70 has a problem with the temp creeping up

[Lars]

Running a 2 core 340 rad in my 70, 180 stat, 18" viscous fan, new water pump. Iron headed 360, mild cam (.480ish on both sides, can't remember exactly). Ever since I got it together it has had a temp creep problem. Running down the road at 55 mph (about 2600-3000 rpm, no tach yet), it runs cool, but when I slow it down to about 45-50 mph it starts to heat up, slowly, but consistently. It also does it at idle, but only after I've been moving. If I hammer on it, it will cool down also. At first I thought it was the summer time when I finally got it together (ambi temp was 95-100 deg), but now we are having good temps (70-80 deg) and it still has the problem. It was worse until I advanced the idle timing to 16 degrees (IIRC), but it still is there. I was thinking about buying one of those aluminum radiators. Any ideas?

 

[340mopar]

Sounds like your radiator is right the limit of being too small. The radiator should be large enough that it will maintain temp at 35mph or faster without a fan.

It is better to go wider and taller (adding surface area) than it is to add cores. Of course this only works if you have the space to go larger. If you are already at the size limit then you have to add cores or bigger cores.


Chuck

 

[demon seed]

You didn't mention if you've got a shroud on the rad.

Terry

 

[ted_sweet]

exactly

You didn't mention if you've got a shroud on the rad.

Terry

 

[340srule]

How high does the temp climb too???...

 

[Lars]

Yeah, it has a shroud, forgot to mention that. It'll go to 210 and keep climbing if I let it.

 

[demon seed]

Yeah, it has a shroud, forgot to mention that. It'll go to 210 and keep climbing if I let it.

Next I'd check the thermostat, remove it and but in a pot of water on the stove with a thermometer. If it's 180degF it should start opening around 175 and be fully open at 185 also it should be stamped usually on the bottom of the bulb with a 180. When you said you installed the new water pump is it a high flow pump by chance.

Terry

 

[Lars]

Next I'd check the thermostat, remove it and but in a pot of water on the stove with a thermometer. If it's 180degF it should start opening around 175 and be fully open at 185 also it should be stamped usually on the bottom of the bulb with a 180. When you said you installed the new water pump is it a high flow pump by chance.

Terry

Standard pump. I know the stat functions properly also because I always check them before I install them.

 

[Longgone]

Has the radiator been rodded out, sounds like it`s not taking as much heat out as it should with each successive circulation of water. It may need a cleaning.

 

[demon seed]

Has the radiator been rodded out, sounds like it`s not taking as much heat out as it should with each successive circulation of water. It may need a cleaning.

Yea that was going to be my next suggestion Lars cuss really that 2 core should do the job. It sounds like you've checked most everything else Lars. If everything checks out you may have to go to a 3 core or a high efficiency 2 core

Terry

 

[Lars]

Has the radiator been rodded out, sounds like it`s not taking as much heat out as it should with each successive circulation of water. It may need a cleaning.

It's a brand new radiator. I bought it so I wouldn't have this problem.

 

[demon seed]

It's a brand new radiator. I bought it so I wouldn't have this problem.

Jesus Lars, you're not making this easy.#-o

 

[66dartman]

My 360 runs hot in traffic(210) but before I added som Purple Ice it would go to 220+. I don't know what the stuff is, but it lowered the temp 15* on my engine. Just 2c.

 

[Lars]

Jesus Lars, you're not making this easy.#-o

Pretty good aren't I?

 

[Longgone]

You might try a high volume thermostat like Milodon?

 

[demon seed]

Pretty good aren't I?

Okay Lars this is way out there but I'm running out of ideas, is your fan spinning the right direction to pull the air through the rad. You did mention you've got a thermostatic fan and I'm not even sure that's it's possible to bolt the fan to the viscous housing backwards.

Terry:-s

 

[thanson_mopar]

you mentioned that the water pump is a standard relacment right? try a high flow/volume water pump. Standard might just not be enough to do the job

 

[Lars]

Okay Lars this is way out there but I'm running out of ideas, is your fan spinning the right direction to pull the air through the rad. You did mention you've got a thermostatic fan and I'm not even sure that's it's possible to bolt the fan to the viscous housing backwards.

Terry:-s

Yeah, it's on right, I can get a shop rag to stick to the grill when it is idling.

 

[Lars]

Think I need one? It's only like a 300 horse 360, it's not really that wild at all. What is the normal threshold on those things?

 

[SGBARRACUDA]

I throw my 2 cents in. It sounds like your have a water flow from the block to the radiator problem A radiator is a heat exchanger. The fact that it cools at higher rpm tells me your system is lacking in water flow. I like to place a radiator thermomator in the top with the cap off and see what the temp difference is bettween it and your gauge(a mec. gauge), it should be lower but not alot lower. Next i would have thr radiator flow tested at a radiator shop to make sure the radiator is capable of doing the job. A good radiator shop can tell you this. I assume the pump belt is tight? Next you can go to a A/C type pump as it has two extra impellers, you can speed the pump up by using a smaller pump pulley or larger crank pulley. Next is long shot, but you may have so much sedament in your block that water is not getting to all the surfaces. I run a 360 with an original 69 273 A/C radiator in my Dart and it runs cool all the time. I'm fixing to put A/C back in it so we'll see what happens. Good Luck