You have the basic idea, but backwards. The cap allows higher than ambient pressure which RAISES the boiling point of the coolant.

A point that many folks don't realize is that water is the best coolant, better than a water/anti-freeze combination. If you decide to run straight water, you should add an anit-corrosive and water pump lubricant. As long as freezing is not a concern that is the most efficient coolant.


Pete

 

Actually attempted to perform the above test and at 1500 RPM the test showed the radiator was cooling by 25 degrees or so. In retrospect, the problem is that there is no load so the engine is not creating more heat - I assume that the radiator is able to cool as long as the top temp is not too high. I'm guessing the radiator is not able to pass enough coolant to offset higher temps.

Of course, I'm totally unsure of where this all is at this juncture. Really don't want to put the radiator back in without some reasonable belief that the problem is solved - may have to do that.

Anyone know what combination of water/coolant is good for anti-corrosion and water pump lubrication - like 20% coolant? Freezing is not an issue.

 

As promised, here are some pics:

Radiator holds pressure fine and doesn’t leak at all, but obiously has seen better days. Considering soldering on a pitcock for a drain and an air line connection to a pressurized expansion tank (still haven't found one that fits).


Here’s a piece of what looks like latex paint or some kind of rubber – method of sealing??


Here’s the mounting for the radiator – as you can see, there is about zero room, especially for a shroud. The hood accually comes within a half inch of the water pump fan as it closes.

 

Well, I've been through this way too many times and I began to wonder if it's something more obvious. Unfortunately, I'm not able to easily test any changes since I live on the coast and it never gets hot here - 60 mile round trip on a hot day inland to determine what effects, if any, a given change will have.

After completely boiling out the radiator (lots of stuff came out) and reverse flushing with a hi volume of water (trapping the output for inspection), there is zero change - well, maybe a couple of degrees better at 215. This setup should run at under 200 at all ambient temps.

So I was looking to see if the under hood temps (thin wall headers, small compartment, etc) could be the contributing factor - looking at hood louvers. The trans cooler was/is mounted on the flat under the radiator and was/am considering removing the grill and mounting it up front and off to the passenger side as much as possible.

Well, in trying to figure out what the proper steps would be, I noticed that the front license plate hung down fully below the bumper and right in front of the central part of the radiator. It also extended toward the front of the engine right up to the main pulley.

Does it make sense to you guys that at 65 MPH that plate location would cause enough turbulence to keep the system from cooling properly? I’m going to remove it and move the trans cooler, but I’m wondering if, in the meantime, I should continue my search for the right hood louvers.

 

Did You check to see if the Electric Fan is actually pushing Air thru the Radiator and not pulling it thru ? The reason I ask is that most of these fans were designed to pull Air thru from the backside of the Radiator. If it is a puller and attached to the front of the Radiator it will be fighting the natural airflow at hi-way speeds. If this is the case , just reverse the polearity of the 2 wires at the motor and that "should" reverse the fan rotation. Check first never "***"ume anything.

 

It's a reversable fan from Summit - now that I think about it I never used the slip of paper to be sure of which way the air was moving. Got it torn apart moving the trans cooler, but I'll reconect the battery and test it just to be sure.

Many thanks for the reminder

 

Passed the paper test - fan blows toward the engine. Sure glad I didn't make that mistake.

 

Thanks for the rad pic, that helps explain what you have.
At this point, this is what I would do.
Solder a 3/8" air tube to the top drivers side of your rad where the cap normally goes. This will go to the upper feed of an external expansion tank. This external expansion tank will have a bottom "out port" that goes to the 1/2" port on the water pump. The purpose of this is to remove any air that accumulates in the radiator, allowing it and the coolant entering the engine to be air free. GM did it as well as many exotic car cooling designs.
Here is a pic of a vette radiator to show the tube.



Somewhere, somehow install an external expansion tank with a minimum 15lb cap. It should have an upper 3/8" feed tube and a 1/2" or 5/8" out tube. Lots of them available, but you may have to make your own or have one modified. The cap should be higher than the tstat elbow.
Then get rid of the funky cap setup on the tstat you presently have. It's not a preferred setup.

Your thoughts on the front grill and license plate are great, try them.
The hood vents are also on. The Viper uses them, The genuine Shelby mustangs of the 60s used them, anywhere, that had a congested engine compartment that restricted flow.
If you can't get the hot air out of the engine compartment, you can't get fresh air in thru the rad, pretty simple.
I had a Vega for a short period back in the 70s, don't remember which way the hood opened, but I thought it was hinged by the radiator. If it is you could just prop it open 5-6" by the windshield and see if the running temps improve, confirming the air flow.

