IMO - Your mechanic didn't help you out if this is a stock L-82 with A/C. I own a 79 l-82 with A/C and when the car was new it would freeze me in the summer in Las Vegas when it was 114 degrees outside. L-82 came with a HD 4 core radiator with a built in electric fan shroud that would kick in above some temp or when the A/C was going. Great big clutch fan that moves so much air when combined with the electric fan that it would be hard to duplicate the total cfm of air flow with two tiny 12 inchers. The stock system worked great. Is your chin spoiler in place and does the fan shroud bottom flapper work.

Aluminum radiator could be some thin 2 core or it could be a quality High HP unit like Dewitts... replacing the water pump is kinda dumb unless you get a higher flowing aluminum. As to thermostats. Was this mechanic smart enough to put in a high flow unit like a 190 or 195 and drill a 1/8th inch hole or two in it? lets the bubbles through and some water is always flowing.

So measure the radiator thickness and dimensions. In hotter climates it's also smarter to not have a radiator with built in tranny cooler. Run a separate big tranny cooler out front somewhere or with electric fan on the side vent.

 

mr. Gkull makes a good point or 2. There are Aluminium radiators and there are Aluminium radiators. The biggest rad you can shoehorn in there is the answer. 12 inch electric fans??? Made by who? Pushing how much air? High flow water pump without a highflow thermostat is like pissing up a rope. Incorrect timing specs and nothing will help!
time to find a better mechanic.

 

Maybe the OP will return .. i am sure all curious as to resolution.. i still am learning..
comment on L-82 w ac.. 4Sp anyway..
- electric fan as stated only for over temp..~235f?
- electric fan does not come on with AC but i wired mine to do so.
https://www.corvetteforum.com/forums...ss-option.html
- the clutch on my 4sp is certainly not heavy duty (probably to get a few more HP ?)
https://www.corvetteforum.com/forums...re-79-l82.html

 

The l82 fan has hd blades from Chevy.

I'm only going by memory, but I would hear my electric fan kicking on and I never remember my temperature gauge reading much over 200.

Or it would be on putting around in traffic and you could hear it cut off once you got out on the freeway and moving like over 55 mph

 

After all this great advice. Seems the OP has left the building 😣

 

He's getting actual coolant boiling, so legit has an overheating issue.

Exact accuracy of the gauge is a luxury to check at this point.

Adam

 

I can't member who wrote it, if it was Robert Shaw themselves, or Stewart, but I remember reading that with a high flow / high pressure capable water pump a traditional thermostat runs into the issue that the PRESSURE can cause the thermostat to delay opening and when they open is NOT ONLY based upon temperature but also pressure. The design of the Robert Shaw / EMP / Stewart thermostats are designed to equalize the pressure so that it's only the temperature that is driving when the thermostats open. (In addition to the flow benefits, you're getting flow starting and topping more accurately based upon temperature only.)

Stewart RECOMMENDS using the Shaw style high flow thermostat with all their water pumps but literally REQUIRES it for their Stage 2 and up pumps.

Every SBC should have one of these thermostats, IMHO, but definitely any one with a high flow pump with a modern impeller and tight clearances. This is the Robert Shaw thermostat modified by EMP / Stewart with the 3 3/16 bypass holes (180 deg version): https://www.summitracing.com/parts/emp-301
A no brainer for $37.

Ha! I found the language I was looking for; it looks like it's from Robert Shaw, but it's hosted on the Flowkooler website (which has the 180deg thernmostat without the 3/16" holes for $26.49, so save $10 and drill your own bypass hole(s) is another option): : https://flowkoolerwaterpumps.com/pro...ree-thermostat

Adam

 

Great point and very much the same one that Dewitt's makes in this article in which they say that you want to look at total Tube-to-fin contact by taking the # of tube times the width of the tubes as a way to evaluate one very important radiator performance-related spec: https://www.dewitts.com/blogs/news/1...etter-than-two

Many, but not all of the Chinese radiators will use .62" thick tubes; two row of these isn't very much tube-to-fin contact area. (The Champion 4 core, for example is a "4 core" but each of those cores has only .63" wide fins.
(Although the champ 3 row use wider .75" wide fins.

Dewitt's "Pro" Series use 1" wide tubes; the HP series 1.25" wide tubes.
The Cold Case C3 radiators use the same 2x 1.25" tubes and has teh same 2.5" of total tube to fin contact area, BUT use a strange and smaller tube inlet and outlet diameter for their hoses. (1.33" and 1.57") vs. Dewitt's 1.5" inlet and 1.75" outlets.
-I have to think you'll have less of a pressure drop / more flow through the Dewitt's and if you look at the bottom hose outlet sizes on C3 radiators over time, GM moved to the larger outlets over time, which I THINK helps to prevent cavitation / localized boiling from a big pressure drop right ahead of the water pump. (It should mean less risk of collapsing a radiator hose if you don't seek out one with the anti-collapse springs in them, too.)

I looked at a LOT of C3 radiators trying to save a few bucks and the Cold Case radiator definitely has nice wide tubes and provides the same tube-to-fin contact area, but I sure haven't found a cheaper radiator that even matches the statistical specs, even ignoring the quality question.

Adam

 

That looks just like the Milodon thermostat I've been using for years in both C3s. I guess it's a "Shaw Style"

I thought it just opened more. I didn't realize the stock-style $4- thermostat could stall closed. Wow. No wonder so many Bubba-style mechanics remove them entirely (which is still not best practice).

 

My friend had a similar problem with a Chevy 400 V8 engine. Turns out the distributor was in backwards.