Overheating Issues, Perplexed

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Originally Posted by Thoroco

My name is Dave Chapman from The Hollister Road Co the maker of the relay kit for the 2 speed Mark VIII fan mentioned above. I read through the posts on the overheating issues and can offer some basic suggestions.

First is that it doesn't matter if you have a 5000 CFM fan and a 10 row radiator if you can only get 3000 CFM out of the engine compartment. So air in has to be less than or equal to air out.

Next is the primary purpose of engine oil is to cool the engine by removing the heat created from the friction of moving parts. One of the best ways to reduce engine heat is by using an oil cooler either passive or fan cooled.

Third is the water must be able to be transfer the cylinder heat into the water and back out to the radiator and into the air in a reasonable manner. Straight water is not very good at heat transfer. Use a 50/50 mix of anti-freeze or use aftermarket products like Water Wetter Additive. They break the surface tension on the internal block areas so the heat will transfer to the water and again to the radiator. Anti-freeze will absorb more heat per pound than straight water before it gasses off or boils. You can also use a radiator mister that helps transfer the heat out of the radiator but that can get messy.

I haven't had my head under the hood of a Cobra since 67 but as I remember it was tightly packed with a 427 so it may well be the air can't get out of the compartment fast enough to let air past the radiator. You could also have air flowing around the fan assembly bypassing and not drawing through the fan shroud.
Tight motors make more heat so the oil cooler would be a good start in cooling down you motor.

I haven't really seen timing as an issue with overheating but I have seen very lean motors run hot. You may want to look at your jetting to see where you are. If you’re down in the low 60's high 50's then you might want to jet up a bit.

As for the Alernator being large enough to operate the Mark VIII or Taurus fans, 100 amps will do it oif yu don't have A/C or a big Audio system. The fans don't run off the alternator they run off the battery as do all the electrical components. The alernator is for charging the battery not running components. The test for that is disconnect the battery and everything will work for about 2 hours maybe longer, disconnect the battery and your alternator will burn up within 2 hours of use.

The big amp draw on the Mark VIII is miliseconds and its from dead stop to high speed. Starting on low doesn't have that issue and if you are using a 180 to start on low then you step through to a higher temp sensor like a 195 then your not starting from dead stop and the amp draw is reduced greatly. I have a 180 and a 195 on my truck and it cycles low speed on 180 to high speed 195 in traffic back to 180 and then off while on the Hiway. I'm using 60 amp relays that can take a 150 amp spike and 50 amp fuse that is a Slow Blow and takes the 100 amp millisceond spikes.

If I can answer any questions for you on cooling let me know. info@thoroco.com

Dave, Your 180 and 190 sensors, are they electric, exterior cap tube or designed to go into the coolant?

Dave