters for 1/2, 5/8 and 3/8 hose, the temp sensor is 1/8 npt.
1/8npt is for the electric style sending unit. The smallest Mechanical (capilary tube) heat sending unit sensor thread I can find is 3/8 of an inch so it won't work with all of the adapters I've seen for heater hose as it's too big.
My
One solution to this is to run the mechanical capillary tube style water temperature Sending unit to the manifold where the stock original temperature switch sensor is, and then use that 'inline heater tube Temp sending unit adapter' made for 1/8 npt and put an electric Water temperature switch To run the dummy light on the dashboard.
My question is the stock Water temperature switch for the dummy light (in manifold stock) seems to be about 1/2 inch npt. I would need to find a switch that did the Same as that stock swhich but would fit in a 1/8 npt.

[Goatracer1]

Don't use a temp sensor for your fan that goes in the water jacket. Use either one that clamps under a intake bolt or one that has a probe that either goes in the radiator fins or in the upper rad hose. Both work well. Also you can do like I did for one of my hot rods and make an adapter that goes in the upper radiator hose. Get a piece of brass pipe (I think mine was inch and 3/4) solder a brass fitting in it the size of your temp sender. Cut your hose in half and insert. Worked great. If you put fitting on the bottom it's hardly noticeable. Paint pipe semi gloss black if color bothers you.

[64speed]

I put my snipers temp sensor in the crossover with the factory idiot light in the other opening. I put my gauge sender (mechanical) in the drivers side head

[Tom Vaught]

Originally Posted by 64speed

I put my snipers temp sensor in the crossover with the factory idiot light in the other opening. I put my gauge sender (mechanical) in the drivers side head

quote by original poster: "My 1967 Firebird has a 326 from 1965."

1965 326 Pontiac Engines did not have water temp type holes cast in the
head design. Goo info for people with later Pontiac heads with the water temp reading capability as you described.

Tom V.

[64speed]

I thought all heads had the water holes in the back?

[Tom Vaught]

All of the heads have a core plug hole in both ends of the heads (closest to the Valley Pan)
A core plug is installed on the Drivers side (rear) (Intake manifold side).
The Heater inlet hose is attached to a water nipple (1965 and later heads) on the passenger side.
The intake cross-over covers the two open core holes at the front of the engine.

Later model heads have provisions to read the head coolant temps.

My Edelbrock heads do not use the Rear Water Nipple as I run a Heater Delete Plate on my firewall.

Don't assume stuff, better to know, (and that comes with experience with the engines and how they are plumbed from the factory).

Tom V.