Not been able to work on the car since the last post because its being held hostage by the paint shop. If the lack of air flow through the grill and under the after market 80's style bumper is my problem, would a flex fan with no clutch, so that it pulls air at any speed help with the air flow? Remember, it only runs hot while driving, not at idle. I'm not sure what chin spoiler would fit because it not an original bumper.

 

Early cars are still "bottom feeders". I have my front grills completely blocked off, and have a much larger than stock front spoiler. It dropped the rad temps by over 30* compared to when I ran it without a spoiler (not even the factory rubber lip)
Car runs at 195* all day- traffic, cruising and racing.

 

If overheating at speed, check the seals around the radiator. There needs to be no other place for the air to go than through the radiator.

Fans really don't help at speed since the speed of the car is pushing air faster than the fan is sucking.

 

Well, I'm not saying that is the problem, just something to check on, but in general, stay away from flex fans. Pure snake oil. If you choose to go back to an engine driven fan, use a clutch fan. They are what most C3 'vettes came with from the factory. They work like this: The clutch is bolted to the water pump, and the fan is bolted to the clutch. The clutch contains a viscous fluid that transfers the spin of the water pump to the fan. (Kinda sorta like a torque converter in an automatic transmission) When hot air is drawn thru the radiator,a bimetalic coil on the front of the clutch (sort of like the choke coil on the carb) senses it and tightens up the fan so it spins faster. Fan spins faster, draws more air thru the radiator, cooling it down. As the radiator cools down, the bimetalic coil senses the drop in temp, and loosens up the fan, so it freewheels, using less power from the engine. Also, the clutch never really locks up tight, and at high rpms is slipping quite a bit, using less of the engines power. Far superior to a flex fan. However, a good electric fan will sense the coolant temp and turn on when needed, and if working properly will get the job done. If your engine compartment does not show signs of extreme heat developing, it probably isn't worth changing back to an engine driven fan, but my advice to people thinking about going to an electric fan is: don't bother, you really don't get enough benefit from it for it to be worth it. Anyway, what you seem to need is for more air to be able to be pushed thru the radiator at highway speeds. When on the highway, your electric fans should never come on, airflow from the vehicle pushing thru the air should be more than enough to cool the radiator. So, like I said in a prior post, the first thing I would do in your shoes, would be to make sure that any air coming in from the front of the car has nowhere to go but thru the radiator. I mean, get picky about it. Use weatherstrip to seal the radiator against the radiator support, and seal the radiator support against the hood. Look around up front there for any little holes or cracks that air can sneak thru. Seal 'em up with duct tape or something, just to see if it makes any difference, if it fixes the problem, go back and make it pretty. One last thought: it may sound crazy, but it is actually possible that your electric radiator fans might be what is keeping air from flowing thru the radiator at highway speeds. If you live close enough to the highway, you can check it out by removing the electric fan and shroud, and taking it for a spin. Again, I am not saying that this is your problem, but I would not be the least bit surprised if your car ran nice and cool at speeds above 40 mph with absolutely no fans at all.


Scott

 

Mine runs about 180 to 190 small block, Aluminum heads aftermarket cam with A/C off over 3000 rpm I will see 200 deg. small stock chin spoiler

 

I never posted that I have an electric fan. I have a clutch fan that is probably the one that came on the car when new. It may not be working properly so I though about replacing it with a flex fan to have some positive air flow through the radiator at any speed. If the majority concensus here is that they are snake oil then I guess I will buy a new clutch for my factory fan. I will seal off the radiator when I get the car back from the painter. I really think that I need to get more air up through the bottom with a larger spoiler. Can anyone offer a suggestion for a spoiler to use that is larger than my stock '79 spoiler and that would force more air up to the radiator

 

210 is well within normal temperature range.

These cast-iron small blocks can tolerate heat up to 250 without much issue.

 

Looks like the Hayden 2799 is a favorite best buy.
http://forums.corvetteforum.com/c3-t...an-clutch.html

edit - and there is a scoop in one of the threads

 

 

I'm sorry about that, I must have confused you with a different post!!

