haybabytwo

I have a 78 small block with Alum. Rad.and two electric fans, 180 deg. therm., raped headers good air dam. In the cool weather there is no problem. The problem starts when the outside temp. starts to get above 80 deg. At a idle everything is ok but when I get to 65+ mph the temp starts to climb.(210+) Slow back down and temp. drops. I looked at another C3 and under the bottom air holes,behind the air dam and in front of the radiator there was a rolled looking air ramp that directed the air to the radiator. Mine does not have this. What do you call it and where can I get one?:

cooper9811

Sounds like you need the lower front valance and/or air dam - you should be able to find that at any of the corvette parts houses (Ecklers, Keen's, etc.). If you have an AIM, it will help you determine exactly what part or parts are missing.

Keen Parts (a forum vendor listed below in "parts" section) has AIM illustrations for reference on their website - Before I bought my own copy of the AIM, I found that useful in figuring our what was missing or what to call some things.

speedreed8

Gm added a 2" extension on the L82 model lower air dam due overheating at hiway speeds.

rcread

Who raped your headers?

haybabytwo

You did! Sorry for the misspell! I'm here for help! Not your kind. Thanks!

roscobbc

On my '68 with 489 cu in I used a Dewitt ally rad - I made sure that all rubber seal and fillet pieces around the radiator surround were in place - additionally I sourced some corregated plastic sheeting (as used for signage) and filled-in some of the gaps between the radiator and shroud (using automotive body sealant to fix to shroud). This worked well - as did removing the license plate holder from its stock position. All these 'little fixes' that save a degree or two soon can add-up to a more significant temperature saving. Basically any air that comes through nose of car MUST go through radiator and shroud - its the only route the cooling air can take - make sure you use it efficiently. I do not have any problems with overheating during town driving - temp stays between 175 - 185 degrees and will rise to perhaps 190 if caught in heavy traffic for more than a half hour or so. Having said all that IF I decide to cruise at 80 mph continuously the temperature will start to climb up towards 190 degrees - dropping back to 70 mph and it stabilises at 180. I was considering one of those add-on air dams to try channel more air through the nose area, then perhaps I can keep up with all those fast running late model cars on the motorways for more than 2 or 3 minutes before having to slow down

gcusmano74

The lower air dam and all the seals around the radiator support need to be in place. You need to force the onrushing air through the radiator, and not let any go around it. That will fix most, if not all, of your problem.
Then check the fan clutch.

Gale Banks 80'

Just to ask a stupid question but have You checked the Flow direction of the Fans ? When stopped it wouldn't matter which way the Air is passing threw the Radiator but when at speed it would be a battle between the fans and the natural flow, resulting in no flow.

7T1vette

Another possibility: the lower (suction) radiator hose could be collapsing when on the road at elevated RPM and limiting water flow. With engine OFF, see how far you can squeeze that hose. There should be a steel spring inside the hose to prevent collapse. But, they rust to nothing after some years. And, some folks don't even know to install them when changing that hose (new hoses DO NOT come with the spring, unless purchased separately).

haybabytwo

Good response! Yes they are turning correct. Thanks!

haybabytwo

Does anyone know if a Indy air dam would increase the air flow?

haybabytwo

Water pump both Rad. hoses with spring on bottom are new.

kcb37

Sounds like it's all air flow to me.
I would suggest you start with the air dam piece you are missing.

lionelhutz

They actually should be off on the highway anyways since at highways speeds they will impede airflow if they have power.

BKarol

In 1979 if you ordered a L82 or got the heavy-duty radiator there was an additional extension added to the air dam. It is die cut rubber and is attached to the front of the air deflector with eight large head aluminum rivets. There were none in 78 however you could buy the piece and either put it on yourself or have the dealer install it. They no longer are available as I know. I thought Willcox was going to try but not heard.

I too had the temp go up on the highway but around town it was fine. Installed an extension like below and never over 200. You need more air for cooling. The pic was taken by forum member KAPSSA:

Robbie-T

Hi I have a 80 and in hot weather the temp goes up to 220, in any other weather it's fine. Did you end up solving this issue and what was it
thanks