Fast Monty Shroud
 

There's been a lot of cooling discussions here about shrouds, fans, radiators etc.

I decided recently I wanted to try one of Mike's shrouds after I started having some cooling issues with my previous setup.

That previous setup was a Cold Case CHC11 radiator with a Flex-a-Lite Black Magic 180 fan. This was all in front of a 580hp 465.

Full context, I did end up replacing the radiator with this change, so I can't give everything a 100% apples to apples comparison. My original CHC11 sprung two small leaks from the upper portion of the end tanks. Likely because I accidentally smacked the core with the engine when I was installing it last. I had cured that leak with a few Bars stop leak tablets, but ever since I did that, the system wouldn't cool as efficiently.

I finally hit 225 degrees in stop and go traffic in 90 degree weather and that was my impetuous to get this changed.

So what did I do? Basically, everything.

New CHC11 radiator from Cold Case
Fast Monty's dual 14" fan shroud
Dual Maradyne M142 fans
Big 3 wiring upgrade
Robert Shaw 180 degree stat
New AC Delco Upper and Lower hoses
New heater core hoses

My car with the previous setup has always run 195 on the highway, and would run about 205 in slow moving main street style cruising. In true stop and go traffic, or idling, it would slowly creep to 210 before leveling off.

With this new setup, also in 90+ degree heat, the engine now runs on the stat on the highway. In that slow moving main street cruise type situation, I observed nearly 15 degree cooling reduction, with the system running right at 190.

The idle creep is still there, but dramatically slowed. It now takes roughly 15 minutes of loaded idle time (in drive, on the brakes) to reach 210 degrees. If the car is put in park, it slows that time down even further. If the hood is opened, the fans pull the temps down to below fan off threshold of 183 degrees.

So, what is this telling me? By and large this radiator/fan/shroud combination is doing everything it's supposed to be doing. The hood open behavior leads me to believe I have a heat soak issue related to air under the hood. When the car is moving, even a little, the hot air is being evacuated. When stopped, it's building under the hood and finding place in front of the radiator to move, causing a loss of cooling efficiency.

Through a bit of research, it's also possible my water pump may be partly to blame. I am running a PRW aluminum performance pump with the 6" AC pulley. This pump is somewhat designed for higher rpm use and may give up some flow at idle and low engine speeds. It's designed to shine above 3500 rpm for sustained periods.

For my car that spends most of it's life cruising around, the Flowkooler may have been a better choice as it's designed around providing better low speed coolant flow.

I'm testing some additional idle RPM to see if that has any effect. I may look at other remediation measures such as hood vents as well.

Anyhow, I'm pretty stoked on this setup. The install looks nice as well compared to the old Flex-a-Lite fan which always kind of looked like an afterthought.

Attachment 673039

I also use a PRW ali water pump with a stock 3 core radiator and a flex fan in my '72 Lemans. The car has a hard time getting to 180F in 90+ weather highway or idling. I don't think it is stagnant air that is the cause of your issue. In my race car, I use a generic ali radiator with a Mark VIII E fan ans a Meziere E water pump. Runs 180, gets to 200 at the end of the track and is back to 180 in the pits.

Mine is actually the opposite. I haven't been able to hot-rod this engine enough to make the temperature rise.

It used to be the slower and lower RPM I drove at, the warmer it would run.

I added 50 idle rpm and that seemed to have actually helped a bit.

Assuming the stock core dimensions are roughly the same as the Cold Case numbers, Lemans radiator probably has about 30% more frontal cooling surface area compared to the 1st gen Fbody. That solves a lot of problems.

My Fairlane race car as a 503 ci engine with a cheap ebay special 1" thick core radiator for a like 84 F250. But its got a huge front surface. It keeps the BBF cool even with two 12" fans just ziptied to it with no shroud.

My 67 on the other hand has been a battle, and it has the same nice Cold Case radiator the OP mentioned. You are just limited to a somewhat small radiator in those.

FWIW I also think I have my cooling solved with the junkyard PWM fan swap I did. Big 18" single PWM out of a volvo XC90. Its been in for over a year and I dont think Ive seen a number that starts with a 2 since. I have to admit that your setup is way prettier though :)

Mine mostly sits right at the 180* thermostat, but once in a while it will creep up to like 185-187 with seemingly no difference in inputs.....that irritates me. I dont like not knowing why something is happening.

