some of you guys asked some really good questions, although if you go back through my first two posts on this topic so far you'll see that I already posted the answer.

Interesting thought regarding pulley sizes... it's the stock pulleys, they don't look any different than any other set of Chrysler small block pulleys that I have... and I have literally dozens of engines and twice as many parts in boxes (I have my own little Mopar junkyard with about 50 vehicles along with whole engines and tons of random parts stashed away). Interesting thought though, even though they look ordinary I believe I will take a measurement to verify the diameter. Why not, I've done everything else.

See, it bothers me that this is going on. I've driven Chrysler v8's hundreds and hundreds of thousands of miles with a 3 speed automatic and factory cooling systems. Before I got my diesel, I towed cars through over a dozen states at full highway speed with my 440/727 truck. When we moved from St Louis to NC I drove a 67 NYer with a 440/727 back and forth three times at full highway speed. Just a couple of stories, point is they weren't stymied by today's fuel or less than perfect conditions or anything else. A gol-durned stock 318 with every blooming part on it replaced and every blooming tuning setting quadruple checked shouldn't even come close to having this problem. An 85 318 should continue to purr away after a direct nuclear strike. What the heck is going on here.

I think the new or rebuilt water pumps are the problem the impellers are cheaper and the tolerances start to stack up. Let us know what you find, this problem gets asked often. Maybe a hi volume water pump will help.

One other member had a similar problem. The water jackets were gunked up. Pulling the freeze plugs, cleaning with various tools and a hose got the gunk out well enough to fix it. May be that's what you are left with?

Put me down for airflow. Is there a whinch or big pushbar on the front? Did the PO leave a chunk of cardboard between the condensor and rad?

Wrong fan pitch? IE a reverse rotation fan blade stuck on the water pump? FWIW I ran my RR without a fan for a short time when I had a long freeway commute to work, it stayed cool on the road but would warm up in traffic.

I din't recall if you changed the water pump but I have seen pumps with the impeller rusted off. Loose impeller is a possibility but I would think that would make noise.

How neglected was the cooling system when you got the truck? Rusty mud or somwthing resembling water?

Well , all the things I would have recommended are already done by you or advised by the competent people we have here. So I think it's time to look somewhere else for the heat. I would disconnect the tranny lines from the rad and put a stand alone tranny cooler on there. At least by doing that you have 100% eliminated any chance of it being something other than the engine itself.
BTW what gears you got in that ram. I suspect it's somewhere around 3:55 , Just wondering if the engine is winding a little higher and the water pumps are cavitating the coolant and it's not circulating .

Had the same problem on my 62 Plymouth. Changed the radiator cap and problem went away.

just put -another- new water pump on it yesterday, that's what prompted me to post this.

Rad cap has been changed twice.

here's a pic for the guy wondering about a winch up front:



it's an A/C delete truck with nothing in front of the radiator.

The fan is working great, holds a piece of paper against the rad just fine. And if you reach towards the carb or something while it is running you can feel the air rushing over the area from the fan.

The idea about disconnecting the trans cooling lines is a good one.... I had thought of that a year ago and forgot about it. I was thinking the same thing, eliminate the possibility of the trans fluid heating up the coolant in the exchanger. I'll try that too, thanks for the reminder.

I guess some of you are on to something with cleaning the inside of the block. I have been discounting that since the coolant stays so clean but if there is a LOT of gunk really impacted in there I suppose it is possible that it just stays put. Gonna suck removing the headers and the motor mounts to get to all the freeze plugs so I can get a pressure washer in there... running out of ideas I guess.

What about the question about timing, what is the initial, total without vacuum, and total with vacuum advance?

I would check the radiator temp while its running hot. If it were a water flow problem, the radiator would be significantly cooler than the motor.If it is an airflow problem, the radiator will also be hot.Unless the water flow problem is in the radiator.......
Is there a way you can rig up a thermometer on a bung? maybe the drain?
BTW heckuva nice lookin truck!

