Overheating Issues, Perplexed

[mr0077]

Interesting tidbit of trivia on shrouds...during development of the C2 Corvette (the Stingray), the engineers found that the big block cars would overheat at high speeds. On that car, the air came through two openings below the front of the car, went up then back down through the radiator (that was leaned back at the top similar to some Cobras), then straight back toward the motor-driven fan. Because of the long nose and the engine setback, it had a shroud that was about 10" at the top and about 26" at the bottom. The engineers found that at high speeds the fan acted as a plate and would restrict air flow between the radiator and the fan. They came up with two fixes, one was shroud flaps that were pressure operated and the other was shroud flaps that were thermo operated...in either case, the flaps would open up to let air OUT of the shroud when needed for air flow and better cooling. Both ideas were nixed by the bean counters as unnecessarily expensive and complicated...

[Monster]

It appears that you have not applied the suggestions from a number of folks that have been through this issue, that your issue is AIRFLOW and that your problem appears to be an issue with the design of the shroud that you previously had installed. (not pulleys, t-stat,timing etc.)

Shroud's are a critical component in cooling, just look at any modern car. Not installing one reduces the effectiveness of your cooling system (especially at low speeds)

From SPAL:
The efficiency of your cooling system depends on the following factors:
Radiator core size (the size of the radiator inside the tanks where the cooling tubes and fins are located.) This space determines the diameter of the fan.
Space required for a cooling fan. Our High Performance cooling fans require 3.5-4.5-inches in depth (from the radiator core to the fan motor cap). This distance may be shorter if the cooling fan can be offset on the Radiator to clear the water pump.
Radiator material and number of cores. An aluminum radiator is more efficient than a copper radiator.
If a shroud is utilized: For the most efficient system a shroud should be utilized. The shroud forces the fan to pull air across the entire radiator core area, opposed to a fan without a shroud that pulls air only across the diameter of the fan.

Currently, without a shroud, in traffic (lower speeds) you do not have sufficient airflow going through your radiator. Air is only being drawn through the area directly in front of your puller fan. The area of your radiator according to what you posted earlier is approx. 393.75sq.inches and you have an 16" fan (201sq.in) which calculates to approx. 51% coverage/draw through your radiator.

As Olddog, 767jockey and Brettco observed the design of your "old" shrould appears to be an issue (not allowing sufficient draw). By increasing the space between the shroud and radiator to a minimum 1" at the outside edges and tapering to 2" at the fan you will increase the draw through the entire radiator which will improve airflow/cooling at both low and high speeds.

Try this, what do you have to lose at this point.

good luck,
Mike

[danc30]

I have the same radiator and fan set up as he does. I do not have a shroud. I have one of KC's big and nasty 482's and it hasn't gone north of 100C in the hot Florida sun and it was 95 last weekend when I took it out to the beach.....

I have the bypass hose hooked up just as it was when Keith built it, I have a 180 thermostat for a Ford with no holes drilled in it, straight water and a bottle of water-wetter.

I do have Cool-Flex hoses top and bottom, maybe that's it.

I believe it's in the engine set up myself. Waterpump, timing, T-stat, etc.

JMHO.....

I hope you can get this issue resolved though. It's probably something really simple and easy, you just need to find it.

Dan

[elmariachi]

Originally Posted by Monster

It appears that you have not applied the suggestions from a number of folks that have been through this issue, As Olddog, 767jockey and Brettco observed the design of your "old" shrould appears to be an issue (not allowing sufficient draw). By increasing the space between the shroud and radiator to a minimum 1" at the outside edges and tapering to 2" at the fan you will increase the draw through the entire radiator which will improve airflow/cooling at both low and high speeds.
Try this, what do you have to lose at this point.good luck,Mike

Mike, you might want to re-read this entire thread again. I have applied or am planning to try EVERY recommendation made except for going to 100% coolant and plugging the bypass valve. The prior is not even worth trying and the latter is on the list to be tried. I have been very systematic in my approach and SOME of the suggestions were tried repeatedly before I even made the first post. With regard to the flat aluminum shroud, it was installed as one of the things to try and solve the INITIAL overheating problem. After installing it, it caused more problems by making temps rise even while the car was moving. But after removing it, we are back to the original problem, which is the car is fine while moving and overheats slowly when is sitting still for more than 5 minutes. We did try spacing it back 1" and that made no difference, but that could be due to this shroud's design.

I recognize that this thread is getting long and some of you don't want to read it all. Just so everyone is clear on where we stand and what i am doing next in sequence:

**The car runs great and stays cool (180-185*F) while moving. The JEGS aluminum shroud screwed that up, both installed almost touching the back radiator surface and spaced 1-1.5" back from the radiator's back surface.