Frontal area is a large consideration. There's a reason the 2nd gen F-body went to an A-Body sized radiator. The brunt of the cooling efficiency happens in the first core of the radiator, so the larger you make the front face, the more cooling you receive. The extra water capacity is helping quite a bit as well.

This seems like a low speed air flow issue, what is the cfm rating for your fan? The Mark VIII is supposedly 4400 cfm.

Each fan is rated by Maradyne at 2135cfm. As tested by mike in a controlled manner, loaded with a radiator in front, they pull about 1500cfm each. I'm unsure what the loaded cfm of a mark 8 fan is. But it's likely comparable to my current fans in total cfm.

I'll have the car out for a bit in 100 degree temps this weekend. So far, that small rpm bump at idle does seem to have helped. I'm never leaving the car idling anywhere for 15+ minutes anyway, so it's somewhat of a non-issue. Just transparent about what this setup is and is not doing.

Thanks for the info, very helpful.

The Mark VIII is not 4,400. Maybe 3,200 on its absolute best best day, if that, I believe others have shown.

Hope FMG will test a 1990s Mark VIII fan as there are repops of it for $85 on RockAuto that should suffice for a test.

Could be the difference between unloaded and loaded testing. As FMG has pointed out thoroughly is that many people test these things inaccurately by just placing an anemometer right up against the fan where you can get big turbulent spikes in airflow.

Whether it's 3200 or 4400 cfm it works so I'm happy.

I still run the FoMoCo (cough cough) Mark VIII fan too on a car... but I see a new current GM 19" version electric fan that is what nearly every custom builder is putting on their radiators lately. Hopefully Mike can test that one as well....

Love the write up... and yes, I'd love to test the supposed monster CFM Mark VIII... can someone get me a part number? please email me FastMontysGarage at gmail. Thanks all!

Pretty sure that's the C7Z06 fan. I believe it's a 600 watt brushless fan. That's some pretty serious wattage.

The price was just too much at close to $500.00 per fan, but the FMG shroud does also fit this bad boy. https://www.spal.com/it/-/30107107-v...320p-r-a-n-94a

1000 watts in dual configuration. In Mike's testing he saw loaded CFM per fan at or above 2000cfm.

Sorry I was wrong -- it is this Vintage Air fan 850W assembly most high end builders are using not a GM unit:

https://vintageair.com/additional-op...s-and-shrouds/

[QUOTE=JLMounce;6623488]Pretty sure that's the C7Z06 fan. I believe it's a 600 watt brushless fan. That's some pretty serious wattage.

This sure is worthy for your 1969:


https://vintageair.com/monster-1967-...hless-fan-kit/

That's a big ass fan.

Thats pretty close to what the Volvo fan I swapped in is. Its often called a 19, but really its more like 18.5.

https://www.240turbo.com/BrushlessFans.html

There is a ton of good information in this link, including the Vintage Air fan listed. They also have the XC90 Bosch fan I used, which is available in all kinds of things. I have the same fan in a shroud for like a 2005 Mercedes SL500. This is where I started when I put together my swap. Of course I have a terminator X which made my life easier on the controller side.

If I was going to pay the aftermarket price for a big PWM single fan, I think its hard to beat the DeltaPAG package because it comes with the brushless controller.

Yeah, my setup since it's triggered by a FiTech 30001 is on/off. You can of course wire the brushless deals to behave that way, but you miss out on the whole PWM thing for ramping in voltage on an as needed basis.

It's always going to be better for the engine, performance and efficiency to be able to keep a constant temperature vs swings up and down like an on/off system will create.

While all the "Mods" are interesting, and fast monty has some ideas as a auto plumber, a New pattern COPPER Cold Case will cool better than aluminum.
Also the 421 Mod will eliminate the need for electric fans..... fact..
The aftermarket has won the marketing battle with Plastic and aluminum, and bigger alternators, and bigger wires.... That said...
https://forums.maxperformanceinc.com...7&d=1783913183

It is absolutely true that copper is a better heat conductor than aluminum. That's not the whole story though.

