uneven cylinder head temp

[NAM VET]

in the 6 K miles since I acquired my '52 M 37, the coolant temp gage, once the engine is fully warmed up, will go to 210, and stay there. About 2K miles ago, in my rebuild of my truck, I had the engine rebuilt, doing most of it my self, with the help of Charles Talberts shop, who re did my rings and valves, among other things. My motor was tanked clean, and I soaked the radiator in flush for weeks, and when rinsing it out, it was clean. My truck had been driven frequently for 20+ years by the the previous owner. I pulled out the water distribution tube, and it was good, in fact, if I had not had a new one on my bench, I would have reused it. I slightly flared the water pump end to fit the hole in the block. I put in a new 180 thermostat, and my engine is properly timed, runs great, but I still have about 210 on my water temp gage. When I use an infra-red digital gun on my trucks powertrain, the water pump neck and front of the cylinder head is fine at 170 degrees, but as I check towards the rear of the head, at about the insertion of the water temp gage, it reads about 200 or maybe slightly more. Never had any "overheating" symptoms, ie, steam or leaks, oil temps are fine at about 170 or so or less on a hot day. My head has been milled a number of times for rebuild. I run some RedLine water wetter in my 50-50 coolant.

So the rear of my cylinder head does indeed run hot. Anybody have a similar situation, or a suggestion for me. I could put in a 160 thermostat, but I suspect the differential would still be there.

I a running in a local parade on the 4th, have a great week guys.


NV., aka Hal Copple

[rickf]

Just curious, Are you running enough RPM for the water pump to circulate the coolant enough? Maybe run it around the block in third at a little higher than your normal rpm and check it again. If that brings it down then the water pump is probably not moving enough water for whatever reason. You could actually do it just sitting still, run the hand throttle up to about 1500-1700 RPM and test the temps as it is running. Also check to see that the fan belt is not slipping.

[NAM VET]

Ok, will see if that makes a difference. But at my usual cruise, which is about 40 mph, standard tires and gearing, it will get up to the same temp. Hal

[NAM VET]

"...upon further review, with my motor hot, but not running, and thus the needle isn't vibrating back and forth thru maybe 10 degrees, my engine sender is at 200 degrees, not 210. I have the four belt alternator, so not slipping on the fan pulley, and besides, my coolant temp at the outlet of the water pump is is good, about 170 or so. My intake/exhaust manifold was flat surfaced for a leak free attachment to the block. When I pull my plugs and look down on the piston tops, they all look similar, with an even carbon coating, and the plugs also look the same, and also fine. I am running ...43 Autolite military plugs, new too. Hal

[Cal_Gary]

I'd speculate that all of our 230s run hotter in the back since the coolant distro tube tapers down to a smaller diameter. As long as you know you have good coolant flow I wouldn't be overly concerned. I also wonder if you have a heater plumbed back there, and if so, does the coolant or back of the head run a little cooler when the heater is on?

Just wondering,
Gary

[NAM VET]

I don't have any sort of heater, or other sort of water in or out at the rear of my motor. It would be interesting for someone to use an infra-red heat gun to see what their head temps are at various places. I can't think of anything defective in my head or rebuild which would cause this. And perhaps you are right, they all do, perhaps with differences if water outlets are at the rear of the motor, such as a heater or engine pre-heater, which I took off when I got my truck, don't need it in UpState SC anyway. I will see if there might be a way to use the now plugged rear head outlet can be used to increase flow to somewhere. All the best....

NV

[ashyers]

Hal,
I may run to Costco with the truck today. If I do I'll bring the IR thermometer. If I go by the Shop this week I'll use the thermal imager I just picked up and take a photo. It's a neat tool and great for diagnostics.

Andy

[RCrombie]

For what it is worth, Datsun/Nissan 6 cylinders run hotter at the rearmost cylinders as well. From what I understand it is a combination of the water traveling from the pump at the front of the engine to the rear, where it picks up heat and loses velocity along the way. So the coolant from the pump ends up being slower, and warmer at the rear of the engine before it actually has a chance to pull heat out of the rear cylinders and valve area. A racing modification was to make an external water distribution tube that was designed to push additional water to the back of the head. Anyway, this is all pertaining to Datsun 6 cylinders. I would imagine after looking at the water distribution tubes that there is a similar situation with these Dodge sixes.

