Alum. Heads

Ok, so while in the process of window shopping for parts, I come across a sett of eddy e-street heads, 2.02 int. 185 cc runners 64cc chamber.. I get to thinkin, nice! Dad comes at me with, your motor runs 200f on a cold day, 220-240 normal day (70+) those heads wouldn't last long before they warpped.. The motor is a 350, bored .030 over, stock crank specs, so, my q for you all today is, how hot can a set of alum. Heads run at on a normal day to day, 2 hour max at a time, run before they warp and a grand goes down the drain?  

Hi there,
What about the combustion chamber thermal temp.
I have owned motors that with addition of lots
of Ethynol of Glycol have run a consistant 256*
all day and night without using a cup of water.
 Water temp alone will not kill a motor..Only the
the shortage of it...  
skyeking

Well, i'm not wanting to warp the heads if I get them, thats mainly wat im worried about..  

perhaps some theory of why heads warp


the head gaskets have to be evenly compressed across the entire surface for them to seal properly..


the coolant passages are carefully designed  to evenly cool the head.. even though the exhaust ports are generally much hotter than the other parts..

when pressurized to 13 or 16 pounds pressure, and a 50/50 to 70/30 blend of coolant to water is maintained.. there should NOT be any hot spots that boil the coolant...

but... there is additional in block and head coolant pressure by the flow created by the water pump and the restriction created by the mostly closed thermostat and the small size of the bypass circuit..  

at cruising speeds...  the water pump is building additional pressure inside the block and heads... this raises the boiling point of the coolant even farther..   is also the reason the coolant will flow the long way around through the heater core..


this is why a properly selected thermostat is needed ..  even nascar racers use a restriction instead of no thermostat.. but they are operating their engines above 6,000 rpm..  they do have a problem with the oval tubes in the race radiators sometimes experiencing extreme pressures and attempting to become round..  closing the gap where the air flows between the tubes..

with todays fuel injection system... the fuel systems are programmed to operate with usually a 192F thermostat..  so a normal operating temp of 195F to 240F is expected.   i have seen a lot more aluminum headed motors with 180F thermostats..   why is the proper temp needed..   if the temp is below what is expected.. the fuel injection system keeps the air fuel ratio rich to attempt to warm the engine  to operating temps.. this reduces fuel economy and melts the cats...


without a thermostat.. the engine takes forever to warm up...  the heater core does not get enough flow to warm the interior of the car.. there is no additional pressure created by the pump in the block and heads. so the hot spots can create boiling points where steam bubbles are created and that forces coolant away from that area.. a downwards spiral toward melt down...   under some operating conditions..  the engine will eventually overheat without a thermostat..  as the coolant circulates faster and faster through the radiator.. much to fast for the fan or ram air through the radiator to remove the heat from the water..  


let me now get into head warping..

metals expand when heated...   do to the variable temps in the head.. the exhaust ports are hotter.. the chambers are also very hot..  the head can expand at different rates...  when an engine overheats.. the area under the exhaust ports can expand and crush the head gasket... it can only crush it so far before it cannot expand any farther.. this causes the expanded area to distort.. when this area returns to normal temp.. it is deformed , bent backwards away from the gasket.. this reduces the clamping force that seals the gasket between the parts..    this is what you are worried about i am taking it..



i personally like to take precautions when installing aluminum heads..  i use a product called hylomar.. i spread it on both sides of the head gasket then let it hang to evaporate some of the solvents for 20 to 30 minutes before setting it on the engine block and installing the head..    since i have started doing this back in 1992.. i have not had to redo a head gasket do to failure... i hate doing a job twice... hylomar is a synthetic material that never ever dries.  won't washout.  is good for over 500F... is cheep insurance from having to do the job twice or breaking down..

permatex sells it.. #85249    oh.. don't ask for it as head gasket sealer.. the staff is taught to install head gaskets dry..  they don't have to do them a second time..

proper torque wrench calibration also needs to be verified.. usually with a 15MM 12 point socket to test it against a beam type torque wrench..  since most people have some variation of a click type wrench..   always store click type torque wrenches at 0 or less..

carefully running a tap into the head bolt holes to clean the bottom of threads of corrosion.. as most chevy engines have the end of the head bolts exposed to the coolant in the block...   if you change the head gaskets.. and have the heads surfaced.. the bolts might thread in a little farther.  hit that corrosion.. come up to the turning torque without it actually being the torque from the clamping force..


these thoughts are what i live by...  