OK, then, let's get back on track. Yeah, it sounds like that is the case, a spoiler that goes a little deeper would help. It doesn't neccesarily need to "scoop" the air up into the radiator, you just need to keep the air from going under the car. This creates a sort of low pressure area behind the radiator, which can help to suck the air thru the radiator, if you see what I mean. Remeber what I said before, "Ya gotta think like air."

If you are not having issues at low speed, that could mean that your existing clutch fan may be working just fine. It is designed to not do much at high speeds, anyway, because natural airflow thru the radiator at high speed should provide enough cooling. Here is something you could try before you go spending money on a spoiler. First, seal off the radiator. Make it so air can't sneak around the radiator. Then take a reasonably stiff piece of plastic (1/8" thick or so) and duct tape it real good to the existing spoiler. (don't stick the duct tape to any painted surface if you can help it) Start off by having it extend down an extra inch or maybe two, and take it for a spin on the highway, see if it helps. See if it hangs up on anything, like pulling into the driveway, etc. If it helps, make it look pretty, if not, don't waste your money.


Scott

 

My '79 used to run 230F on the highway.
Changed the clutch on the fan and it dropped to 210 on the highway, about 220 after a good stomp on the pedal.
With my "new" hood it runs 200-210, fast or slow on the highway.
City it drops below 200.

 

How did you change the pitch? A different fan blade? If so, where did you get it?

 

He changed the clutch.

 

Hey Imo, Which fan clutch did you use? In one of the threads in an above post they referenced a clutch for special high performance or heavy duty radiator with air. One was GM # 88961768 and should be stamped with AX to denote the heavy duty clutch but this thread was from 2006 and it ended with several suggestions but never exactly determined where to get the exact one referenced. It seems that I have a new course of action when I get the car back, starting with flushing radiator out, sealing radiator openings, fabricating scoop/spoiler and replacing fan clutch with the AX model. I will be very perplexed if my temperture doesn't come down. Oh, and I bought a bottle of water wetter. Have I left anything out

 

This may sound stupid but won't wornout soft hoses compress more at higher speeds causing less circulation and higher warmer temps?? Nobody ever mentioned hose issues. My sb use to run in the 210 to 230and I replaced the upper hose (very soft) flushed the rad and ran probably 80% water 20% antifreeze and 1/2 bottle of wetter water. Mine now runs in the 170-180 range even on a 95+ degree days in the Texas heat and I'm pleased with that. JMO!!

Good luck

 

ttxn:
upper hose doesn't "compress" during operation but the bottom can.

suspect your flush was your cure and that's exactly what the OP should do as others have suggested.

No longer are strong rad flush chems available on retail auto shelf. Do a search for oxalic acid, wood bleach.

-add-
http://forums.corvetteforum.com/c3-t...ner-flush.html

 

Well, I finally got the car back from the painter and went to work on my cooling system. I bought the heavy duty fan clutch from gm and installed it. I then sealed all of the openings around the radiator as well as the opening between the radiator support and the hood. I did a really nice job, even impressed myself. Started the engine and the fan really pulls a lot of air. I took it for a drive and to my dismay the temp runs at 10* higher than before. Now its at 220*. WHAT THE Heck !!!! Today I bought some radiator cleaner and have it in the radiator as we speak. Tonight I replaced the 2" front spoiler with a 4-1/2" spoiler. We'll see what that does when I drive it tomorrow. Keep your fingers crossed.

 

Hi Billy,

What was the temp outside when you got 220?

Tony G

 

I show 220 on my 79 but when i use my laser thermometer guage, the heads and the thermostate housing shows 180..... a lot of the indash gauges are way off.
my 2 cents

 

The outside temperture was 82 degrees and the 220 was driving between 45 and 60 mph. I didn't let it idle long enough to get an engine temperture but it never runs hot at idle. I will take it fo a drive later and see what the new spoiler does for it.