That's just my opinion, but post your remedies and progress.

 

 

Neglected to say that I already installed the expansion tank and bleed tube at the top of the radiator - just as described above. I also tested the tub for air - I disconnected it from the tank and lowered it just a bit until a steady stream of coolant flowed out.

I had been hopeful that would fix the problem, but no help.

Currently in the process of moving the coolant overflow tank (making room for cold air intake) and the trans cooler from under the radiator/engine pulley to the area in front of the front passenger wheel well.

The hood hinges above the radiator and I'll be proping it open 5-6" next time out. The license plate/mount has been removed.

Here are a couple of photos from Summit of the louvers I'm considering. Emailed them for profile info/dimensions but they have not responded.




Both for early SS Chevys

 

There is front air dam and small splitter, that functions to force air into the rad. Perhaps the Vega lacks this feature?

 

OK, nearing the end of this saga and may end up with a new/rebuilt radiator... but there is one nagging detail that keeps coming back to haunt me.

Has anyone ever installed a cam one tooth off? What was the result of that error? Did the engine run well? What other anomalies were evident?

Don't know who built this 350, but early on I had the timing gearset open/off and it appeared to be ok - I actually removed the cam drive gear hoping that there would be some info about the grind/cut on the end. but no luck on that. The reason for removing the cover was a front seal leak.

Before reinstalling everything, I set number one piston to TDC and checke the dots.

 

I'm a little late to the party here, but have read all the replys and have myself had cooling problems with my corvette and some other cars I've had....I feel your pain.
From what you describe, I bet your rad is plugged up. I know you said your frustrated with rad shops, but you should try to find a small owner operated shop, and have him remove one of the end caps while your there, and you can see firsthand whats inside there. If its all plugged up, have him recore it.
If it's possible to first take the hood right off and go for a blast down the highway that could confirm or dispell an airflow problem.

Hope you find a solution....

 

The temp problem seemed to reach a new plateau today - with the ambient temp at 58 and overcast, the 2500 CFM electric fan going and the engine warmed up and then out for a 2 mile cruise, I returned, stopped in front of the garage and with the engine running at 2000, the temp started climbing from 197 (180 degree thermostat). Should never happen that way - the temp should have stayed below 190???

Have one more test to perform with an infrared meter to scan the fins looking for anomalous cold/hot spots.

Will pull the radiator and have it flow tested - if it tests bad, looks like I may have 3 options. Rod it, recore it or have a custom aluminum radiator made.

 

Did you try the temps driving with the hood propped up?

Just for fun, next time you have the coolant drained, pull the 2 1/4"npt block drain plugs. Will give you a good idea if the block is crudded up.

Post some picks of the new expansion tank and hoses setup.

 

Hey Noonie, I didn’t try the propped hood yesterday, but I also didn’t make a run inland where the temp was much hotter. It was 58 and overcast here on the coast and I would never have expected the temps to rise after a short run. Before I pull the radiator again, going to make one more test, hopefully this morning and I’ll prop the hood open.

Yesterday's test was with the vacuum advance removed – going to check the timing and if it is still as I last recorded it, I’ll reconnect the vacuum and try it again.

Here’s the expansion tank:



And here’s a recently installed gauge cluster:

 

Have looked for those engine plugs previously and never found them - looked again a minute ago and found a plug like allen head on the passenger side center near the pan, but couldn't see one on the other side??? Does the allen head fitting fit the description of what you know to be the drain plug?

FWIW, the freeze plugs appear fresh and newer - certainly not 40 years old. The engine was said to be built by Britco in WA state, so it is likely they boiled it out???

Thanks again,
Nick

 

I had a 71 v8 vega back in the late 70"s, 302 no electric fan, no hood vents, ran gm water pump and a flex fan. not a problem even thru the desert. how big is the motor bored, this could be a problem and try using one fan, get rid of the push fan. Have fun with the car, they are a blast!! by the way mooneyes makes a vert. tank that should fit

 

Good pics

I assume that copper elbow on the right of the exp tank is just a hose fill fitting.

While it's still roadworthy, try capping off the heater line from the expansion tank to the heater. That should prevent some hot coolant from bypassing the rad. And always record upper and lower rad port temps with each trail.

What brand and type of water pump is it?

Here is a pic of the pass side plug (brass hexhead)



And while I'm in Photobucket, here is the compartment hood vents in an original Shelby. A lot of cars had them including C3s, Vipers, new Ford trucks etc, so air extraction is somewhat important.



Racing Corvette

 

Thanks for that. Do you have a number or link for that radiator - assuming it's a vertical radiator you're referring to?