I think I should start with

1) Removing the under drive pulleys.
2) Remove the A/C condenser that is blocking air flow to the rad
3) Install the rad seals.
4) Install electric fans
5) Go with a mix of less coolant/more water and some water wetter additive.
6) I know a proper tune can help also.

Anyone else have suggestions?

 

Your list looks good so far, and I would add to the list:

6) as far as a tune is concerned, make sure you are not running too lean either through carb settings or wrong ignition advance or both
7) Install new high flow water pump
8) Install new high flow 180* t-stat
9) make sure your front air spoiler is in place; I can't remember if 80's had a seperate spoiler or not

 

Les -
First, I'd put that vent hole back in your quarter panel...

If you have a good radiator, pump and mechanical fan, first things I'd check would be that your carb is running rich enough and that you have enough total timing dialed in - if your timing is retarded, engine temps rise dramatically. Are you using vacuum advance with that setup? A correctly set up vacuum advance will really lower temps. If you're not running vacuum advance, you need to run a lot of initial timing to keep temps down.

 

When does it run too hot? Highway, idle...???

Assuming timing, advance and carb are set up properly...the biggest improvements for my 406 came with a DeWitts radiator. Then to better manage temps at low speed idle in traffic with the AC on, I installed a heavy duty fan and clutch set-up from 76 (I think) Corvette.

When I installed a Mr Gasket high flow stat (Robert Shaw) it actually began to run too cool so I went back to a standard Stant.

 

Yeah, find out what the problem is! Forget that other crap.

There's a reason if it's overheating. That's a nice 406 you've got, but not a drag motor. The stock radiator should be able to keep it in check if it's functioning properly.

Get a 180 thermostat. Once it's warm hold your hand over the radiator and search for cold spots. If you find one, then your radiator is clogged up! So get a new one. Is it the original? You should also be running a high flow water pump and a 6 or 7 qt pan with a high volume oil pump.

Do you still have that air scoop that directs air to the rad. from below the car? Or did you ditch it with that front end?

 

ok, from your post I see your plan is to simply throw money and undiagnosed "fixes" at the problem until you find something that brings the temps down?

lets take a more logical approach:

1. you say it runs hot. What temps are you seeing that are hot? Are you only going by the gauge or have you confirmed the actual temp with an IR temp gun?
2. as Paul has already brought up, WHEN does your motor run hot? During idle and slow driving or is it during highway driving?
3. Be sure ALL the radiator/core support seals are in place and the lower airdam.
4. Is the current set-up stock with the stock fan, fanclutch. and shroud? Is the fan positioned correctly 1/2 in and 1/2 out of the shroud? Is the fanclutch operating correctly?
5. What is your timing set at and do you have a vacuum advance hooked up and connected to full manifold vacuum
6. Is your lower rad hose the correct one with the internal spring?

As torquevette mentions, forget all that other crap for now. A 406 isn't that huge of a motor and the stock cooling system should handle it fine if it's set up correctly and everything is operating as it should be.
Spending money on hi-flow water pumps, electric fans, solutions from a bottle, etc are not needed.

Removing the underdrive pulley could help but if you still have the AC system leave the condensor where it is. If you have an aluminum radiator keep your coolant mix to 50/50. A higher water % may help by a couple of degrees but the coolant has additives in it that protects the aluminum radiator from corrosion so you are best to protect an expensive aluminum rad by keeping your mix at 50/50.

The correct timing and vac adv setting is VERY important (as Lars also already mentioned) so since you already said that the car needs a tune than do that and the radiator seals and front airdam first and answer the other questions at the beginning of this reply and post back the answers.

 

B*,

6) I'll check that out (will also replace vacuum hose headlight kit from Dr. Rebuild to eliminate vacuum leaks)
7) which water pump do you recommend?
8) once again any recommendations?
9) Not sure about that one...

Hi Lars! No vacuum advance, will check timing and carb settings.

Runs hot when idling or just normal driving.

Thanks for the advice

I've read your post and made many notes!

 

why don't you have a vacuum advance on a street driven car?

 

I was told I don't need it.

 

does it have a heavy duty fan clutch? There is a lot of difference in torque between a regular and HD.

if you try and spin the fan with your finger it should only go 1/2 to 3/4 around, more than that and its too loose.

 

there are many benefits to running a vacuum advance system on a street car.
A race car doesn't need one because it would never utilize it since a race car is usually either only at idle or at WOT.
In a street car, which sees constant varying loads on the motor there are distinct advantage to running a vacuum advance system.
1. better idle quality
2. better throttle response
3. lower operating temps
4. better fuel economy

you can run without it of course, no one will say that it can't be done, but the advantages are there if you do.

