Running Hot?

[Hellcat]

Hey Guys, I wanted to get some opinions on my situation. I have a fresh rebuilt 440-6 that has about 500 miles on it. I originally put a 195 thermostat, radiator was a standard factory 26" 4 core with a fan shroud, viscous fan, and it consistently ran at 205 degrees at idle and low speed. Out on the highway it would run at about 208 and got as hot as 210 at one point. I replaced the thermostat with another 195 and got the same results. Just for experimenting I replaced the thermostat again with a 180, and the engine ran at 190 to 192 degrees. Continuing the experiment, I replaced the radiator and put a 195 thermostat back in and the engine ran around 200 instead of 205. I didn't get it out on the highway yet to see if it would go higher. The engine has always seemed to run just fine and it never acted too hot. It wasn't hard to start and it would shut off with no issues in all of the configurations I listed above.

Engine Details:
440 bored 0.030" (so 446 I believe)
aluminum Stealth heads from 440 source
Comp cams hydraulic roller cam XR274HR-10 1800-5800 RPM range (15" of vacuum at idle)
FBO ignition system, 34 degrees timing with mechanical advance, 48 degrees with vacuum advance also kicked in
Headers with 3" dual exhaust
10.5:1 CR
Cylinder pressures are all around 200 psi

Radiator is now aluminum (26") from US Radiator
thermostat is 195
water pump and neck are aluminum and from 440 source
the gauge set is dakota digital rallye set for the E-Bodies

Here are my theories/questions:
1) Could the aluminum pump and thermostat housing be tricking the thermostat? Do you think it is possible the coolant could be 200 coming out of the block and then drop to 195 over by the thermostat?
2) The gauge could just read hot.
3) Should I even care? If I leave it as is and it runs at 200....maybe I should just let it be?

Let me know what you guys think. Thanks for reading.

 

[DetMatt1]

Get yourself one of these first to verify your gauge readings.
The 5 Best Digital Temperature Guns | Product Reviews and Ratings

 

[Adam]

Do you have a 440 source water pump housing? I do, and I was surprised that inside the casting one of the passages on the right side was only big enough for a finger to squeeze in! I had to get out the porting/polishing tools and open it up quite a bit.

Also, I have never had good results with viscous fans, they slip too much. Put a solid spacer in temporarily and see if that makes a difference.

Lastly, with the warm engine idling, thermostat open, look at the lower radiator hose and rev it up. Make sure the lower radiator hose is not collapsing due to suction. There should be a spring inside, but many replacement hoses do not have them.

 

[Hellcat]

I just ran it tonight. It runs at 200 at low RPM, and it got up to 205 while out on the highway. I got out the digital temp gun and I'm getting 200 on the return hose just above the thermostat which is what the gauge reads at idle. So the temp appears to be real. Another goofy thing it does that I forgot to mention is that the temp will peak very high before the thermostat opens. It got up to 222 before it suddenly dropped...obviously the thermostat finally opened. This is consistent behavior between 4 different thermostats.

My water pump housing is from 440 source, but I don't remember the holes being small or anything.....that was a while back when I put that on so I'll keep that in the back of my mind for now.

I did as you described to test the lower radiator hose and it didn't get sucked in at all.

I will have to try your experiment with the fan next. That temp spike before the thermostat opens has me baffled. Seems like the thermostat would be the root cause there, but four in a row acting that way?

 

[tonysrt]

That temp. peak is normal as long as it drops back down when thermostat is open. My 2010 srt Challenger and 05 Ram with 5.7 does the same thing. Are you using the high performance thermostat from Mr. Gasket. They are brass and seem to work best. They don't have that peak and then drop down. I also drill 1/8" hole on the base of thermostat to keep water circulating all the time.

 

[Steve340]

Disconnect the vacuum advance 48 degrees with those heads is way to much.
34 total should be enough.
Is the heater connected? Those connections allow the cooling system to bleed out air.
This could be causing your erratic thermostat opening, a 195 thermostat should be fully open at 195.

 

[Hellcat]

The heater is connected and I left the heater control on hot just to make sure the coolant was flowing through the heater core. I didn't think to touch the hoses just to make sure they are hot with coolant flow. I will do that next time around. My thermostat this time is a Summit brand. Not sure who makes those for them. I will try and do one thing at a time to see if it helps anything. I'll let you know how the next run goes. Thanks for the help so far.

 

[quapman]

Dump the 440 Source pump housing. There have been numerous complaints about poor flow around the internet for a few years.

 

[Hellcat]

Thanks quapman, I think I might just go back with the original cast iron housing....I think I'm gonna dump the water pump I got from 440 source as well.

 

[moparleo]

Pressure test your radiator cap. Too much advance. Fan only makes a difference at speeds under 40 mph. Go with a thermostatically controlled electric cooling fan. The whole point of the proper coolant mix and a radiator cap that will hold pressure, usually around 16 lbs. on modern cooling systems is to raise the boiling point temp. It is normal for the coolant to be in the 200 degree range . This helps to lower emissions.

 

[Adam]

Not to be insulting, but could you be installing the thermostat upside down?

 

[Hellcat]

Ha, I'm not insulted...I would ask the same question, but I do have the thermostat in correctly. I think you and quapman are correct about the 440 source pump housing. I did a quick google search and found plenty of conversations about the housing have small holes and even restricted flow paths inside the housing. Their issues sound very similar to what my 440 is experiencing. My plan is to put my original cast iron pump housing back on and also replace the 440 source pump. It might be a couple weeks before I get that done, but I will let you know how it goes.