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Hello all. I have a 1976 C3 and recently rebuilt a 350 that is ready to go in. I installed AFR heads and went to put in the temp sensor and realized their thread is for 3/8 NPT instead of the stock 1/2 NPT. Does anyone know of a sensor that would fit great in there? I am finding conflicting info online or having a hard time finding a sensor that will work. Im hoping someone here has ran into this and knows what may just plug right in per say. I appreciate any help.
The aftermarket sensors don’t read right. You would have to add an adjustable resistor to temperature gauge to get it right. Wilcox Corvette was the guy for that, but he has passed and the store is gone.
Cleanest solution is to take the head to a machine shop and have the temp sensor hole drilled and tapped for 1/2” NPT then use your old sensor.
The aftermarket sensors don’t read right. You would have to add an adjustable resistor to temperature gauge to get it right. Wilcox Corvette was the guy for that, but he has passed and the store is gone.
Cleanest solution is to take the head to a machine shop and have the temp sensor hole drilled and tapped for 1/2” NPT then use your old sensor.
^^^THIS^^^
yes on each count. Tshirt
May our Lord always Bless and Keep Eddie +
Lancelot76
I tested a couple 3/8" sensors. Here is my report on the SU109. Note that I had dial it in with the Wilcox Adjustable Resistor (seems no longer available) and it tracks "adequately" from about 175° to 210° and it deviates significantly outside of that Normal Operating Range. You can read the rest of the post for other testing info.
I would suggest that you put that stock sensor in the intake manifold coolant holes--it will work adequately there..... assuming your original sensor is still functioning adequately.
Temp Sensor/Sender will work Best as GM engineers designed the system. That is installed in side of cylinder head; where it's more likely to remain submerged in coolant at all times.
JMO: Those same GM engineers must surely have understood where the exhaust ports are and where air pockets are more likely to form.
I works fine in the intake manifold if he does NOT want to get i milled for the head, nor modify the head.
I have 3 sensors on mine. 2 on intake and the 3/8" one on the head (for testing).
My stock sensors tracks wonderfully with digital indication from the EZ-EFI 2.0 which is installed on the Intake Manifold per GM on the RamJet 350.
As long as you can track the temperature appropriately you'll be fine.
The MORE important thing is to get sensor that tracks with the gauge. My original gauge slowly trended to reading low. I then got the Wilcox Adjustable Resistor and I was to dial it the original sensor to track wonderfully with the digital indication on the EZ-EFI 2.0. The important thing is to have adequate temperature readings.
If I was doing it and had the head off I'd just tap it for the big old sensor. May still need to dial it in anyway. But if worse comes to worse just install in the intake manifold hole.
Originally Posted by Rebelyell
Temp Sensor/Sender will work Best as GM engineers designed the system. That is installed in side of cylinder head; where it's more likely to remain submerged in coolant at all times.
JMO: Those same GM engineers must surely have understood where the exhaust ports are and where air pockets are more likely to form.
you say "adequate" and I say "Best". ---- I don't doubt "adequate" suits your needs ---- perhaps "adequate" is suitable for everyone's requirement ?
I do KNOW I've seen several and heard of many more, that when senders are in intake; their signals not stable because voids (air pockets) form along intake's coolant tracts.
I'm unaware of any affordable sender that senses hot air or hot steam and generates same signal consistency as when measuring hot liquid.
I ran into this same issue back in August when I got my engine back from the builder. Previously had Edelbrock heads on it where the the head was milled correctly for the factory style 1/2" thread sensor. However, as part of the engine rebuild, I upgraded to a set of AFR heads and then ran into the same issue where the sensor would no longer screw in. Unfortunately, didn't catch this until after I got the engine back. Surely wasn't going to tear the engine all back apart to have the temp sensor hole milled out. I considered moving the sensor to the top of the intake manifold, but really didn't want to butcher the new engine wire harness to extend the sensor wire up to the manifold. Luckily, have a co-worker that is pretty much a jack of all trades kinda person. He has a lathe at his home shop and was able to mill the sensor down to 3/8" so it would fit the new AFR heads. I had a spare sensor laying around anyway, so brought him two sensors...one to practice with (since he wasn't sure how it would work) and the other sensor to be the final piece. Prior to doing the work, he had me order up a 3/8"-18 NPT Hex Die that he could use on the lathe to cut the new threads with ($15.00 on Amazon). Everything worked out perfectly. Sensor screwed right in to the head with no issues. It has been on there for about 6 months now without issue. So, if you are unable to source a different sensor that will work, you might see if you can find a local machinist or someone that has a lathe that can machine yours down as well. Just a thought...
When I rebuilt my engine, I put in a new temp sensor because, well just because, why not. Replace that 45 year old sensor just because.
It would read fine between 180- 195. But.....
Above 195, 200 would read 210. 205 would read 225, etc. Holy **** I was chewing my finger nails off. I was maybe 200, but the gauge read high. And kept climbing. Nurve wracking to say the least. IR temp gun proved the issue. I installed the old sensor and all was good.
My advice. Tap out that head or machine down that stock sensor. You'll be glad you did.
Temperature Sensor
