Hot under the hood

[eants]

OK, I'm completely out of options here. ad I can not get my car to NOT over heat while driving down the highway, However, thru city streets I'm fine. This is what I have done and the configuration thus far. Please help:



New 350, 4-bolt main ~340 HP

New "Be Cool" aluminum radiator

Twin 14 inch electric fans

New fail safe 160 degree thermostat

New water pump

All new hoses radiator and heater hoses



Running straight water with a bottle of “Water wetter”



In case it matters:



Eldebrock performer intake coupled with 650 cfm carb.

Headers

Automatic Trans which was re-built during the engine swap.



Please tell me I missed something. I’m at wits end. I’m wanting to drive to Carlisle but unless I can fix this, I’m riding with a friend in an SUV :ugh

 

[Bob Chadwick]

Have you checked to confirm that the temp that the gauge is showing is the actual temp? Shops have a gun that when pointed at the cooling system will show the temperature for comparison purposes.

What temperature do you call hot?

 

[Tweek]

Try all of the obvious stuff first, make sure the thermostat is opening up, and there is good flow in the new radiator. Did you repalce the seals around the radiator that channel the air thru it, instead of around it into the engine? Check for hoses that are collapsing, ( I have had cheep after market hoses do this) when hot and not letting the coolant flow.



Ron

 

[eants]

After being on the highway crusing at 65 for about 12 minutes, my temp gauge pegged to the right.

 

[Bob Chadwick]

After being on the highway crusing at 65 for about 12 minutes, my temp gauge pegged to the right.

Did it boil over? The cap should let go somewhere around 260 - 265 if I recall correctly.

Is your chin spoiler in place? This drives air up and over the radiator at speed and the seals that Tweek mentioned force the air over the radiator rather than allowing the air to go around it.

I suspect that Be-Cool radiator could cool the car at highway speed without a fan, assuming the air is directed properly.

Again, I would get confirmation of the actual temp.

 

[goertz]

do you have a recovery bottle? my '69 did the same thing. I'd fill it up with water, take it out for a cruise on a hot day, and after a while, temp rises. pull over and check the rad, no water. no leaks, at all. I installed a '73 style recovery tank (the '69 didn't use one at all), and voila, no more problems. I guess it was just blowing off a little bit when it was warm outside, and would run low. Now it's just fine, temp sits at 190 all the time, at idle, freeway, 100 mph, or 10. sometimes the simple things get ya. I was also at my wits end trying to figure out where the water was going. did compression tests, cooling sys pressure tests, all came out good.

 

[vmrod]

Are the valves set properly. I think if they are not properly closing, then things can get hot.

 

[JohnZ]

What's your ignition timing advance map? Is your vacuum advance functioning? After verifying the accuracy of your temp gauge with an I.R. gun (ALWAYS Step #1 with Corvette cooling issues, to see if you really have a problem or not, especially if the temp sending unit has been changed), go after a retarded timing issue and the chin spoiler. You have plenty of radiator and fan for around-town driving - heating on the highway then points to retarded timing and/or lack of airflow. 160* thermostat won't do anything - it has nothing to do with lowering operating temperature - only establishes the MINIMUM operating temperature so the heater works in the winter.

 

[lnirenberg]

I vote for either the temp sending unit or the gauge before I'd get too crazy. Unless of course steam is billowing from the hood as you cruise down the interstate, than your on your own!

 

[eants]

Prior to the engine swap, my car did not have the chin thing on it and ran fine. In fact I made the 6 hour trip to Carlisle without any issues with the original engine with over 127000 on it. Swap the engine out and use the best MY money could buy and now I can’t even enjoy it. Sorry just needed to vent.

So back to the drama. After overheating my reservoir bottle is completely empty. Once it cools of enough, the radiator is very low as well. I do not see any signs of leakage though. Could it be just running out of the overflow tube?



The timing is close. The last I checked it was about ~8 degrees BTC. Is that correct?

The valves were initially adjusted at a shop and have not been looked at since.



Thanks again to all who have replied. I’m having a hard time looking at the car in the garage these last few days.

 

[74bigblock]

You need to put the chin spoiler on it. I'll bet ya a nickle that's your problem. Remember, this is not your old motor.... it is putting out a lot more power than your stock motor, and thus has different heating trends. Around town she is not working too hard... on the highway you are getting the revs up for a lengthy amount of time without air being directed over the radiator. This will make your motor run very hot.

 

[JohnZ]

Prior to the engine swap, my car did not have the chin thing on it and ran fine. The timing is close. The last I checked it was about ~8 degrees BTC. Is that correct?

I can almost guarantee you'll overheat on the highway without the chin spoiler and a fresh engine; your car was designed as a "bottom-breather", and the spoiler is absolutely essential to deflect air up through the holes in the bumper and into the radiator.

8* sounds reasonable for initial timing, but what really matters is whether or not your vacuum advance is working; if it isn't, your timing at cruise is retarded by 15* from where it belongs, which is also guaranteed to cause highway-speed overheating.

 

[jdp6000]

I'll repeat what everyone else is saying....CHIN SPOILER. Absolute must on the highway.

Jim

 

[eants]

OK OK!!! Ordering chin spoiler today!!!!





Thanks again.

-E

 

[ruby76]

In the pic below, notice the little strips of aluminum sheet metal on either side of my center air intake duct (not hooked up). there is supposed to be large rubber/foam seals in this location. Mine didn't have it, so I fabbed these in the meantime to cure my highway overheating. Basically without them, air goes through the radiator support, then OVER the radiator. Obviously not good for cooling.