thoughts on cooling


Well-Known Member
Regarding the Circle Track hose modifications, I found some FANTASTIC additional details on WHY this is a good idea from Stewart Components:

They ultimately clarify that one of the prime reasons that this can be beneficial is that aluminum head's generally have thicker decks and thicker upper head deck areas, and larger ports and that the area of the head that then gets neglected is the internal head coolant passages. They ultimately end up considerably smaller than on OEM iron heads, which makes getting enough flow through the heads difficult.

"SBC race engines with aluminum cylinder heads usually require extensive external plumbing to address two design problems:

  1. Aluminum heads have much smaller water jackets than cast-iron heads because the external dimensions are similar, but the ports are usually larger, the deck is thicker, and the material near the rocker stands is thicker, all leaving less area in the water jackets. This decreased internal area leaves less area in the water jackets.
  2. The siamese center exhaust ports are a design compromise that presents additional problems when aluminum heads are used. The area near the center exhaust valves is thicker, thus allowing providing less surface area for cooling.
We recommend installing a pair of –10 AN lines that connect the rear of the aluminum cylinder heads to the thermostat housing crossover in the front. This step will help offset the smaller water jackets. A pair of -10AN lines connecting the pressure side of the water pump with the area in the center of the cylinder head (just below the exhaust ports) will offset the lack of surface area due to the extra material."

I feel like these modifications finally make more sense to me.
The Stewart Water pumps (Stage2 and higher) , which are HIGHLY used and respected in the circle track community all come with built-in bosses for adding AN lines (some of the Stage4 water pumps already come with the AN fittings plumbed in).

Stewart's 5 Tech Tips are just an incredibly boiled down list of great cooling tips and myth busting, most of which have already been covered in this thread.

I think it's also worth noting that most of the manufacturers of high performance SBC water pumps (Stewart, Adams Performance, and FlowKooler), either REQUIRE the use of RobertShaw thermostats when using their pumps, or require it when using their higher-end, better flowing pumps but ALWAYS RECOMMEND them.

-These companies (Stewart and Adams) actually do CFD 3D simulations on cooling systems for folks like NASCAR, and they're recommending RobertShaw thermostats; personally, I think it's silly to run anything else.



solid fixture here in the forum
HMMM... I don't have any anodes in my system right now... Probably need to find somewhere to put them. Unfortunately when I got my intake ceramic coated they didn't mask off the threads and it makes screwing anything into and removing anything from my intake's coolant ports very risky as sometimes things "stick" to the threads and just rip out and totally wreck the threads. I'll need to find somewhere else either on the block's cooling jacket or on the radiator, or the plug that sticks out the top of my water pump, I think for a Vortec-style recirculation line...

Use a tap or thread chaser on the aluminum intake.


Well-Known Member
From Stewart: An example of the impact of water's higher specific heat vs. ethylene glycol or propylene glycol mixes:

On a typical engine with a coolant flow rate of 100 GPM and an energy loss through the cooling system of 189.5 HP, water would need to gain only 10° F, Ethylene Glycol/water mix would gain 20° F, and Propylene Glycol would gain 33.3° F.

A 75/25 water to ethylene glycol blend in the same situation would see a 15F temp gain from the engine inlet to the outlet.
-You have to run higher flow rates with higher percentages of coolant for the same cooling capacity to make up for the difference in reduced specific heat.

A 50/50 Ethylene Glycol mix has a 20% decreased specific heat @ 36F vs. pure water and 17% less than pure water at 200F.

Pure water is also less viscous vs. a 50/50 blend and should flow slightly more; increased speed through the radiator also increase TURBULENCE which is important to the efficiency of the heat transfer from the liquid to the air, too.

Stewart also posts a great table showing the pressures at each part of a Winston Cup SBC engine (likely running their stage 4 water pump):
Anywhere there is a restriction in flow the pressure goes up, which isn't all bad, as it increases the boiling point at that part of the engine, too.

This is assuming a 100GM water pump flow (I'm not sure whether this is an SB2 cooling setup with the water inlet going into the center of the lower block via the freeze plugs as the inlet or a traditional front-of-the-block inlet cooling system, though:

Lower radiator hose = 1.5 PSI
Block and cylinder head - each (at 50 GPM) = 8.5
Outlet manifolding = 1.25
Top radiator hose = 2.25
Radiator = 1.5
Total = 15.00 PSI

-For me it's interesting to see that the overwhelming majority of the pressure increase happens as the coolant flows through the restriction that is the heads, but that's obviously where you actually most NEED that pressure. From the earlier-in-the-thread discussion about running coolant bypass hoses from the water pump pressure side to between the two center exhaust ports in an SBC and / or running hoses from the rear of the intake to under the thermostat, that SHOULD increase flow at the major restriction, but likely at the loss of SOME pressure. (So the pressure data seems to confirm that if you want to gain flow that's the place to do it.)

