Thread: Aluminum 406 cooling problem

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Hello all, having trouble keepin' my huffed aluminum 406 cool. After initial start, the thing will heat up to about 220-230 degrees before the thermostat opens. It'l drop back to 190 and just creep up from there and stay at 230 degrees. Got the timing set at 15 before TDC per the B&M Tech Man. Checked the thermostat buy heating in a pot, opened at 180. Also cheched my gauge the same way, temp indictes correctly. I'm sensing the coolant temp on the passenger side of the intake manifold about 3.5 inches from the thermostat. Suspect the aluminum is pulling so much heat out of the engine so very quickly, that the coolant at the thermostat isn't warm enough to open it. Was thinking about installing a 160 to 170 degree thermostat, but that goes against normal overheating logic. That should drop the opening temp to 200 to 210? One other thing, the other engine I was running with the blower was all cast iron at 352 cubes, I had no cooling problems even in 105 degree ambient temps. That engine would rise to 200 and back to 180. Any input would be great!

OK whats this engine in ?( whoops 31 ford coupe) I'm only asking because as I have said elsewhere with a supercharged engine you need a good cooling system. So if you have a cooling problem it is either an air flow problem or a water flow problem. Be nice if you could send a picture so we could see if you are running fan shrouds, electric fans size of the radiator etc. S

I'm not all that concerned with the over/under 35MPH factor you describe. It does though, run fine on the freeway. Around town I thought it was ok, but she got hot, but not boiling hot. I'm more concerned with the initial start up temp at this time. I'll fix one problem at a time. I'm not running a hood right know, to much pretty stuff (bling, as they say) to oogle over! I talked with a rodder buddy of mine this evening, he suggested not running a thermostsat, instead run a calibrated hole in place of the thermostat. Don't think that's a good idea. He did get me thinking, I'm going to try drilling two 1/8" holes in the themostat flange to pull some coolant towards the thermostat, that may even out the intial temp problem. If that works, I will do some more test at slow speeds, to see if the engine will get to warm for my liking. If so, I will fab up a fan shroud. I've never needed one before, maybe this engine is slightly to pumped not to? A little technical info, 93' Rodeck 350+ Block "O" Ringed W/Copper Head Gaskets, Brodix Track 1 Heads Pocket Ported, Scat Crank & Rods, JE Pistons, Crane 538/558 Hyd Roller Cam, B&M Powercharger 250 Blower @ 10PSI Boost, Cooling is a Walker Cobra Z Series Radiator for big blocks and blown motors, and I'm running a Vintage Air 14" Curved Blade Electric Fan @ 2500CFM.

Electric fan !!!!!! Theres your cooling problem. There is no way no how an electric fan is going to shift the amount of air that an engine driven fan is going to move. An electric fan is mainly used in conjunction with an engine driven fan. Granted, some ricers only use electric fans, but you have areal motor in your rod and you need a real fan. What you want to do is lift the bonnet on an earlier american car and lean over the engine (dont get caught up in it !) and get the throttle linkage and hold it at 2000 rpm, that big windmill shifts a lot of air dont it ?
I have personaly been to a few burnout compititions, and that is one of the hardest compititions on cooling systems around, the car is practically stationary and is putting out decent power, to stay cool that car is relying on its fan to get the job done. Now as an observation practically all the electric fan cars were overheating or poping there radiators, "gee I wonder why ?"
So I would seriously recomend that you put the biggest 7 blade steel fan that you can physically get in there. There has to be at least 4 to 5 inches between your pullys and radiator right ???

Hi blwn31,
That sounds like a pretty impressive motor you have there, sure would be more fun driving than trying to sort out cooling problems. I would listen to techinspector on this one. If you dont have a shroud on the fan I would get one, if you get a nice tight one on there the fan will be more efficient when you are at low speeds or stopped. One of the things that we found in Australia with the LS1 motors was that the Aluminium blocks moved the heat so quickly that engine bay temperatures got quite hot, and the headers needed ceramics to try and keep the temp down. The aluminium motors also seem to come up to temperature faster, this is my observation with 2 LS1's compared to a cast iron 308 (holden) motor.

The best advice I can give you is to check out where your problem is exactly, ie is it cooling down at cruising speed etc, then you will only have to fix the problem once.

Good Luck

4 to 5 inches I wish, try 3/4". It's not called a hot rod for nothing!

See ya! Gotta get in the garage before bed time!

Bleed holes in the thermostat are an excellent thing to do to minimize cold to running temperature coolant temperature. Hope you get that point. You still have the thermostat doing it's job of warming up the engine but not such dramatic thermo swings. I would even suggest 3 holes that are 3/16" diameter.

I drilled two 1/8" holes in the thermostat, now the engine warms up nicely and doesn't go over 180 degrees. Next, I will fix the under 35MPH heating problem, by upgrading to 2 electric fans. A fan shroud is out of the question, no room. Right now I'm running one 14" fan at 2000 CFM, plan on using a 10" @ 1440 CFM and a 12" @ 1770 CFM that should take care of it, 3200CFM, even with the air on...Freeway speed is great at 160 to 180 all day long.

Sounds like you checked all the mechanical concerns by checking the thermostat, gauge,and water pump ?
Now do this :
1. Water is alot better heat transfer agent then anti freeze. Make sure you only use about 30-35 % anti freeze in your cooling system.
2. You can use the 180 or 160 thermostat. I like the 180 better because of less cycling of the water between the radiator and engine. Gives the water more time in the radiator to cool.
Drill one 1/8" hole in the base of the thermostat. Position the hole so that its in the 12 o'clock position. The hole is to relieve air pres. buildup around the thermostat that could prevent it from opening at 180 or 160 degrees. Helps purge the air from the cooling system.
3. Most alum.heads are notorious for building up pockets of air around the # 8 and # 7 vave chambers. If the cooling system has been drained for whatever reason.
Upon refiling the system jack the front of the car up so that gravity will force the water back into the rear of the heads. Be sure and just add enough water so all the tubes in the radiator covered.About a half the tank ought to do it.
4 .With the cap off start the car while its still jacked up and let it idle for about 15 mins. slowly adding water as its needed in the tank. Be careful that the water from the tank doesent belch all over you.
5. Let the car down, fill your radiator full put the cap on ( at least 15 lbs. cap )and go for a nice easy drive for 6-10 miles. The gauge will go up to 230 or so and start to settle down as you drive.
Around the 180-200 range should be o.k. Ive seen alum.headed chevys run all day at 230 and never hurt them at all.
6. Back at the house let it cool down and add water again if needed.
Hope this helps

Thanks for the tips. 230 degrees is still hot, not sure it's a good idea on an all aluminum engine?