** The car slowly begins to overheat when sitting still for any period longer than 2-3 minutes. If I don't start moving, it will eventually hit 210F*+.

** The hottest I have let it get is 215F. Not going beyond that.

** I have backed off the initial timing from 20* to 16* and re-tuned the carb. Based on the plugs and vacuum gauge it is tuned correctly, but we won't know for sure until I get the cooling issue fixed and go hit the chassis dyno.

I am currently trying various sizes of restrictors, as recommended. Next step will be to try and plug the bypass as recommended. I am also chasing a smaller diameter water pump pulley, as recommended. Last steps will involve a different shroud/fan combo and finally, a new high-capacity radiator.

[DAVID GAGNARD]

El;

You've tried a whole bunch of things and some have helped and some have not, that's part of the process,been there/done that.....

I think your going about it the right way and I have been going over this in my mind and it's starting to get "personal" with me.

So far, you've done pretty much all the recommend "fix's" cept the pulley and a different fan.......pretty much the same results, so I'm gonna box up that crappy pulley and a fan and send to you to try....

The fan is 1/2 of a factory dual fan set-up off some Mitsubishi car I picked sometime ago at a body shop. The actual blades are 16"s in diameter and the whole thing is about 18"s in square.I cut it in half and used one half on my engine run-in stand, all I have is a small aluminum Griffin radiator (old) on the stand, maybe 24"s wide total. I ran my 331 race motor on it for a total of 3 hours a while back, with the longest continous run time of 1 hour at varouis rpms and it never,never got above 180.......On the race car I have a 17" or 18" electric fan (Spal, I think) but a bigger radiator and it does the job. I think it is a 3600 cfm fan, but the Mitsubishi fan will blow that and at least half that again if not more, it's a freakin hurricane when on, I'm guessing at least 5000 cfms...

It's worth a try and by switching the hot/ground wires, you can make it a puller or pusher....

E-mail me your mailing address at

cda351@bellsouth.net

and I'll get it out to you in the next day or two.....if it works, pay the shipping and it's yours.......
As I said, it's starting to get personal with me and I want to see it fixed as bad as you, been in the same situation before and I know it ain't no fun going for a drive wondering when it'll get hot and always watching the temp gauge!!!!!!!!!!

David

[elmariachi]

Originally Posted by ERA Chas

El,My So acts exactly as yours before your testing: T'stat opens at 180, temps while moving remain 180-190 (6000+ RPM) slowly inching up to 210+ standing still. . This has been the case for 17 years and I've lived with it and driven accordingly.

Charles, you bring up a good point. This is not a catastrophic problem here, especially after Patrick having jelped me work out a better level of timing and tuning last week. Its more a matter of me having peace-of-mind that no matter the situation, I am not putting the engine in danger of melting down. Houston is a BRUTALLY hot environment 9-10 months out of the year and I don't want to ever worry unless I have to. As Charles has done, I "could" manage this if I had to. But only after I exhaust all fan/pulley/shroud/radiator options. Besides, I love a good challenge.

Originally Posted by DAVID GAGNARD

I think your going about it the right way and I have been going over this in my mind and it's starting to get "personal" with me.David

Well I love the support and sponsorship, but don't lose any sleep over this guys. David, hold off sending anything, I did score the 5.5" water pump pulley. I already had the larger 7" crank pulley so I am going from 6.5" on each to 7"/5.5." That should be a big change. And I have the 2700 cfm SPAL fan that I had on before this 3650 cfm. I am going to install the pulleys tomorrow eve and play with various locations front and back for the spal fan. I also have a HUGE shop fan that I borrowed to set in front of the nose. And I also located a dual puller in a plastic shroud that is supposed to pull 5000 cfm that I can borrow this weekend. Let me try some of these items next and we'll see what happens.

Thanks guys, more to follow.

[ERA Chas]

Originally Posted by elmariachi

Charles, you bring up a good point. This is not a catastrophic problem here, especially after Patrick having jelped me work out a better level of timing and tuning last week. Its more a matter of me having peace-of-mind that no matter the situation, I am not putting the engine in danger of melting down. Houston is a BRUTALLY hot environment 9-10 months out of the year and I don't want to ever worry unless I have to. As Charles has done, I "could" manage this if I had to. But only after I exhaust all fan/pulley/shroud/radiator options. Besides, I love a good challenge.

To be clear, I'm not encouraging you to 'suffer through it' as I do. You need to do this in your environment.
I too like to track things down to a satisfactory conclusion.
You go guy!