After all of the ramchargers from that period I had, only thing left I could suggest, I believe you should have covered by now, is the common issue of the factory worm clamps on aux trans cooler, which is sandwiched between rad and a/c condensor, seeped oil over time and the dirt and dust would collect on cooler core and rad core, slowing down efficiency big time. You could easily spot that issue after removing that big plastic seal thing.

I had the same problem, turned out the fan was not spinning fast enough at highway speeds. Was fine at idle or low speed all day..

Someone mentioned the exhaust & whether or not the truck has the catalytic converter still on or not? Make sure the exhaust is flowing freely - clogged or really restrictive will make the engine temp go way up if it's enough. It would make sense on the highway that higher prolonged RPM would need more exhaust flow.

Also, I used to have a '78 Dodge Super Coupe that always ran hot. Pulled the radiator & had it boiled & pressure tested & it was fine, reinstalled & same hot running condition. Changed coolant & flushed the system & still ran hot. One day, we decided to pull the engine & clean it up, repaint everything (car was for sale & we were bored), & replace all the freeze plugs while the engine was out. When we popped the first freeze plug out, that was our clue. Basically, MUD came out. We pulled them all & really hosed out the passages & a LOT of sediment came out! Installed new freeze plugs, painted everything, put it all back together & it never ran hot again. The crap inside the coolant passages was the culprit. Good luck.

I had a 69 Dart slant six that would do the same thing. I actually used it to tow my Harley down from Illiniose to Daytona Beach for the 50th Bike Week and had to stop every 100 miles or so to let it cool down, it got worse of course because I was towing a single axle trailer. I tried everything on the way down, then I got mad and got ready to throw the radiator cap across the highway! I took a good look at it and the brass seal was cracked it three places! I walked across the street to an auto parts store, bought a new cap, and never had another issue. Basically there was not enough pressure in the system to keep the coolant flowing.

If it hasn't physically boiled over, I am going to call out the gauge. I have had 2 mid 80's dodges do this that had bad engine to chassis grounds. Half gauge at idle, but when I put load on the engine, the gauges would climb, but I wondered why they never boiled over..Replaced the sensor, same deal, put a set of booster cables between the block, the chassis, and the brake master cylinder and the battery neg, gauge never went over half. Replaced the main ground cable, cleaned all the rest of the factory ground points, fixed.

I think the first place I would start, at this point, would be by popping out one of the rear most freeze plugs and seeing how much gunk is in the block. That might solve the whole issue.

I've seen blocks so full of gunk I pulled a freeze plug and it was packed full of sediment, there wasn't even any sign of coolant having been there for a long time. That one even flushed clear before the freeze plug removal!

If that isn't the problem, you need to look for something strange. It well may be a combination of little things adding up. You have swapped a lot of parts. Now its time to shift or relocate some of those parts and see what happens.

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I had the same problem, turned out the fan was not spinning fast enough at highway speeds. Was fine at idle or low speed all day..

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I've experienced this one before as well. A simple test is to pull the fan off and hit the interstate and see if it gets hot.

Is your temp gauge mechanical or electric? I've seen electrical gauges miss read when the charging system is in a high rate of charge. They work fine at lower rpm, but as the voltage increases with rpm, things go array. Like stated earlier, if its really overheating, there should be signs of it doing so, more then a gauge reading.

While your looking at your pulleys, check to be sure the groves are not worn. I've seen recently (these parts are all getting pretty old now) where the sides of the pulleys were worn off and the belts were actually running on the bottom of the pulley instead of on the sides like they were designed to run, The result was slipping belts as the engine rpm increased. At lower speeds everything was great.
The sides of the pulleys need to be "V" shaped, the ones causing an issue were more "U" shaped. Gene

a few thoughts i have is

what kind of water pump did you use?
some hi volume pumps will push the water way too fast thru
the radiator,not giving the water enough time in it to be able to cool down.
a cheap waterpump won't help your cause alot either.
is the radiator cap brand new?
a bad cap can effect the flow also with a loss of pressure.
do you have a shroud?
it helps to create a vortex behind the radiator
that inturn helps air flow alot..