A few weeks ago this thread got started about the extension and it appears they showed up on 79 L82 and not on 78's.

http://forums.corvetteforum.com/c3-g...t-spoiler.html

I really don't have any problems driving around town but the minute I get on the highway the temp climbs to over 200. Not a lot but over. Thinking it was the seal between the hood and radiator I bought them and no change. Switched to an aluminum radiator (old had a leak) and no change. Since I have an open element there was no seal between the top of the radiator and support, so put one in there and still no change. Take an exit and the temp goes down.

Could not find the extension online so I went to Lowes and purchased a black back splash. Rubber (not as sturdy as the gm extension), 4 foot by 4 inches ( gm extension is 4 3/8inches), and 8 sheet metal screws (instead of rivets).

Looked at Kaps' post #5 to get an idea what it looks like and cut mine, and attached it. There is a slit in the middle about 3/4 of the way up for the bend. Haven't decided what to do about that look. It extended the spoiler about 2 inches.

Been up on the highway 8 times since then and the car temp gauge never reached the 200 mark.

The best part if it continues to work:
cost. $2.43
If it didn't work I could just remove it very easily
If it looked ugly I could remove it

Just a FWIW:

 

I like it, any chance you cold take a ground level pic?

 

Isn't this ground level? pm me with what you need.

 

Effective and looks good too, nice

 

I was thinking , from the ground up

 

 

 

many thanks, good job

 

I was thinking fan clutch, but I guess this fixed it...which makes me curious...my 76 doesn't have that, and I can drive it ALL day long, and it won't go above 160, which is the Tstat I have in it.

What's the difference between your car and mine that yours needs that extra air diversion, and mine is fine with the normal front spoiler?


Just curious...

Glad you got your heating issue fixed.

 

I did the exact same thing and I like mine. I used s/s rivets and washers to secure.

 

Could be the timing and related to that, vacuum advance.

You should do some research on oil temperature. Yours most likely is too cold. You want the oil to get hot enough to cook out some of the contaminents that accumulate in it during cold starts and short runs where the temperature doesn't build up. Drag racers run low engine temps to keep the intake manifold and intake charge cool (more dense) for the highest performance. A regular street car doesn't need to do that and over the long run, it's not a good idea.

 

I did the same thing to my 77. Noticed it started to get hot at 70ish mph and continued to climb if I went faster.
I put the lipped part at the top instead of the bottom, it seemed able to flex better this way without me having to put a cut in the material in the middle to make the bend. I also thought the rubber was a bit flimsy and would probably bend back at high speeds reducing it effectiveness when I most needed it. So I put some sheet metal behind the rubber back splash and used 1" stainless washers and 3/16" rivits to put it all together. Looks pretty good I think. Works really well. My temps stay at 185 (thermostat temp) with a/c off up to 80 mph and about 205 with a/c on. Temps will still rise if I really get on it, but not as high as before. I'd say worth about 20 degree reduction.

 

I put a new radiator in my 75 last year when I bought it.
The old one was soft and mussy.

With a 170 degree thermostat my temp has never reached 190.

I do have a stock spoiler, but I was thinking some of you may need a simple back flush.

Ralph

 

I discovered the other day that all thermostats are not created equal.

I pulled the housing to give it a fresh repaint, and although I hadn't had any problems with the thermostat as far as I knew, decided to replace it since I had it out ('73 car).

Don't know what brand the one I pulled out was, but I went to Auto Zone to get a new one. I saw some Mr. Gasket "high flow" thermostats and bought one of them, although I figured that was just marketing hype. When I got it home and compared, I discovered that in fact the opening on the Mr. Gasket thermostat was significantly larger than the old one. You might try something like that.

 

I don't doubt that a 35 year old radiator has lost some of it's efficiency, that being said I have flushed, back-flushed and cleaned this radiator as best as I can short of having it disassembled and rodded out. The flushing did make things better and plenty of gunk came out however I wanted more cooling, and now probably have met the limit of improving the effectiveness of this radiator without shelling out some cash for a new one or an aluminum radiator (saving that for when I get the 383 installed) so for now it works as best as it can. The air dam further reduced the operating temps at higher speeds.
I figure scooping more air in can't be bad for cooling, allowing that air somewhere to escape ... that's another issue.

 

I understand that C3's are bottom feeders, meaning they do not need air coming in from the grill but need air coming from under neath.
That is why the spoilers work so well in reducing engine temperatures.

I've read that you can block off the air coming through the grill and everything will be okay.
This was done to reduce unwanted air flow at higher ground speeds.

Ralph

 

Not sure I understand what you mean. The grill air would be blocked off to reduce airflow to the radiator? Or do you mean the airdamn was used to reduce airflow under the car?

 

So did you mount the extension to the stock spoiler or to the car fiberglass itself? I have been looking at doing something similar to my 72 for a more aggressive look. I have yet to find something I like. I do like the idea of making something and customizing it yourself. Do find that the rubber back splash holds its shape adequately or is it flimsy?

 

By reducing the air to air that was going to pass under the car anyway
You end up with with less air under and sufficient air through the radiator.
Giving you greater high speed stability and a cooler engine at higher speeds.
In town driving should no be effected by these changes.

I say should not because I'm talking about healthy cooling systems.

Some poster board cut outs and a few zip ties is all it takes to give it a try.

Ralph

 

I attached it to the spoiler. At first I thought that because it is a softer material than the GM product that it would loose it's shape, make a flapping noise, etc. but that has not happened in all the miles I have put on the car. I think that because 2 inches of it is backed by the original spoiler it gives it some rigidity.

The size of your 72 spoiler might be different but the product is easy enough to buy and take a look at before attaching it with screws or rivets.