[rickf]

All engines have hot and cool areas, A 40 degree difference is not drastic but it is something to take note of. Those temps are not something that is going to cause any damage. Also, I have found that the IR guns you buy at places like Harbor Freight are fantastic for doing what you are doing, Comparison, They suck at giving a real world figure. That long and very heavy engine is certainly not going to cool evenly within 10 degrees. I am curious to see what Andy comes back with with the imager. I used them when I was working and they are freaky!!

How about a few more of you guys that are running your trucks on the road break out the temp guns and see what you are reading? I am really curious to see if this is normal.

[Kaegi]

I agree that is normal. but I would switch to the 162 Tstat. they are working hard with such low gears. I like to have the water moving around as much as possible. But either tstat overheating is unlikely. the engines have full length water jackets around the cylinders and are cold blooded compared to many other brands. mopar V8s the same way

[rickf]

If you get below 180 the engine will lose power plus it will build up condensation that will not cook out of the oil and you will end up with gunk and milky residue in the engine. Along with the acids that come with water in the oil.

[Kaegi]

If you get below 180 the engine will lose power plus it will build up condensation that will not cook out of the oil and you will end up with gunk and milky residue in the engine. Along with the acids that come with water in the oil.

it will run hotter than 162 when at speed with 3 tons being moved. the 162 was very common in dodge flatheads in trucks and industrial applications. never had a sludge problem running it.

[rickf]

"At speed" being the key words here. How many people here are pushing there old engines that hard? I am not going to get into all of the laws of thermodynamics but basically the hotter the water flowing through the radiator the faster it will shed the heat to the air so even though you are running the engine hotter it will not overheat with the huge radiator and huge fan these vehicles have. A gasoline engine will run its best at around 210 degrees, there is no way I am suggesting to run these at that temp but it is well known that 180 is a substantial improvement in power and efficiency over running it cold.

With all of that said, The vehicles and the engines in them belong to you and your opinions are the only ones that count when it comes to your vehicle. I only give advice based on my years of experience, I do not preach that my way is the only way.

[just me]

I find the 180 works better in my truck. Even in 115 ambient temps the truck doesn't run hotter than 185.

[NAM VET]

Appreciate the above comments and opinions. But I still have my original question. The front of my motor with an infrared gun around the thermostat is right around the 180 temp of the T stat I have installed. My gage is about 210 but not hotter as long as I turn off the motor to avoid any gage needle flutter. When I use an infrared heat gun, my motor is hotter towards the rear two cylinders, about 195 -200 degrees or so. I had my head off twice at two different rebuilder places, as part of my engine out complete hot tank and rebuild, so I doubt there is a sludge obstruction in the head or block And the prior owner (25 years of ownership) drove it regularly, and maintained it well. So if other owners on this forum have 160 or 180 T stats in their trucks, is your cab temp gage reading the same temp at the rear of the head/block? By the way, the oil temp never gets hotter than about 160 or so degrees, again, with the infrared gun. My water pump is new, and my truck has the four V belt pulley system. I recently had an oil analysis when I changed the oil (I run 10-40 RedLine) and there was zero fuel or water in my oil.

John B has a 160 T stat in the mail to me, as I am about four days from driving about 240 or so miles home in near 100 degree temps. I agree hotter oil reduces condensation and perhaps other contaminates and acids in motor oil, but I change my oil frequently, as often as a thousand miles or less.

What I am trying to understand is why every one else says their truck runs all day at whatever temp on the cab gage as their T stat is. And mine doesn't do that.

Have a great day. I am in a parade Thursday, and the organizers have not yet decided if I can put buy 30 cal on the truck. The parade staff wants it, the head is not so sure, .

All the best, have a great Holiday as we celebrate the birthday of this great Country!!!!

NV