I also think it's interesting that the Top Radiator hose is the place of the 2nd largest coolant restriction as I've heard before that manufacturers specifically create a slight restriction there to keep the pressure slightly higher in the engine to avoid coolant boiling, so I think that pressure increase is "by design". You also tend to almost always see larger radiator hoses going into the water pump vs. coming out of the engine as that helps to reduce the amount of vacuum / pressure drop going into the water pump, which helps to reduce the likelihood of cavitation.

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Dewitts, a US MFGR of Radiators, very well known in the Corvette community, has a great blog post that explains the importance of total tube-to-fin area to radiator performance and that sometimes, when you have really wide individual tubes, a 2 core radiator can cool better than a 3 core radiator or a 3 core vs. a 4 core and you really need to take the time to evaluate the total tube-to-fin area:

Some cheaper imported radiator cores are made with only .062" wide tubes, but .075", .100", and even .125" wide tubes exist and the wider tubes will expose more area to the cooling airflow and cool better.

Ultimately Tom Dewitt recommends taking the tube width x the # of rows to determine the total tube-to-fin area.

A few real examples for some C3 Corvette radiators:

Pro Series for 77-82 Corvettes: 1" wide tubes x 2 rows = 2" tube-to-fin area
HP Series (highest perf) for 77-82 Corvettes: 1.25" wide tubes x 2 rows = 2.5" tube-to-fin area

I'm sure many of the ultra cheap imported cores have the .062" wide tubes, but below I'm looking at two of the more popular and good rated off-shore radiators for comparison; you only get into the thinner tube widths when moving to the 4 row radiator

2 Row: .75" wide tubes x 2 rows =1.5" tube-to-fin area
3 Row: .75" wide tubes x 3 rows = 2.25" tube-to-fin area .25" more than the Dewitts Pro series for $245
4 Row: .63" wide tubes x 4 rows = 2.52" tube-to-fin area .02" more than the Dewitts HP series -$295
-The Champions do NOT work unmodified stock rad cushions and require trimming them to the right size and profile; NOT a direct fit.

Cold Case:
CHV718A: 2 Rows with the same 1.25" wide tubes x 2 rows as the Dewitts HP series and corrugated fins @ 16 fins per inch like the Dewitt. = 2.5" tube-to-fin area.($417.55 vs the $990 for the Dewitts HP series)
-These are reported has being direct fit and working with stock-style cushions. (Assuming you're replacing a stock 3" thick radiator)

These Cold Case radiators seem to be just fantastic amounts of cooling for the price. I wish I knew more of this stuff back when I purchased my Champion 3 Row, but for the money I'm still happy with the Champion; but if I could go back in time I'd pay more for the Cold Case.

I'm posting some real-world examples, but I think paying attention to the tube-to-fin area and whether the fins are flat or corrugated can help make pretty informed decisions on what the radiator performance will be like AND to identify cost-savings opportunities.

-I think there's some improvements that have been made to copper radiators over the years that are worth talking about at some point later, too...



Well-Known Member
Even when you use an Anti-Seize ? How about using an anti-seize and thread cleaner tap, run that thru there a several times before installing the anode
Sorry, somehow I forgot to respond to this one. My memory on it isn't great as this was over a year ago now, but I want to say that it seized up without anti-seize but with the red thread goop stuff that often comes on the coolant temp sensors. -The ceramic thermal barrier seemed to act like "super seize" even finger tight threading something into those threads nearly instantly seized up.

Most of the thermal barrier self-coating companies recommend taping off any / all threads prior to getting whatever coated, I guess I learned why the hard way.



Well-Known Member
I got back from vacation Saturday night and both my zinc anode and lower radiator hose with the stainless spring install had showed up.

Installed the zinc anode in the bottom drain for the radiator; probably the worst place to be able to check on it over time, but I'll check the fluid with my pH meter.

The GM "correct" lower radiator hose was only available from specialty Corvette shops; I had previously purchased a silicone hose for "engine dress up" reasons, but I didn't realize just how thin and "squeezable" it was going to be, nor that they continue to slowly sweat coolant out through them. The GM lower radiator hose is significantly thicker and less squeezeable than the silicone lower hose even without the stainless spring. With my high flow water pump, I was afraid of collapsing the lower hose under acceleration as a C3 buddy had just posted a video of his lower (rubber) radiator hose collapsing when he blipped the throttle quickly.

My cooling system is now complete unless I manage to find the 3,000 stall TC that I'd really LIKE to have in the car for a deal; if that happens I'll have to install a dedicated trans cooler but right now with my 2,400-2,600 RPM TC stall (lockup), I'm comfortable using the stock cooling coil built into the radiator. I know a lower trans temp = longer life, but my 4L60e has a temp probe installed so I can track the temps and if they get over 190F, then I'll switch to a dedicated cooler either way; the stock setup is just too easy to argue with for now.