C2 Temp Question

[Rob M.]

I know this subject has been covered, but in searching the archives I couldn't find the answer to my question. So here it is, What should I expect the the temp guage to read in my 66 327/300 during normal operation?

I just replaced the radiator with a new DeWitts, put in a 180 thermostat, and new hoses, clamps etc. The temp reads 180 after warm up, but after hitting the highway for any length of time the temp reads 210 and stays there. Is that right?

I am by no means a great mechanic, so your help is appreciated.

[Joe L.]

Re: C2 Temp Question

Rob------

First of all, do you know that your temperature gauge is accurate? That's something that you need to confirm before you do anything else.

A 210 degree cruise temp seems a little bit high to me for the conditions that you described. However, there are many other factors that could influence it. Ambient temperature and the condition/configuration of your fan clutch are two. In mid-range ambient temperatures and at cruise speed, a fan clutch may have to "work" a bit. If it doesn't you could experience higher-than-normal engine temperatures. Also, the timing and advance characteristics of your engine can affect engine operating temps. There are really a lot of factors involved.

[mike cobine]

Re: C2 Temp Question

Rob,
Joe didnt' go far enough in his explaination, probably because it has been here many times.

A very common "overheating" problem is caused by reproduction sending units. Many of these do not give the same readings as the original. So the gauge says hot when it isn't.

As a result, many have taken their sending units out, placed them in water with another known good thermometer or gauge, and then watch as that water went from ambient to boiling to see how the Corvette gauge compared.

Others have purchased infrared heat thermometers and "looked" at the thermostat housing to get a real temperature.

Unfortunately, some have found they bought radiators and such needlessly as the "overheating" really wasn't.

Does yours boil over when it is running like this?

If you post where you are, you may be lucky and someone who already bought an IR thermometer may live close enough to loan it or check yours.

[Les Jacobs]

Re: C2 Temp Question

Rob Endorse the IR gun suggestion wholeheartedly as the first step to take. It could cost a 100$, but it takes all the guess work (and time) out of the process. Wish I felt this way before buying a new clutch and sender. Turns out my gauge was off by 30 degrees (really 190 not 220), and I could have breathed a lot easier sooner.

[Mike Yager]

Re: C2 Temp Question

Rob:

My '64 327/300 has never been above 200, even in traffic on the hottest, most humid day in Virginia - and it can get very hot and humid here in the summer. I would follow the suggestions in the other posts here for tracking down the problem.

[James W.]

Re: C2 Temp Question

since were on this subject, my 1964 327/300 car's temp gauge never gets to the 180 mark during any driving situation no matter what the ambient air temp is. It is usually about 2 or 3 needle width below the 180 mark. Could the problem be one of the following, faulty gauge, too much thread sealant on the threads of the thermostat, bad wiring connection at the sending unit (the clip is very loose) or a bad sending unit. To my knowledge, the sending unit is the original factory unit. The thermostat is a 180 degree unit and the radiator is the original factory installed unit and the tubes are all clean.

Best Regards,

James West
Omaha, NE.

[John H.]

Re: C2 Temp Question

Shoot the thermostat housing with an I.R. gun for the correct actual temperature and compare to the gauge reading at the same time so you can see if you have "Kentucky windage" in either direction. Temp gauges are notoriously inaccurate - I.R. guns are not; they're terrific diagnostic tools.

[Ed Jennings]

Re: C2 Temp Question

I have found that with my IR gun I can't get an accurate reading on the aluminum thermostat housing or the intake manifold. Too shiney. I have to shoot the underside of the top radiator hose or the radiator inlet neck which is black. Either place, I get a repeatable reading which is pretty consistant with the gauge.

[Rob M.]

Additional info.

Thanks. Here is some more information.

Ambient temp was not unusually hot (San Diego). The timing was just set at 6 BTDC. When I was putting in the new radiator, I looked at the fan clutch and I'm almost certain it's original (it matched the info in the judging guide) and could be the culprit. Also, just prior to the new radiator, I had a 160 thermostat and the temp gauge would clime to about 190 in similar driving situations, so I don't think it's the gauge. And when I would turn on the heater with the fan on, the temp went down. I haven't tried that with the 180.

I have not shot the thermostat housing with an IR gun and I guess that is next. But any other thoughts would be appreciated.

Thanks

[Rob M.]

Re: C2 Temp Question

Thanks to all for the suggestions. I posted a response to Joe with additional information, but it sounds like I need to find someone nice enough to shoot my system with an IR gun.

Thanks again.

[Chris R.]

Re: C2 Temp Question

If you find that the guage is inaccurate after testing can it be recalibrated or adjusted to read the correct temp?

[ronnie robertson # 36786]

Re: Sending Unit may

be causing problems. I applied sealant and teflon tape to my sending unit. I had erroneous readings which disappeared after I removed the sealant and tape. The sending unit is pipe threads and needs very little sealant. It does however need a good electrical connection to a ground.
Good Luck,

[Les Jacobs]

Re: C2 Temp Question

Chris The short answer is yes, the temp gauge can be recalibrated. Jack Humphrey is one of the gurus in this area and can best describe how to do it. (It involves revmoving the needle from the gauge, and pointing it to the correct temp). Suggest that if you need to make the adjustment that you check the archives or tag on to a thread Jack participates in.