I dont care how long you leave your fans on.You should never blow a fuse or melt any wires.You should be able to turn the fans on manually with car off and run them till the battery dies without any problem.I think your answering your own ? with the temp going back down while driving-not enough air flow at idle.Take the fans off put your stock fan back on im assuming is a clutch fan-or put on a flex fan.I would still run electric fans but in front of radiator-(pusher)

 

rebc3,

I have nearly the same setup in my '70. My engine specs are:383, Dart Pro1 heads, 250d@.050" .540 lift, 10.5 compression, Accel DFI Gen 7. I'm running the copper big block radiator with the Dual Flexalite fans. I was at the Kool April cruise Friday nite and ran in traffic for 2hours. It never got above 190 degrees. I'm running a 25 amp fuse on the line to the fans. The DFI is controlling the fans thru a relay. I ran 10 gauge wire to the relay and the fans. I think you have the right components, but something is wrong in the execution.

Bob

 

the msd pro billit has two timing curve adjusters on the printed circuit board. one for mech. advance, one for vac. advance. i set them both at zero. this combo works great for me. i had this cooling issue before when i used the mallory hei style dist. also. and believe me, with the timing tables i have available to me ive tried a few. the problem still exists. im not so ignorant to know that it still could be a timing thing but i dont think so. this thing runs like a raped ape.

im thinking that i should switch to a 195 stat or just ditch the fans. theve been nothing but trouble. blown fuses, melted wires, cooked control box i had to replace. im not having any luck with the e-fans
also my oil temp gauge says im running 210 or more. when the water temp gets hot, the oil temp goes up. or vice-versa

 

I'm running a four row C/B rad in my 69 502 with 5 blade clutch fan....in traffic with ambient air temps of 100 F,coolant temps never exceed 210 f....180 stat,btw...

 

You have a couple of problems to address:
1 like posted above the fans should never melt any wires or blow a fuse. If it does you have undersized wires for the load, period.
2 make sure they are pulling instead of pushing, simple polarity reversal.
3 stick with the 180* T-stat, the t-stat sets the minimum operating temp, not the max.
4 check the current draw on the fans, if they are drawing more than the spec for the fan says, its bad, get it replaced.
5 where is the temp sensot for the fans and what temp is it set at?

 

Verify your temperature guage readings using an alternate accurate thermometer.
A simple method to check sender unit, is similar to what I suggested for the thermostat..... place the sender in a container with a thermometer and some boiling water and verify the gauge readings coincide as the temp drops.

Of particular interest is the gauge accuracy at close to boiling point ~212*F and the accuracy at the thermostat temp of 180*F.
The boiling point of your coolant will be higher than 212*F in a sealed pressurised system, so don't be concerned if your actual coolant temp gets to 200*F. It's when it goes over 220*F you may have issues. But make sure your temp gauge is reading accurately.

I was stuck in a 1 hour traffic jam on Sunday on our freeway.
It was a warm day. I had never seen my gauge go over 190 previously, and that was only after some very spirited driving. It usually sits at about 170~175. But in that traffic crawl it did creep up just over 200 after 45 minutes of continual stops, lengthy periods of idling motionless and uphill starts. But as soon as I cleared off the freeway, it was back to 175. I have the stock fan with an alloy dewitts radiator. I have the full radiator shroud, but I haven't sealed the gaps around the shroud yet. Will do that now that I've seen I have an airflow issue at idling

couple of other questions....
Do you have an expansion tank or a coolant recovery system installed?
Are you losing coolant over a period of time?

 

WOT and non-WOT are two different creatures. You don't need much advance to run well at rich, high load WOT conditions. Conversely, you do need a boatload more advance to run well (not overheat) during light load, near stochiometric conditions. Unless I'm misunderstanding your info above, it still sounds like you are running a retarded curve here.

