Welcome to the Corvette Forums at the Corvette Action Center!

tempeture sending unit question



i put a vortec engine in my 76 vette the hole in the vortec heads where the sending unit goes is smaller then stock heads any suggestion on what to do can i use a reducer will it word or should i try to find a sending unit that will fit

Thanks Kenny

It is totally acceptable to use a reducer. Inspect the reducer by screwing the sending unit into it and making sure the portion that goes in the water jacket does not make contact with the reducer. If it does, dremel, etc. until it is free and clear. Otherwise, it will give very false readings. None of these are 100% accurate anyway, but at least you have a better idea of engine operation.

Another suggestion, you might want to go to NAPA when they are not too terribly busy and get them to let you read through their application books. There will be pictures and descriptions of all the sending units they carry with the manufacturer, temp settings etc. You might be able to score a replacement sendor that reads the same max temp that fits your new head. Just make sure you don't get a european unit or one that has a metric thread and everything will be okay.

One finall suggestion. If you get one that fits the hole, but reads improper temps. You can go to radio shack and get resistors that you can solder in line to raise or lower the gauge readings. You would do this by putting a mechanical temp gauge in the other head and comparing the two readings. Mechanical tends to be more accurate. The guys at Radio Shack can help you choose the best one to do the trick.
Get the reducer. I have vortec heads and found a reducer at the local hardware store for $1.00. You don't want to mess with trying a different sender as the gauge is calibrated to the resistance of a particular sender. Much easier and accurate to use a reducer. I had to search the hardware store for about 30 minutes to find the correct reducer. In fact, the reducer was sitting in a shoe box full of misc. stuff they had accumulated over time. You may have to try several hardware stores to find the right one. I looked at three stores before I got lucky.


Another thing I did was cut off the end of the reducer that threads into the block. It had a very long threaded end. I wanted to get the sender as close to the hole in the block as possible, so I just used my hack saw to cut some of the thread off which placed the the tip of the sending unit inside the block.


Great point Jim.

A quick funny story. The edelbrock heads have a larger hole than the stock L98 aluminum heads for the temp sendor. I used a reducer. I also did not check to make sure the temp sending part of the reducer was not touching the sidewall of the reducer.

So, I get the car together and fire it off. Within a few moments, the temp gauge is off the chart! I go back and start checking everything. I even took the intake manifold off to make sure I did not have the gaskets backwards blocking the front ports. Of course, come to find out I was not overheating, nor did I have an air pocket trapped in that head. The sendor was just bottomed out in the reducer.

Long story short, I found the problem many hours and dollars later. So, Jim is right on. Inspect that fit very carefully.
try GM part# 8993146 sender.i work in GM parts and we have used this sending unit to correct that problem when we do engine swaps.
sending unit

so this will work with my gauge
that sender is used on guage applications, which your car has of course. you will have to change the plug end, has your old sender had a button terminal the new one has a spade terminal.no big deal.

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors


MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Advertise with the Corvette Action Center!

Double Your Chances!

Our Partners

Top Bottom