I have a strange overheating problem that I need your help with, here's what's happening.

Driving in town my temp is normal even on hot days or even if I idle for a while but if I get on the highway my temp will go high just below the H on my stock gauge. This happens intermittently. Today it was running perfectly fine on the freeway however the other day I had to work the engine just a little to go up a 10 mile hill at 55 to 60MPH. It got so hot I was almost at the point where I was going to pull over and let her cool down but I made it to the top and it didn't overheat but it was close. When I started going down the hill I put it in neutral and let her coast. My temp was normal coasting down hill.

I think it has something to do with the engine RPMs.

Here's some quick facts.
- Before I replaced the heads it never had any temperature trouble at all.
- Has the F350 heavy duty radiator that was replaced just before I got it.
- Broken fan shroud. (On my short lists to fix)
- New fan and clutch
- New engine coolant
- New 180 thermostat
- No leaks or loss of coolant
- Having trouble finding the best timing but I have plenty of power on the highway.
- Oil pressure stays at a good consistent level.
- Never overheats, just gets really warm... too warm.
- Factory gauges.
- Edelbrock intake manifold with valley pan gasket.

 

Could be the bottom rad hose is collapsing. You got a coil in it. Easy to check. If you can squeeze it easily when cold then probably no coil or a coil that's too short inside.
Easy to build one if you need to.

 

Do you have that deathly water pump squeak? Whens the last time you flushed the block? Knock out a core plug and see if the blocks all full of scale.

What I'm thinking is a combination of advanced timing and a lean mixture. What do your plugs look like? Are they tan ish brown or more white? And how much advance are you running?

Lastly, its a long shot and I'm not trying to insult you in any way (I've seen a ground strap bolted in between head and the block, a backwards head gasket is not necessarily careless installation) , but are you sure the head gaskets are in the right way? You mentioned this happened since you replaced the heads. Could you possibly have them in backwards? I've seen a block or two that are symmetrical except for one water jacket, and you can really get screwed up.

When it's really hot, check it with one of those laser thermometers. Your factory gauge may be off.

 

First get an aftermarket temp
Gauge. Second X2 on the lower hose collapsing. Definitely check that.

 

X2 on the temp guage, mine was scaring me until I put in a mechanical, never gets past 190 deg, which is what my T stat is. You could do a temporary install just to check your factory guage if you dont want to replace the stock one.

 

Ditto that, the factory "weather" gauge is only an estimate of actual temp range at best.

 

I just checked the lower radiator hose and there is no spring and its very pliable.

Head gasket. I was very careful to make sure I had the correct orientation when I installed the head gaskets so I'm sure I got it right. Now since you mentioned it, now its stuck in my head. Kind of like "Did I leave the garage door open when I left home?"

No water pump squeaks or leaks.

I have the mixture set for a half turn rich after it idles rough which is where the default setting is on the Edelbrock carb.

I know aftermarket gauges are far superior than the factory I just like the clean dash I have (Except my 2-Way radio). I'll have to revisit this again and get an oil pressure gauge too.

 

I built a coil for my hose out of 14 gauge galvinized wire I bought at the hardware store.
Wrapped it around a tube that was about 1.75 inches across mounted in my vise. Bent the sharp ends back over. Made it about the length of the hose. Pulled the hose off and wound it in. Made sure it fit full length.
No overheating after that.

 

X2 get that spring in there I'd bet that will take care of the problem.

 

On a side question. Where's this 10 mi hill. In the area the only real long hill I can think of is Pacheco or altimont pass.

 

i had a lower hose collapse on me only when the truck was ran for a long period of time.
it was fine around town but once i got on the highway at speed if i hit a hill it seems the
hose would shrink due to the suction from the pump. once i replaced the lower hose for
one with a spring it was fine.

 

I'm glad someone asked! It was HWY 17 Westbound going to Santa Cruz.

I will get that hose this week! I'll keep everybody posted on the results.

 

Understood, but keep in mind that you won't really be able to properly diagnose the issue until you have a better way to quantify the problem, which is an aftermarket temperature gauge. Maybe you install a new gauge and it tells you the same thing, but at least then, you know for sure what's going on. At the very least I would test the gauge and the rheostat as a first step to make sure your factory gauge is at least in the ballpark - obviously you don't need to know to within 10 degree accuracy what's going on for this case.

 

Ah didn't think that far south. hwy 17 used to be a real fun road in a muscle car. Now it's too damn busy.
Hope you got your issue figured out with that hose.

 

Get yourself a nice triple gauge set that mounts under the dash, maybe something retro like pictured below that fits the era of the truck, if need be just remove two screws and you're back to a stock factory look...