I'm baffled so here goes (and I've searched so much I need a beer).... 1966 F-100 Flareside with 1972 FE 390, mild cam, headers, Sniper EFI, power steering, front power disc brakes, Vintage Air A/C and Tremec TKX 5 speed. Antifreeze flow is good with 180 degree thermostat. Tried numerous configurations for overheating and here is what I currently have: Champion Radiator (EC433 2 row, my mistake as I meant to get a CC 433 3 row) with 7 blade clutch fan with no shroud. I had factory original radiator (fixed and cleaned out by radiator shop) with a recommended OEM plastic shroud (D3TZ-8146-C) and previous clutch fan mentioned with overheating still. Thus went to the Champion radiator. With this current set-up I still have overheating issues. Warm temps highway speed 70 MPH around 190 temp. Idling in town (stop lights/drivethru, etc) will shoot up to 220. Hot days even on interstate will shoot up to 210 and try A/C it's gone up to 230. I'm looking at 2 - 12" electric fans with aluminum shround (Champion) with the current 2 row. I like the polished aluminum look so I do not want to go with the factory black plastic shroud mentioned above).

My question is should I go with the Champion electric fans/shroud or move up to the 3 or 4 row radiator? I'm thinking I'll still need the shroud combo as mentioned, but, will going to the 3 or 4 row really help? Also, thermostat is 180, should I go up to a 195?

Open to all suggestions/recommendations. And thanks for your time!

 

Al, If you had the original in it, reamed and rodded, and it was overheating, it's not the radiator. Where is your ignition timing set? Is it running too lean?Both of these can cause overheating. Is the heater core hooked up? Is the fan clutch weak? The way I test them (not recommended) is to make sure I can spin it with the engine off then hold it while someone starts the truck and see how hard it pulls. Should feel like a 3-4# bass is pulling on it, not a fingerling trout. If you can spin it counter to rotation while it's running, replace it.

 

If the heads were off the engine, are you certain the head gaskets were installed correctly?

 

Is it boiling over? Are you sure about the accuracy of the temps?

 

As mentioned, there are several items to check before spending more money.

Was the engine recently rebuilt and if so how many miles since the rebuild? Depending on how good of a job is done, it may take 500 or so miles for a rebuilt engine to run normal temperature. They shouldn't run hot after a rebuild but they sometimes do.

 

JMO but I would check and make sure the thermostat isn't sticking. Had a similar issue with my 66 352 V8 and the t-stat was sticking, looking in the radiator there was flow but it was restricted and caused overheating problems.

 

Thanks Dan. Waiting for a new timing light to show up, a friend can't my old one (haha). I believe the new EFI is running lean and I will be taking it to a mechanic that knows his stuff on these things (I can't get it to idle right, might go back to the carb). Heater core is hooked up, however, I haven't ran the heat for quite a while and when I first had it running with the old set-up, it had a bubble lock. I'll give that a try first. Clutch fan is operating as it should. It'll take me a while, just had a hip replaced so I got that going for me this winter.

 

Thanks all, some very good points. I'll try to summarize...
CD: No issue with the head gaskets, heads haven't been off
KO: not boiling over and I'm confident on the accuracy.
65: around 5,000 miles on the rebuild
WTX: Don't think it's the thermostat, but, I was thinking of moving up to a 195. As long as I'm playing with it, I'll boil it to make sure it's opening.

Going thru drive-ins or sitting at stop lights, I just rev the rpms back and forth to keep the temp down when engine temp hits 210. It really got me worried and overthinking on the way to Louisville, KY this past August. Outside temp was around 95 and I was staying around 70mph on the interstate when I tried the AC and engine temp went from 210 to 230. After I shut off the AC went back to 210 and stayed. Return trip was around 90 @ 70mph and stayed around the 210 temp, didn't use the AC.

 

If you are having problems getting your EFI to idle right read thru this thread. Throttle plate fit - Ford Truck Enthusiasts Forums (ford-trucks.com)
Sounds a little like the AC condenser is restricting the air flow. Maybe if you post in the 61-66 forum some folks with AC that don't have overheating will chime in on the parts they used.

 

Good point CD. I have the Vintage Air A/C system, I'll give that a shot also.

 

Hi,

I had a similar issue with my truck and it turned out to be the clutch on the front of the fan. To trouble shoot, I removed the fan assembly and put the back of it in my vise. I then spun the fan blades cold to feel the resistance. I then put a heat gun onto the thermostatic spring on the front of the clutch to heat it up. Then I spun the blades. It should have had much more resistance to spinning but mine stayed the same as when cold.

Also, a shroud will make all the difference in the world. With the shroud installed you will want to shim the fan so that the blades are 1/2 way into the shroud. When not running a shroud you want the fan clutch as close to the radiator core as possible.