Temps climbing in 318

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valiant1966

valiant1966

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First the specs. I have a 66 Valiant that was /6 but now has a 318 with automatic trans. The engine has a very mild cam and a performer intake with eddy 4 barrel that runs a little on the rich side. Timing is 16 initial and 35 total. I have about 1500 miles on the engine and it has done this since day one.

I use a 195 thermostat that was tested in a pan water with a meat thermometer. I have tried 2 gages. One electric, one mechanical and both give the same reading. The lower hose has a spring in it so it doesn't collapse. I use a 50/50 mix of water and antifreeze.

I use a clutch fan and the radiator was used with my /6 with air conditioning. It was new and is rated for a /6 with air. Also has a shroud from the /6. I have a new Stant 16 lb. radiator cap that has been checked. I know some of the folks don't care for the lever type cap but it was checked and as long as they work properly I see nothing wrong with them.

Now, the problem. It seems that I can cruise all day long around town with no issues(190-195) but when I get out on the highway, the temps start climbing(up to 220-225 so far) and appears to want to continue to climb. It has never gotten any hotter because I always stop at that point not wanting any serious problems. Once it has got that hot, it doesn't really want to come back down when I get back to slower in town speeds but doesn't continue to climb.

I'm thinking the radiator is too small and not carrying enough coolant but I don't want to spend a bunch of money on a new one without having more knowledge about it. What do you all think? Sorry about the long post but you want details and now ya got them. Thanks in advance. Dennis

http://i968.photobucket.com/albums/ae170/obe1kanoby/Cooling2_zpse2b40b0e.jpg

http://i968.photobucket.com/albums/ae170/obe1kanoby/Cooling_zpsc078630c.jpg


http://http://i968.photobucket.com/albums/ae170/obe1kanoby/Cooling2_zpse2b40b0e.jpg
 
sounds like your radiator is to small. Try turning the heat on, fan on high and see if that helps drop the temp. You can also back off the timing 5* and check temp. Gasohol doesn't need a lot of timing.
 
Needs more radiator or that one needs rodding out.
 
I just went through the same thing /6 radiator and pretty much the same combo as you.Champion 3 row 22" cured it.
 
Let me tell you my interesting experience. Sometime ago, OldmanMopar had posted that he believes that something (thermal cycling, ??) sometimes causes the fins to crack loose from the tubes. What this would do is to still allow great water flow, but reduce heat transfer

My 360, and later, a 318, with the original 273 67 2 core, did EXACTLY as yours. I had junked a /6 73--74 which ALSO had a 2 core in unknown condition, with the later style tanks.

I switched them, and the result was DRAMATIC. By the way, a rad shop told me my original 67 flowed plenty of water, and was clean. He told me it should cool a stock 360 "no problem."

I believe, that at least in my case, loose fins on tubes was the problem.

"Some day" I'll try and set up a test between the two.
 
I think that fan shroud isn't doing you any favors because the air is missing a big part of where the hottest coolant is.

Lets say this is your radiator.
The red represents the hottest coolant area of flow, and the blue is your fan draw area.
In spite of what people think happens in a radiator, reality is more consistant with this drawing. (you can prove it with a temp gun)

See what I mean?

That being said, flow volume is usually the cause of overheating on the hiway.
Has the block been flushed out well. (hot spots can make it overheat)
What is the age of the water pump?
Is there a spring coil in the bottom hose.

Then there is also the possibility that it is the radiator like RRR mentioned.
Was it backflushed before it went on?
How do the tubes inside that you can see look?
 

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Thank you all for the ideas and opinions. I really appreciate them. It looks like most here feel the same as I do...the radiator is too small. I was just hoping that since my build was not radical that maybe I could get by with it. It just didn't seem like it should change it that much but it seems others here have experienced the same thing.

Trailbeast, I will remove the shroud and see what the difference is. Doesn't cost a dime to try that.

Yes , the lower hose has a spring in it as stated in my original post and the radiator is new as I said also. Water pump is new also. I ran it(the radiator) on my slant for about 6 months before dropping the small block in and the slant was clean. Not full of rust and crap. Dennis
 
It's not the shroud or the fan. Neither are relevent at highways speeds.
 
67Dart273 said:
It's not the shroud or the fan. Neither are relevent at highways speeds.
Click to expand...

That's about the bottom line whether it's radiator plugged, fins separated, or too small.
(Unless it is the water pump or screwey thermostat, or a dirty block.) :)

I didn't mean to take the shroud off, but to have one that covers the entire radiator surface.
 
Capacity or flow.

But I would think that a new radiator, /6 AC (heavy duty cooling), should keep up with a mild 318.

Does the spring in the lower hose run the entire length of the hose?
 
1968FormulaS340 said:
Capacity or flow.

But I would think that a new radiator, /6 AC (heavy duty cooling), should keep up with a mild 318.

Does the spring in the lower hose run the entire length of the hose?
Click to expand...

Temp doesn't want to come back down after getting hot and then slowing down again, so probably not the hose is what I was thinking.
 
1968FormulaS340 said:
If the spring is as little as 4" short is can collapse, I have seen it happen. That's why I asked.
Click to expand...

Thanks for that link on the sprang, I meant to tell you. Good stuff. And it's a Ford part. Might make these Mopars a little faster. LOL
 
The spring runs to within 2" of each end of the hose.

I built this 318 for this swap. It was tanked and new parts installed along with the heads just prior to dropping it in.

The /6 is alive and well. I gave it to a friend and he is running it in his 68 Dart. Dennis
 
valiant1966 said:
The spring runs to within 2" of each end of the hose.

