Get an I.R. gun and shoot the upper radiator hose just above the thermostat housing and compare that reading against the gauge at the same time so you know what the gauge is really telling you; Google "Raytek MiniTemp" and you'll find lots of on-line sources for the MT-4 I.R. gun for around $40-$50.

I've been corresponding off-line with a C1 owner with "overheating problems" that was getting ready to throw big money at the problem, and when I finally convinced him to get an I.R. gun, he found that his coolant was at 170* when his gauge said 220*. Check it out and go from there - no point in chasing a problem that doesn't exist.

 

http://www.dewitts.com/pages/product...asp?ProdID=359

 

I have been step by step addressing high temp issues with my 66 B/B fresh rebuild,+ .060 air cond. car in Phoenix. It's been a labratory ! Originality was my priority as well as drivability of course. It is a little bit like going to the drug store and buying and trying all the cold remedys at once ; not a good idea. The IR gun is absolutely needed to establish a baseline of where your temp actually is. A couple of suggestions I used from JohnZ on this and another site: I went to a thermostat marketed by Mr. Gasket / made by Robert Shaw, more accurate better modulated flow control and I played with the "silp control" setting on my fan clutch. I have a new original appearing GM 3916141 fan clutch.( There is a Corvette Restorer article on this ) My findings were that this unit is calibrated for newer engines that are intended to warm up faster and run hotter than our mid-year stuff. If this is what you have the non fixed end of the coil spring can be rotated 180 degrees counter clock wise facing the clutch. This changes the slippage but is a noticably a little noiser and ultimately has some minimal affect on fuel milaege.These are a couple more inexpensive things to consider before major surgery.Send me a PM if you need any more info---I feel your pain. Tom R

 

I got the gun and will run a test as soon as the weather cooperates. I will report my findings when I have some.

I think my fan clutch is original (?) although I thought that the fan was only necessary at lower speeds when I don't ave a problem.

Thanks for the input. The ball is in my court.

John

 

By all means let us know how the gun works....I had a similar problem with my 327/300. Original radiator restored in 1990. It would be fine until I spent 15 to 20 minutes on the highway at 60 plus MPH. Then would inch up. Tried different things, even removing the front lisence plate, the rubber top seal from the 66's, addatives, thermostat, etc. In the end, installed a new Dewitts replacement repro radiator and problem gone. No higher than 180 now even for hours at 70 mph. But try the IR gun....let us know. Oh....Dewitts can correct code and date the radiator so its NCRS correct by the way. Mine looks pure stock.

 

Sorry about taking so long to get back on thisbut this damn computer wouldn't let me get to my thread.
I did run a test using the IR gun and although it was awhile ago, it seems that the temp was between 170 and 186 degrees depending on when i cnecked it. The ambient temperature was already lower than the summer temp so now I'll have to wait until next summer to test it again.

It does, however, look like the temp is lower than I was afraid it might be.

Now that I have the IR gun you can bet I'll keep an eye on it next year.

The bumpers have been removed for rechroming and it is just about ready for winter strorage.

Thanks for the input. It has all been helpful.