Overheating a SB 68

[masonma]

I have a 1968 with a SB and a brand new Dewitt's corvette radiator.

The other day I got stuck in traffic and the cars' temp went to 210, once the car was moving again the temp would drop back down.

I would like to get some advice on what else can I do for the cooling system to solve this problem, it makes me nervous when my engine temp starts to climb and would like to not have an overheating car.

I am considering replacing the water pump with an aftermarket type such as Brassworks Flowkooler water pump or something like that. Also thought I might change the pulley sizes so the water pump and mechanical fan would spin faster.

I ordered a Dewitt radiator I asked about using an electric fan but was told that it would not be needed and instead use a mechanical fan, is this still true?

When I drive around town and have air flowing through the radiator the temp stays at 160-170, note that I am using a 160 thermostat. I have driven the car on the highway from my house down to Big Sur, Ca (150 miles round trip) and the temp stayed at 160-170 all day.

 

[516manny]

BEFORE YOU START SPENDING HUNDREDS OF DOLLARS I WOULD TRY GETTING A PRODUCT CALLED WATER WETTER MADE BY REDLINE.I RUN IT IN MY '70 454 AND HAVE HAD GREAT RESULTS.HOW IT ACTUALLY WORKS I DON'T KNOW BUT IT DOES.IT COSTS ABOUT $8 AND YOU JUST POUR IT IN WITH YOUR ANTIFREEZE.YOU SHOULD BE ABLE TO GET IT FROM ANY SPEEDSHOP.THEY CLAIM IT WILL LOWER OPERATING TEMPERATURE UPTO 20 DEG.
ALSO IF YOUR RUNNING A CLUTCH FAN YOU WOULD WANT TO CHECK THAT ALSO.WITH THE CAR COLD THE FAN SHOULD SPIN FREELY.ONCE HOT THOUGH THERE SHOULD BE NOTICABLE DRAG.
GOOD LUCK AND LET US KNOW HOW YOU MADE OUT.

 

[Hib Halverson]

First of all, 210 deg. is not overheating in the engineering sense of the word. It might be a coolant temp some of us believe is too high, but 210 in traffic then back down, is not overheating. If this were my car, as long as the coolant temp stayed around 170-180 on the highway and during hard driving, I wouldn't worry.

For comparision, I have a 71 with a modified Big-Block, electric fans and a Griffin aluminum radiator. I see 201-210 in traffic

Red Line Water Wetter will reduce coolant temperature somewhat. If you live in an area where the coldest ambient temperature allows it, reducing the percentage of antifreeze will help, too. That you mention Big Sur has me believing you are in California. If you are, unless you live in the Sierras or other cold area, you can usually run 15-20% antifreeze, distilled water and a bottle of Red Line Water Wetter. The car will cool better and the RLWW gives you the corrosion inhibiters you loose in reducing the percentage of antifreeze.

I live in Southern California and run no antifreeze at all in my Corvettes just 100% distilled water and Red Line Water Wetter.

It is unlikely a change in water pump will help in traffic.

What might help is to make sure your fan clutch assy. is the right part and is working properly. Also, verify your fan shroud is all there. For 69 and later, GM put two cooling intake holes in the bottom of the front fascia. If your 68 has not been retrofitted with them, I'd consider cutting them. Look at a 69 or later car to see what they look like and where they go.

Lastly, the OE front spoiler must be intact for the car to cool properly.