 

It is difficult to understand why your components aren't working...i have a very strong 383,no shrouding at all,aluminium rad(with oil cooler and trans cooler stacked in front of it) and a 14" puller electric fan..i have no temp issues at all...what you have should work fine....are you really sure the fan blades are facing the right way and the fan is rotating the correct way.....i know i stuffed it up the first time by having the fans rotate the wrong way(reversed polarity)...also there is no possible cooling issue that will make fan wires melt(short of being stuck to the rad)there is clearly something electrical wrong that must be fixed.....john

 

im using everything that came with the fan as far wires, relays, ect...
i am using a 100 amp alternator. the time that it melted the wires was when i was on a long trip and the fans had to of been running for hours. but they do get hot just tooling around. im at a loss. with everything in place and everything new, i should be able to handle a timing issue or other small problem. i dont know. but i will use all this good advice to contemplate my problem

 

The wires getting hot is a resistance problem. Either the wires are too small of a gauge for the draw of the fans, or the power or ground connections are poor.

Where is the fan circuit getting it's 12V power from, and where is it grounded. Both need to be satisfactory.

 

i had this problem with my 79 vette. i put a new motor in the car new aluminum radiator.dual elec fans.new t-stat. new seals still ran hot.. check your timimg and make sure your carb is running on full manifold vacuum. not ported on the carb..i put my vacuum advance on full manifold vacuum now my vette runs at 180 not the 210 it was

 

Back to DB's original point, check the wiring. Rumor has it harness fires aren't very amusing.

 

Maybe I missed it but what eng are you running your profile is not very informative.
It sounds like you have a new engine lets start out there
also what thermostate are you running

need all the info to try to help you. with out it hell you might have a ford ????"?

 

I don't want to seem like i am dissing you,but if the components are new they should work!!!! but the fan blades can physically go either of 2 ways to cater for push or pull installation and the electric fan motor can rotate either way for the same reason.....it sounds like you are getting enough airflow at speed to cool but not enough airflow at idle...suspect the fan isn't working properly....as to the electrical installation;it has a relay and fuse right???? if it does,there is something horribly wrong if wire are melting.....john

 

rebc3, I'm running a 454 LS5 in Tucson, AZ. I have a 4 row copper/brass radiator. I'm running stock water pump, and a late 90's Lincoln Mark VIII 2 speed electric fan. I wired the fan with heavy duty Bosch type relays, one to key on position. The other is split between A/C on and Temp sensor in drivers side head. I"m running a 195* thermostat. Now I said at the start, I live in Tucson, AZ. I have yet to get to 200* on my 454, hiway, heavy traffic, or just tooling around. If you lower the opening temp of the t-stat, it won't stay closed long enough to allow the radiator to cool the coolant enough before it opens back up and it starts all over again. Before you know it, in about, oh say 20-30 mins., you have a close to overheating engine. Go to a 195* t-stat, check DurangoBoys ideas, and see what you have. Good luck

 

Seems to me that you may have resistance somewhere too or even a bad motor.

So let me see if I understand....Base timing at 16*( which means nothing unless all you want to do is idle !!!!)
And NO mech or vac advance!!!!!
I am too tired to address this at this time but you will need to advance the timing by some method as the RPM's increase. I know almost all will back me up on this!!!

 

Just set your total timing a 34-36 degrees at 3000 rpm and be done with it its not the timing.Come on take off the fans throw them in the garbage put your stock fan on or a flexlite fan,try it see if its the same or makes a big diff.I still say put a single electric fan in front of radiator a pusher-one that pushes air through the radiator and make sure its wired that way-forget the relays control boxes and such for now run 2 wires ground and power to it with a simple fuse inbetween to a switch that you control.when operating temp gets to 170-180 turn it on you should be able then to put car in park get out on a hot day and let it run out of gas and not get hot...........................

 

Get a bigger electric fan...

 

I strongly disagree! If he has no mech or vac advance he is running retarded at any rpm above idle and that Will cause a prob with eng. temp!!!
Mark

 

I beleive his problem is at idle-at least thats what i thought.He says temp goes down when accelerating.If the thing had no mech aor vacumm adcance he would probably be complaining about very poor performance while under acceleration.Dont want to argue ive said what i think he needs to do.Im done with this one.I told him to set total timing at 34-36 degrees-you should be able to see if advance is working while watching pointer,i just dont think its timing.JMO