I built this 318 for this swap. It was tanked and new parts installed along with the heads just prior to dropping it in.

The /6 is alive and well. I gave it to a friend and he is running it in his 68 Dart. Dennis
Click to expand...

Then I would have to agree with "not enough radiator"
 
Try it on the road without the fan shroud first....just for thoroughness. The way the shroud is setting behind the rad, and with the flat, shallow nature of the shroud, it is blocking a significant amount of the total airflow at road speed. The shroud edges should be completely outside the core area, and it should be deeper and more bowl shaped, not so flat. Even with a large rad, I would not want to use that shroud.

Also, is the rad core support opening such that the rad core is completely open to incoming air, or is it partly blocked? And are there foam or rubber strips around the front of the rad core opening to the core support, to seal the air pressure and force the air through the rad core rather than allowing it to flow around the sides of the rad? I ask because I have run a larger and moderately powerful V8 (300-350 HP) with a 2 row rad core and it was fine.
 
Well, it looks like the consensus is "too small radiator" from what we/I know and the info I have been able to provide.

One more thing. Would it have an effect since the inlet and outlet are on the passenger side of the radiator? I wouldn't think so because all the coolant flows into a common tank on top and distributes itself through the system?

I sent a PM to challengergary and if I need to get another radiator I think I might get one with the intake on the drivers side just to provide better distribution.Dennis
 
The inlet and outlet on the same side is uncommon, for the reasons that you are probably suspecting. The flow across the top of the tank is not as free as you might think. I posted some other suggestions, comments above.
 
Not uncommon on /6. That's how the ones I have seen are and the shroud is the one that came on the slant, I just relocated it since the V8 fan was in another place.

I ran it without the shroud when we first dropped the engine in with the same results I have now. That is why I decided to try the shroud and see if it helped. Thanks for the suggestions. Dennis
 
TrailBeast said:
I think that fan shroud isn't doing you any favors because the air is missing a big part of where the hottest coolant is.
Click to expand...

I would also recommend a different shroud. The one you have is not any good (don't mean to sound harsh, but just to the point). It's not letting the fan do its job. :eye:

The only opening in the back of the shroud should be where the fan goes. The purpose of a shroud is to make a "nozzle" to direct the air to the fan, so it can pull air through the radiator. With the openings that I have circled, you are not letting the fan pull the air through the radiator. The whole back side of the shroud needs to be covered and the only opening is to be around the fan with just enough clearance so the fan doesn't hit the shroud. Your shroud does not let that happen.

Your position of the fan in the shroud looks ok to me. This is called FOOS (and not Chip Foose), it is an acronym for Fan Out Of Shroud. The shroud should cover about 50% of the depth of the fan give or take approx 15% so the fan can draw the air through the radiator. The fan being too far inside or outside the shroud will hurt the ability of the fan to pull the air through the radiator.

The shroud's biggest benefit is when you are not moving or going very fast. I would find a better shroud.


Now in this case, I don't believe that the shroud is causing your overheating problems, but I took a closer look at it when Trailbeast mentioned it. He has a good point that the shroud is not adequate.


Usually overheating problems are when you are not moving fast or at all, you have the opposite problem. At highway speeds you get "ram air" effect through the radiator from the car moving and the fan is not necessary - that's when the clutch fans disengage.

Have you tried to spray the radiator with a hose when it's hot to see if it helps cool it down? When the car is hot/overheating, spray the radiator with a garden hose or car wash hose and see if the temp comes down. That will indicate if your radiator is the bottleneck/weakest link in your cooling system. It sounds like your radiator does not have the capacity to cool your engine (maybe clogged etc).


Keep in mind when looking at new radiators, area before depth. You get more benefit from adding area than you do depth, if you have the space for it. The thicker the fins/rows are, the more resistance to air flow it has. Thicker is not always better to a degree. I wouldn't go more than 3 row. If you have more area to increase the radiator size, then that will give you more cooling capacity without restricting airflow. You would be better going from a 18" radiator to a 22" radiator if you have the room, than adding more rows to a 18" radiator (this is just for example to prove the point and not implying that you have an 18" radiator).


I agree that your problem is due to not enough capacity for the radiator. But also recommend getting you shroud improved also. You want the whole package to be correct.

View attachment Cooling_zpsc078630c B.jpg
 
I would also recommend a different shroud. The one you have is not any good (don't mean to sound harsh, but just to the point). It's not letting the fan do its job.
Click to expand...
No offense taken to anyone here. I came asking for advise and I take it however it comes. I haven't liked that shroud since day one but it was "convenient". After I get with Gary, and hopefully get a new radiator, I'll build a new shroud that fits properly.

I've got this thing tuned to run great if I can solve this one "little" problem. Heck. I had a small block Vega(sorry) before this and didn't these cooling problems with it. That's where I found out that flex fans aren't good for sustained high rpm's. Ha! Thanks all. Dennis.
 
valiant1966 said:
Not uncommon on /6. That's how the ones I have seen are and the shroud is the one that came on the slant, I just relocated it since the V8 fan was in another place.
Click to expand...
Not on the slant 6 sitting in my drive (1962)....original radiator. But, I have not seen all slant 6 radiators! What year(s) do you have? The shroud does not look like a factory piece to me; I thoguht they were all molded plastic....??
 
I'm thinking that back in 66, not so many parts were made of plastic or fiber. I know for certain that the one I have is factory original but it had factory air also so maybe that made a difference. My friends 68 Dart had a /6 with the outlet/inlet same as mine...passenger side. Dennis.
 
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