I have a 73 and have an engine with aluminum heads and the original temperature gauge sending unit is larger than the new heads threaded hole in the drivers side head. I remember seeing posts about how to correct this problem with a sending unit from a later model c3 or something but cant find it also could this adjustable temp gauge resistor from willcox be useful for my problem. https://willcoxcorvette.com/corvette...resistor-68-76 I am using the factory 1973 gauge.
Thanks
Bobby

 

The factory heads use a 1/2 npt thread and most aftermarket heads use a 3/8 npt thread.You can re-machine the original part,go with the resistor,or possibly install the original unit in the intake manifold.
Hope this helps,
Dave

 

Would a 1/2 to 3/8 reducer at the plumbing supply house solve the OP
problem?
Marshal

 

No.

I had my AFR head drilled and tapped by the machine shop. I think it added $25 to the total bill of all the work they did.

 

The engine is assembled and in the car already so machine shop isnt going to work out. I actually did think about getting a 3/8 close brass nipple and a 3/8 to 1/2 female brass reducer and doing it that way to use the original sender but didnt know if that wouldn't work for some reason. would that not be a good ideafor some reason?

 

I re-machined mine to fit the cylinder head.What intake are you using?Many have an extra threaded boss you can install the factory sender in.If you try an adapter you'll have to check the clearance to your headers/ exhaust manifold.

 

Yeah, it only takes a few minutes to increase the thread size to 1/2" NPT and then you're able to use the larger sender.

 

You'll probably need the adustable resistor to dial in your gauge, but I make a sender that will screw into your 3/8 npt hole.

https://willcoxcorvette.com/corvette...79-3-8-npt-new

Willcox

 

That looks like a great solution Willcox. However, I have spent way tooooo much money with you guys the last few weeks and going to place another order in a couple days. HAHA

Assuming I have clearance with the headers is there any reason this adapter wouldn't work??

 

Thank you for the order

I don't see any reason why it won't if there is room... That will depend on how deep the npt thread is on the adapter. Has anyone else tried that part for fit, I've not.

 

You wont get an accurate reading since the sensor will sit inside of the adapter and not in the coolant flow. Close but not close enough.

 

That thought did cross my mind but i didnt know how much it would affect the reading.

 

I had the same problem with my AFR's. So I just relocated the sender in the intake as mentioned previously. Works just the same.

 

The discrepancy could be adjusted out if he gets buys and installs the adjustable temperature gauge resistor.

 

I ran into this same issue. I went with a later model water neck that has the threads in it and relocated to this position.

This will tell you when the thermostat opens and should read the temp at the tstat.




This will set you back about $8.