Is the radiator cap on the t-stat housing just a regular radiator cap? Could you connect it to an overflow container? (the vega probably came with one stock, you could use it.) Have you given any thought to getting rid of the electric pusher fan and using a shroud on the back of the radiator? I have a feeling your problem may be more about airflow through the radiator than anything else. Is there any way for air to get around the radiator?

In your first post you said the overheating happens on the highway. The pusher electric fan may be impeding airflow through the radiator. Is there a hood scoop that is not sealed to an airbox of some kind? If you don't have some way of generating a low pressure area in the engine compartment, airflow through the radiator will suffer on the highway.

Scott

 

The Vega's all came with 80*+HP 4-bangers (except the Cosworth) - this Vega came to me with the 350/converted and with issues that I'm fixing.

The cap you see in the photo is a cap I have modified. The regular cap is 10 lbs. and I have not known it to blow coolant since I had the radiator repaired.

The overheating I referred to was more like "higher than I like to see it on the highway" (215-220), never blowing steam or coolant. There is no room for a standard/custom shroud, at least not one that goes all the way around.

The electric fan comes on at 165 and is always on - 2500CFM. I'm guessing that the plastic mechanical fan on the water pump is primarily creating turbulence. It is my understanding that at highway speeds no fan is really required, but both fans are always on in this situation.

At this point, I'm guessing the high heat is too much advance (have not tried it without the vacuum advance - can't say why I have overlooked that one) combined with air in the cooling system. This engine at 2500 RPM is creating 50 degrees of advance with the vacuum.

It's on my list to run it with the air out of the coolant and then to run it with the vacuum disconnected. The problem is I live out on the coast and there are no 60+ long stretches of highway out here.

I'll get this figured out sooner or later and I'll definitely post the fix...


Nick

 

Here's a pic of the beast - probably 400HP.. Now has a posi with 3.73's DOT drag radial, CAI and more. Weighs in at 2800 and is not quite up to my ZR1's performance.

 

V8 Vegas are cool. Well done V8 Vegas are really cool! You used to see them quite a bit, back in the day. Not so much anymore. A friend of mine had one in High School. What a wickedly-fast, evil-handling thing it was, too! Come to think of it, that probably has a lot to do with why you don't see 'em much anymore........ Good luck with your project,

Scott

 

That's a very typical number, not the source of your problem.

 

Did the sending unit come with the gauges? I always wanted a v8 vega, i had a v8 monza once.

 

Did the sending unit come with the gauges? I always wanted a v8 vega, i had a v8 monza once. Thats a good looking car. Did you conect the sub frame, hell im not even sure, is it a unabody?

 

Definitely a unabody - the coversion was done when I got it. I'm just trying to make it work properly and it's turned into a real project.

 

Well, I’m shooting at a target with inconclusive bullets – LOL. After all my testing it appears that the radiator may not be flowing freely. It’s vintage corvette 4-core brass, that may have seen better days. Thought about replacing it early on, but couldn’t find an off the shelf new one that would work.

Here’s where I am with my testing. After feeling confident that I have removed all the air, I disconnected the vacuum advance and drove the beast into town. Living on the coast with normal temps in the low 60’s, it’s hard to test an engine that runs hot. It really never overheats with coolant all over the place even when shut down at 220 with the fan running (except after running the traps at Sonoma Raceway – aka Infineon). When I head inland and the temps get into the high 70’s, the engine temp seems to follow the ambient temps and starts to increase and when I finally get to the freeway the engine is running a 215-220 temp. The electric fan helps when I turn it off I can get the temp back to 200 or less in a very short time.

As I head back to the coast, the engine temp comes back to under 200, as it did yesterday. So when I got back I let the engine cool down to the point where I could safely open the radiator cap (it’s not on the radiator, it’s on the thermostat housing and it’s the highest point in the cooling system – see pic above). With the cap off, I started the engine and at idle the coolant immediately bubbled out of the housing. So I guess I need to find out what to do about the radiator.

My thought was to rig up a tight garden hose connection and see if I any sediment come out into a collection pan, or I can take a chance and have it boiled out, or I can have it re-cored. Open to some thoughts here.

Oh, and after it started bubbling over and just after I turned the engine, I tested the accuracy of the dash gauge by comparing the infrared reading of the coolant at the housing – was within 2 degrees at 173.

Thanks again you guys,

Nick

 

Still looking for an expansion tank that will fit. There's not much room under the hood on the beast.