On a brass/copper radiator, the copper fins have to be attached to the brass tubes. That's done with either solder or brazing depending on the construction methods. This creates a thermal choke point that diminishes the heat transfer from the fins to the tubes and thus into the coolant. Because the solder or brazing process introduces extra material between the fins, this also means the fin counts are necessarily less. As the radiator sees pressure build, the tube sizes are also limited because due to ballooning of the soft tubes. This means you need to stack additional cores to reach enough surface area. What gains you get from using the superior thermal conductivity of copper is reduced by how the unit is manufactured.

Aluminum radiators are constructed using controlled atmosphere brazing, which eliminates that thermal choke point. Aluminum being stronger also allows for larger tubes and tighter fin counts without external brazing alloy or soft solder that reduces fin count.

Point being, you can find brass and copper radiators the same as you can find aluminum radiators, but in comparable price points, I wouldn't expect the copper/brass unit to cool as well because it's likely constructed with soft solder. Even the more expensive units (some as much as $1500 for just the radiator) are still using silver alloy brazing material, that again creates a thermal choke below the heat transfer rate of an aluminum unit. There's a reason OEM's don't use copper/brass radiators any longer. For the needed cooling capacity, they are more expensive, heavier and take up more space.

As far as the fans are concerned, your radiator doesn't know how is in front or behind it. If you need 3000cfm to cool your engine, doing so with an electric fan or mechanical fan doesn't matter, just as long as you get there.

I can tell you, this is the best my car has ever cooled itself. It's still not perfect and I've always had a slight to moderate idle heating problem. I've had everything now from a factory shroud with copper 3 core radiator and the factory 19" flex fan, an aluminum radiator with a single 15" electric fan and now another aluminum with dual 14" electric fans.

I had the car out in 101 degree heat this weekend and the setup ran at or below 190 while moving, but did see increased time to creep at idle. Still not enough to really be worried about unless I got caught in a sustained traffic jam. This is what's working for me. If you prefer mechanical fans and copper/brass radiators and those are working for you, that's great.

Curious how much of the heat at idle is coming off your transmission/converter? If you dump any of that under the hood, it may be a contributor?

I have a large derale cooler (passive only) that is mounted in front of the radiator. It likely has some type of an effect as it's heating air prior to entry to the radiator core in that area. But it's not dumping that heat into the engine bay itself.

I had this same issue previously with a much smaller trans cooler that was mounted out of the way of the core. That was with a more stock type setup with a TH400 and mild converter.

Since I've been in solve mode for the idle creep specifically, I've been looking at some smaller details such as radiator seals. My car in the entirety of my ownership has never had the radiator seals in the front that seal up from the frame horns to the core support. Nor has it had the inner fender splash shields, or the rear hood seal. My research on this is limited and there's not much out there on testimonials, but if the stock cooling system was designed around having those in place and forcing hot air to travel down, under the trans tunnel and beneath the car, I may be inhibiting that flow.

The altitude I run the car at (between 4500-5000ft) has a minor effect as there's less atmosphere to actually carry heat away, but really I'm chipping away at the edges now.

Thanks...just a thought.

The shrouds you are missing sound like good intuition!

Do you have a way to monitor the temperature of your trans fluid?

I had to add a cooler to our truck when I found out how hot the tranny got when pushing a small camper around the yard. I had no appreciation for the heat generated before this educational experience.

I also learned there was a thermostat in the trans that let the heat climb too much before allowing the fluid to circulate to the cooler. Dealer had a service bulletin and replaced with a lower-temp stat. Not the same as yours but there's a LOT of heat that has to go somewhere..

It's a bit of a pain because of where I have my trans computer located, but yes I can monitor temperature. I don't know what it runs in 100 degree heat, but average temps I usually see if I'm datalogging the trans, or outright viewing the controller ranges from 155-170 depending on what I'm doing.

The fact that this is a lockup converter, helps with heat quite a bit. It's definitely hottest in slow moving traffic where I'm on and off the throttle without the converter being locked up.

[QUOTE=JLMounce;6623880]It's a bit of a pain because of where I have my trans computer located, but yes I can monitor temperature.


I say time for a 5 speed and watch your temps drop 5-10 degrees ;-)

Hah, don't tempt me!