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vortec head coolant sensor '71 Chevelle

7K views 20 replies 11 participants last post by  jimfulco 
#1 ·
I'm trying to get my motor filled with fluid and started. I can hardly wait! But . . . I'm hung up on my coolant temp. sending unit right now. I replaced the 307 in my '71 Chevelle with a 1997 vortec roller block. Problem is, the coolant temperature sending unit from the '71 is too big for the hole in the vortec heads! What do I do from here?

Thanks!
 
#4 ·
You do have a perplexing problem. :D

The best solution would be, to relocate the temp sender to the intake manifold. If there is not a large enough, or any threaded pipe holes in the intake water runners, drill and tap one.

If you try to reduce the sender down in size with fittings, the sender would not be submerged in the hot coolant flow. Thus, you would get a very false reading. Reading much cooler then the actual coolant temp. Temp senders don't read steam.
 
#9 ·
or . . .

Would it be possible to just get a sensor for a '97 silverado, like where the vortec motor was originally from? Or wouldn't that match up with the factory wiring (I'm fine with splicing in a different fitting, but I do want it to actually work good).

By the way, all I'm talking about is an "idiot light" setup. I don't have a fancy temp gauge in my base malibu.

Thanks for the help so far, guys!
 
#10 ·
307malibu said:
Would it be possible to just get a sensor for a '97 silverado, like where the vortec motor was originally from? Or wouldn't that match up with the factory wiring (I'm fine with splicing in a different fitting, but I do want it to actually work good).

By the way, all I'm talking about is an "idiot light" setup. I don't have a fancy temp gauge in my base malibu.

Thanks for the help so far, guys!
Resistance values from a 1997, are way different from a 1971.

You need to use the stock sender from the 1971 application. This will work correctly with your dash 'light'/gauges.
 
#11 ·
I had the same problem when I put vortec heads on my 72 Chevy pick-up. I went to Napa and tried to find a sender that would fit the head but have the same resistance as the original. No luck, ended up putting it in the intake in the hole just under the upper radiator hose.
 
#12 ·
Routing the sensor into the intake could've been a good idea, but on the chevelle setup the thermostat housing comes out almost right on top of the 1/2" plug on my intake (edelbrock performer EPS)! There isn't room for the sensor AND the radiator hose. Other ideas? I gotta think this problem has come up with many guys, considering how popular vortec heads are!

Thanks for the help!
 
#13 ·
Can you post a picture of your intake, around the thermostat housing?

I have installed mechanical gauges in 2 intakes before. I know it can be done, even with a factory sender.

The water port runners had a 1/4" wall thickness, and with thread sealant, it will hold, and will not crack. A torque of 18-20 Foot pounds is enough.

They also make thermostat housings that "rotate", (time to improvise) but you may need to get a different upper radiator hose, to make it work without putting a 'kink' in your hose.

In a case like this, you need to be able to 'think outside of the box' to make it work.

Disregard what is the 'given', step back, look, and think 'how can I make this work'. :welcome: to Hot-roding 101. :D
 
#14 ·
307malibu said:
Routing the sensor into the intake could've been a good idea, but on the chevelle setup the thermostat housing comes out almost right on top of the 1/2" plug on my intake (edelbrock performer EPS)! There isn't room for the sensor AND the radiator hose. Other ideas? I gotta think this problem has come up with many guys, considering how popular vortec heads are!

Thanks for the help!
Your right, the problem has come up before. When you purchase an AutoMeter temp gauge, the package contains, adapters/ reducers so it will fit most applications (such as yours). If you feel usure of using a reducer based on what others have indicated, call the Autometer folks and obtain direction from them. I think you will find that its ok.
 
#15 · (Edited)
406 bug said:
Your right, the problem has come up before. When you purchase an AutoMeter temp gauge, the package contains, adapters/ reducers so it will fit most applications (such as yours). If you feel usure of using a reducer based on what others have indicated, call the Autometer folks and obtain direction from them. I think you will find that its ok.
What I have seen, the 'threaded' hole in a Vortec head is 1/4NPT.

I have "adapters" in stock, and from what I see, by the time you 'drill' them out to fit the stock "temp sender probe" they will 'break if you sneeze'.............

There is no way this will work!

rant over.

waiting for a 'pic'.
 
#16 ·
307malibu said:
Routing the sensor into the intake could've been a good idea, but on the chevelle setup the thermostat housing comes out almost right on top of the 1/2" plug on my intake (edelbrock performer EPS)! There isn't room for the sensor AND the radiator hose. Other ideas? I gotta think this problem has come up with many guys, considering how popular vortec heads are!

Thanks for the help!
On my 64 vette, the temp sensor is the same,almost right under the thermostat housing,performer rpm intake. Didn't have enough clearance. The solution was a new housing, I believe it is a billet specialties. Raised the hose about 1/2". All is fine now.
 
#19 ·
Allright, I messed around with my wife's digital camera and was unable to get a pic for you guys. Sorry. I definately cannot fit both the sensor and the thermostat housing though!

Here's what I am going to do . . . for now. Let me know what you think. What I really need to do is get this motor fired so I can get the car to my bodywork guy before winter (remember this is Wisconsin and winter is coming soon!)

I went to the parts store and got a brass plug for the sensor hole in the vortec head.

Then I got a Mr. Gasket radiator cap with a temp gauge on it!

I plan to set up full instrumentation in the future OR use one of the thermostat housings that has a sensor hole in it. I don't want to tap the manifold in another location, so I think a new housing will be best.

So. . . will the radiator cap temp gauge be okay for now? Remember I haven't run this motor yet, so I need to make sure my cooling system is working allright. What temp should I expect at the radiator cap? I've got a high flow water pump, 180 degree themostat, and I just had the radiator rebuilt and turned into a 2-row (not sure if you can believe this, but the stock 307 radiator was a single row!).

I was thinking I should be anticipating around 180-200 degrees at the cap? Any ideas? . . . or problems?

Thanks for the help, guys!
 
#21 ·
A real auto parts store might have a paper catalog with a cross-reference guide where you could see what's available with your thread size.

Might email Scoggin-Dickey's tech department (tech at sdparts.com) and see if they can help you. Surely they've dealt with this before.
 
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