Thread: 331 hemi from a new Yorker what temp is safe

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I been running this for about 2000 miles my last 330mile trip I was running hot at 55-75 how hot is safe with this hemi

Around town or 1 hr trips have never gone above 195 but I saw 220 and seemed to run fine

I do have a th350 tranny behind it.

Thanks for any input!!

Welcome to CHR. Running 55-75 cruising you should be at your thermostat control temperature if everything is right - no air bubbles in the system blocking flow, enough radiator volume, good water pump, no air flow restrictions, etc. Where is your sending unit located for your gauge giving you the 220F at cruise? What's the setup in the car? In mine (not a hemi) I found that my temp in the water jacket by the heads (ECU input) ran ten to twenty degrees hotter than my dash indicator measuring at the water neck, so I backed my T-stat down from 195 to 180 and reset my fan controller using ECU temps and it's been fine. 220F is not going to hurt the hemi, but I would be concerned with it being that high at cruise - you don't have much cushion left.

Personally that's a little warmer than I'd like to see it, but it willl probably survive at that temp. On a hot day with the AC on mine normally runs between 190 and 210 (210 is where the clutch fan locks up).

Is your temp guage electric or mechanical, and where is it located? Are you sure it's accurate?

hotter than I like to see but check accuracy of your guage and give us some more details about the install---underdrive pulleys?? what water pump???fan?? radiator and shrouding??? change your type of fuel/gas???? different oil???

Jerry makes a point especially when it comes to pulleys. The pump pulley should be smaller than the crank pulley. That will put an overdrive on the water pump. That will drive the pump alittle faster at low speed, which will push more coolant. Also is the fan shrouded? if not it should be.

There is a temperature gauge quirk that both my HEMIs have. It has to do with running a mechanical gauge and the location that I use to screw the end of the pickup in (the crossover pipe that connects the 2 cylinder heads where the thermostat is located).



At above 2000 RPM or so the gauge will show 5-7 degrees hotter than the engine is actually running. You can actually watch the needle jump if you quickly step on or let off of the gas.

As near as I can figure this is where you have the 2 streams of water colliding and possibly the highest pressure in the system. I think what is happening is when the engine is reved that the pressure is slightly compressing the liquid filled bulb causing the spike in the gauge.

I've mentioned this before............I bought one of those Mr Gasket radiator caps with the thermometer in it and it is super accurate. My dash gauge is 20 degrees too hot, but when I shoot the engine with my infared gun it is exactly the same as the radiator cap reading. So I just ignore my dash gauge these days. I would strongly recommend one of the Mr Gasket caps to anyone who is questioning their operating temp.

Don

I have a cooling system test kit that has caps, pressure pump and you can put a test guage into the coolant of the rad thru the cap--highly accurate and i recommend getting one for anyone fooling with this stuff.

Mike--That cross ove r on stock hemi arrangement actually disapates a lot (well some) heat and altho handy for the sensor will be somewhat inconsistent at various vehicle(airflow) speeds and eng rpm for coolant flow---

Wow so much help thanks all!!! Ok I'm not sure how to start but I will start with the temp is mechanical on the intake right beside the head. I have confirmed with a infared that I can trust the gauge up too 195-200 I never tested it at higher temps. I have not therm just a restricter plate at 1", hold on it gets much more interesting! I have the stock pump and pulleys. A new rad very big in the back of the rat with 32 feet of 2" pipe 26copper and 6' rubber. Rad in back of the pickup 142 wheelbase it's long 4'doors. I have a helper pump on the return with the fan on the top of the rad with a shroud good flow rad is on a 30% angle a little lower that the top of the intake. But I have a pressure tank that is higher and has hold 3 gal. As the hole system hold 9 gal. It all seems to work great except on those long hot fast trips. The nice this is i can stop shut it down leave fan and helper pump and cool to 140 in 5-10 min. I will add a pic as soon as I figure it out soon again I can't thx you all enough for all the advice!!

Wow! 32 feet of radiator hose!! You've got to have a circulation problem, and my bet is you've got air trapped in the system that is restricting flow. With nine gallons of coolant you shouldn't be seeing 220F cruising temps unless you're holding back the hot coolant from getting to the radiator. My first thought was that you may need to take the stock water pump out of the loop and just use a right sized electric pump? How did you select the flow capacity for the helper pump? I'm thinking two pumps in a closed loop may be your problem - one may be cavitating - but I'm not sure of that yet

As far as posting pictures, the easiest way I've found is to link to a photo server like photo bucket.

Here are a couple of more thoughts for what it's worth.

The first thing I'd try would be to replace the restrictor with a thermostat. When I first started driving my 354 I was running a 160 thermostat and it would run well above that temp and get very warm (over 220) on hot days pulling hills with the AC on. I switched to a 190 thermostat, and now it normally runs 190-200, and under load with the AC up 210 (where the fan clutch locks).

If the thermostat doesn't cure it the next area I would look at are the stock pulleys. As I recall, the stock waterpump pulley is huge and actually larger than the crank pulley (basically you are underdriving the waterpump). It may be a case of the pump not being able to move enough coolant at higher RPM.

I also wonder about the possibility of the radiator and fan being in an area that becomes a low pressure area at speed, limiting the amount of air that is available for the fan to actually move.

Jerry you're right about the temp sender location (and I remember the discussion about locations from a while back). Anyway the location choices I had were the back of the intake manifold (on either side) or the crossover. I picked the crossover because I feel that lets me see temperature from both sides of the engine rather than just one.

One of the things I personally found really interesting is using an IR temp gun at various locations on the engine to see the differences in certain areas (one thing that really surprised me was how much the temp drops from the thermostat housing to the radiator inlet).

Mike's right - you had no problems on short runs, running around 190F or less, but on a longer road trip temps went up. That does not fit with an air block, but it does fit with air flow through the radiator being restricted by air over the cab/bed area, or coolant flow problems like the pulley size. I'd check out Mike's suggestions first, and I would definitely try a thermostat.

I thought about maybe standing the rad up in the back and replace the tailgate? What do you think? I am going to put the thermostat back in 190? The helper pump I have is for a race car 1" in and out. And maybe disable original pump or not if the rad works???

Smaller size tubing to keep the flow velocity higher and put a Lincoln electric fan on the radiator

splice in a section of clear tubing/hose to see if you have air in the coolant flow(foam) or solid water flow.

you definitely have built in a lot of places for air/steam pockets to form and WILL continue to have problems until you get all the basics about liquid/air flow corrected

I might suggest that if you want to continue with the rear rad that for longer trips you mount a pump driven off the driveline(trans or rear end) to augment the flow