If you go to my website's Tech Articles page here:
http://lbfun.com/Corvette/Tech/vettetech.html
than click on the title Header called: Timing & Vacuum Advance
read the following articles for more in depth information on the vacuum advance system:

Vacuum Advance Specs by: Lars Grimsrud
(be sure to also read the section at the bottom of the paper by Duke Williams
Timing 101 by: John Hinckley
the section on vacuum advance starts on page 3

 

according to this I should take my Unilite and toss it (no Vac advance)

Steve

 

is less advance at idle and light throttle going to make an engine run hot.

i would think not.

its the fan clutch.

 

I run a 31X19 Griffen aluminum radiator and single PermiCool electric fan, and have no problem keeping temps down.

What did Motorhead use? Isn't that his old 406?

 

yes it can. timing is a critical ingredient to what a motor's operating temp is.
Adding advance at idle and low loads (light throttle) will help with lower operating temps.
This is actually one of the key reasons why when the emissions equipment was being added onto the car in the 70's they went to ported vacuum advance rather than full manifold vacuum advance and also went to more retarded timing levels such as 2, 4, or 6º initial timing rather than levels such as 8,10,or 12º initial timing levels that most motors previously had.
With no vacuum advance at idle and lower initial timing levels it increased operating temps which was their goal to help help lower the emissions output.

I'm not saying that timing settings are definitely causing his cooling issues but timing settings CAN and in many, many threads on here it HAS been the reason or a contributing reason as it may also be a combination of more than one issue causing his problem.

At idle and/or low speed driving the fan clutch very well may be a factor, no arguement there.

Right now almost nothing is known since the OP hasn't replied back with any real info yet other than the first post which he already stated that the car needs a "tune" and another reply that he states the car doesn't have a vacuum advance system.

Since we have almost no real knowledge of his system since he hasn't let us have that info yet we don't know if his fan clutch is bad, or if he even has one. Since someone told him he didn't need a vacuum advance system, all we know someone may also have told him he didn't need a fan clutch either and he's running without one.

Point is we don't have enough real info to help him yet but I was trying to explain to him that having a operating vacuum advance system can and will help with many things, including operating temps.

 

did I say that? No, i didn't

what I did explain (or tried to anyway) was that there are many advantage to using the vacuum advance system on a street driven car.

 

Not running vacuum advance, and not getting the resultant additional 16 degrees of timing at idle and light throttle, will significantly increase engine operating temperature. Big time. If you don't have vacuum advance, make sure you're running at least 18 degrees initial timing - 22-24 would be better if the engine will take it without low rpm detonation. The more advance you can get into it the cooler it will run at light throttle.

 

Ok can one of you guys explain this? If ignition is delayed until TDC the mixture has less time to burn. I can understand that. Do more unburned vapors being exhausted cause the temp rise in the combusion chamber or is there some other mechanism at work. I would think less complete combustion would cause the chamber to run cooler so i really dont understand. I recognize that it is a well accepted premise that not enough timing causes the engine to run hotter. I would think that effect is much greater at higher loads and rpms though. Does anyone know how to explain the effect? Does anyone really understand it.

An engine at idle and light part throttle just doesn't generate that much heat as opposed to the same engine under WOT. I can't believe that even doubling the normal idle heat generation would have an impact on a cooling system that is functioning properly. Just a wild *** guess i would think an engine generates a hundred times more heat at WOT than it does at idle.

 

turtlevette

look at post #11. I already gave the link and name of the articles with additional information, including the reasons for the higher temps at retarded spark timing.
The information is in those articles, particularly the section of Lar's paper by Duke Williams and towards the bottom part of the vacuum system in John's paper

read the papers for the info, but the bottom line is that reduced spark timing increases EGT

 

My priority would be the radiator seals. The air flow to the radiator on a vette is indirect at best and bad sealing will make a huge difference for the worse. Radiator/shroud seals are easy to overlook but are more critical on a C3 corvette because or the angled radiator. Once u replace the seals u will see the difference in the condition of the seals themselves and have a better idea whether they were the problem.
And it takes a fair amount of work as the radiator and radiator shroud need to come out of the car and some of the seals are stapled onto the shroud - though i just used 3M adhesive on mine and it worked well enough. There's also a seal at the rad corners to seal radiator to the hood - buy a full seal kit.

Hope this helps,
cardo0