 

Is the top of the radiator higher than the fill cap? Vented or closed system (maybe I missed it).
Some clever use of sheet alum in front of the radiator/under the core support to direct air in may help. Cant really tell if youd need it or not


Tried the infrared gun thing too.
Closest thing to being accurate was being pointed directly on the fins themselves
When pointed at anything else the coolant was at least 30 deg warmer the pointer only measures the surface temp not inside em.

 

Post a pic of your radiator (out of the car) or a google image of a similar one.

 

So the vacuum advance was disconnected the entire time?

 

Was searching around this morning and found this similarly sized one.



Imagine an older brass capped unit that is configured like it but without the radiator cap.

 

The top of the radiator is below the top of the cap on the thermostat housing. There is very little room for air/expansion. Remember, there is a 2500 cfm electric pusher fan on the front of the radiator.

Maybe a cooking thermometer dipped into the coolant??

 

Yes the vacuum was off/plugged on the entire trip/test.

 

About to remove the radiator for the 4th time in 8 months. Have done some more searching and found the following considerations:If either of those two are not true, especially No. 1, there will be heating problems directly related to the radiator.

This radiator is obviously older and while it appears to my untrained eye to be in good shape, I have nothing empirical to determine how it is functioning.

I did find a very basic test that goes like this:Also, I found another test that indicates a problem if there is backpressure forming in the radiator at speed. Watching the temp gauge, you will notice that the temp drops a bit just as the thermostat opens. When that happens, check the firmness of the radiator inlet hose at 2500 – 3000 rpm – that hose should be fairly easy to squeeze at that temp and should not immediately firm up at a higher rpm.

This hose failed that test and the firmness fluctuated with the rpm.

Let me know if you have any thoughts in this regard – BEFORE I REMOVE THE RADIATOR again. LOL

 

Those tests are vague at best and too many variables involved to be conclusive.
Bottom line is you must have the radiator cool the coolant or remove the heat from it or however you want to term the process.
Simple test.
Set the engine to run at 2000 rpm, preferably have a strong fan aiming at the grill intake, use a IR gun to shoot the metal inlet tube (top) of the radiator and then shoot the outlet metal tube (bottom) of the radiator. Temp at the bottom should be 20-30° cooler than the top. I suggest you use a 195° tstat for this. That's the only test you need perform.
If you have access, you can also shoot for cold spots on the tubes themselves to look for blocked flow.
When using an IR gun, hold it as close to the target as possible (1") and preferably a non reflective metal surface. If you don't have access to the top or bottom tubes, then shoot the tstat metal housing for the top and the large intake port directly on the water pump for the bottom.

The biggest variable for radiator cooling is the ambient temp (as you discovered driving coastal vs inland) and the next is the amount and speed of air contacting the radiator tubes.
Next is the velocity of the coolant flow, different than gpm. This is why higher efficiency radiators have more tubes with smaller internal openings.
This is also one of several reasons why higher flow water pumps cool better.

Before removing the radiator. I would do a serious cleaning of the engine and rad internally, using the block plugs as drains. It's a real PITA to do thoroughly, but it lessens one possible problem. Here is a link with more links included and the source of a good product to use.

http://forums.corvetteforum.com/1583704073-post4.html

BTW, your mechanical timing is good enough for cooling efficiency and using full vacuum at the vac can will help idle temps and slightly at cruise with a marginal system.

If and when you remove your rad, post pics of it, your front grill area and your fan(s) etc.

 

Too late - pulled the radiator already.
Did a reverse flush with a garden hose and the radiator on the ground. Also ran the gravity test and it was pouring out at about 12 GPM at first along with a huge amount of debris (scale, calcium/lime) two chunks of latex?? like paint also came out. The sediment continued to come out though less and less. At the end it was flowing better at 18 gpm but I think it needs more work.

The coolant has always looked clear when you open the cap so the system is not totally rusted like some I've seen and read about.

At this point, I was thinking that I would fill the radiator with a 50/50 solution of white vinegar and water and let it set for an hour or so and then drain it, check for sediment and flush. And perhaps repeat.

Comments?

I would take it to a a radiator shop, but I've had my fill of those guys. It's hard to trust anything they say.

If it comes down to taking it to a shop, I'm buying a new one.

Will post some pics tomorrow.

 

takeing the cap off makes it boil that's why u have a cap it lowers the boiling point