Ugh. Gauge & temp sending unit question

[4thgencreamsicle]

Alright. Working on my 69 c10. We went to replace the spade type style temp sender with the correct button style to work with my original gauge. Ran into the problem that since this is a newer engine (mid 70’s if I remember right), the temp sender is too big for the port down by the manifold. There’s a plug in another port on the top end, that looks like the right size,but I think I remember reading somewhere that it’s not a great idea to use that port (by the thermostat) because it’s more likely to overheat before actually telling you it was (?). I don’t know, is that a problem? If so, how are y’all overcoming this size issue.

The hubby and I are also discussing just getting new gauges since we also can’t seem to source any resistors for the back of the temp/fuel gauges and from what I can tell it will only get harder. My question in regards to that is if I were to get new gauges would they use the newer spade style temp sender or would we still need to sort out that aspect.
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[FirstOwner69]

I had my temperature sender turned down by member "brian mac" to fit my Vortec crate engine. Works great. I think he still provides this service. You may want to send him a PM.

[dmjlambert]

All you need to do is have the temperature sender machined down and re-threded to fit the hole in the head. I had forum member A1971Blazer turn and thread mine. Other people had it done by brian mac. Here are a couple of threads where it is discussed.
http://67-72chevytrucks.com/vboard/s...d.php?t=703388
http://67-72chevytrucks.com/vboard/s...d.php?t=627880

[pjmoreland]

I believe the fuel gauge resistor is supposed to be 100 Ohms and the temp gauge resistor is supposed to be around 85 Ohms. Resistors with at least a 5 Watt rating should work. Here are some possibilities:

TE ROX5SSJ100R

https://www.digikey.com/en/products/...J100R/10231890

TE ROX5SSJ82R

https://www.digikey.com/en/products/...SJ82R/10231888

You could use something like this to attach the resistor to the gauge.

Keystone 7312

https://www.digikey.com/en/products/...cs/7312/316685

The resistor is attached to the lugs by soldering.

[4thgencreamsicle]

Thanks for the quick responses!

Would I be risking anything by installing this new sender up by the thermostat until I can get a machined one?

We haven't had overheating issues in the past and it's always had the wrong unit in it anyway (spade style). So we've never had an actual reading on this. Wanting to know what I could expect if we used it up there in the meantime. Would it read cool until the thermostat opened up?

Cleaned up the resistors to make sure we weren't fighting corrosion and they look to be doing their thing now based on the multimeter readings. I'm still ordering resistors though and will replace those when they get here.

[Steeveedee]

If you have an intake manifold with a cooling system port that will take the sender, it should be OK there. It's ahead of the thermostat, so I wouldn't think that the difference in temperature between being in the head or in the manifold would be that great. I ran a 305 SBC in my Skylark for many years with the mechanical gauge sender in the manifold. It was an Edelbrock, not stock iron.

[pjmoreland]

I found this old thread that has an interesting discussion about using a different resistor on the back of the temperature gauge to allow it to work with a newer style small sender. The thread kind of ends without a firm conclusion though.

http://67-72chevytrucks.com/vboard/s...t=80191&page=2