Id be much more concerned about the cooling system than I am about heads at this point.  No need to be that hot.

If that is truly the water temp Im surprised you havent cracked an iron head yet.

Is the temp sensor in the head or in the manifold?  If its in the head, this explains things a little.

If its an iron head....keep it at 190 degrees.  If its aluminum....shoot for 200ish steady.

To answer your question.....total myth about heat warping and taking out aluminum heads.  Not that it "cant" happen......but it was always an assumption that it would happen and not any real proof.

You probably are lucky to find a new vehicle with an iron head.  Most all of them are aluminum and water temps are kept in the 220 range for emissions and mileage purposes.  These things go hundreds of thousands of miles and arent warping heads left and right.  Id be willing to bet the quality of aluminum isnt as good as you can get with an aftermarket head either(in most cases).

Id still wanna see 200 degrees at best for a performance engine.

Back to your cooling issues.  What radiator?  Whats initial timing set to?  Is vacuum advanced hooked up and is it hooked to full manifold vacuum or ported?

What fan, and do you use a shroud?  Something is very wrong with the cooling system if a 355 chevy is running in the 220 to 240 degree range.

Lastly.....keep the cam fairly mild with the E street heads.  No roller cam.  The studs commonly break in those heads.  Common enough that edelbrock sells them as
flat tappet only" anymore.

For aluminum on a budget Id consider the dart SHP or brodix IK series of heads.  Also look into a jegs brand aluminum head.  Its a profiler casting which is a very good head  

I'm not getting the heads yet, but the temp gauge is in the head.. On the exhaust side . She normally pulls that temp all day long.. No issues out of her about out yet..  

I'm also running headers, could that have something to do with it too?  

Oleskool,,, have you ever checked the calibration of the temp guages?   with a laser thermometer, you can shoot different areas on the engine and see whats really goin on.      I have checked the guages with it and seen as much as 10* variation in the factory ones.

If you install a 180 deg stat the engine should cruise down the road about 180+  cause the stat wont open till the mentioned temp. The factory installed the sending units in the head and that is the normal location for them, the intake does not make heat the heads is where its coming from so that is the best place to keep an eye on it.  

I run all my sending units in the heads and never had any trouble with that or unusual readings.

I have worked on Many engines,,,,,, with proper maintained cooling systems and fans, fan clutch, etc.  NEVER seen unusual operating temps.

You have a common 350 and this should not be an issue.

NO I have headers on everything in the yard from 305 to 502 big blocks, headers actually keep the engine cooler cause they retain less heat.  

Aluminum heads can easily run 200- 220 deg and will never give any trouble with a properly maintained cooling system, I dont think the big auto companies even make a cast iron head anymore???  

Aluminum does not make more power,,,,, it saves weight, and dissipates heat quicker minimizing hot spots and allows the use of higher compression on a given octane simply due to that.  

Chevelle has it right, fix the cooling situation FIRST. then start looking for performance upgrades. Is your engine stock? Have you done anything at all to it?  

Hi Ole school:

How fresh is your engine rebuild. If you just rebuilt your engine I would put some miles on it. The reason being a new engine is usually on the tight side with clearances... new engines built to factory specs will make a new engine run a little hotter then normal...Think about it tighter rings,tighter pistons,even bearings....As they break in they run better,and cooler...Don't use any temp thermostat lower then 180 degrees F...and don't run without one..

If your temperature pick-up beit an electric,,electronic or mechanical is in the left cylinder head as most small block chevys are....Try installing it in the intake manifold possibly before the thermostat housing.....Compare the two temps.. and take the mean...An engine does not over-heat unless it boils the coolant out of the radiator...it's that simple. ...You know water boils at approx 212 degrees F.....New coolants can go up to 280 degrees F..or above before they boil.... That is if it is under the correct pressure.... If you have a sealed cooling system with the correct pressure cap.....and the coolant is not boiling out your system is working.....

With that said if you are running in temps of 250 degrees F in your cylinder head and 230 degrees F in your intake manifold the mean would be 240 Degrees F.... That for me is too hot for aluminum cylinder heads..... I would want to find the cause of the high temp.... You may never get it to run at 210 Degrees ***

Quick story: I built a little warmed up SBC for my son. He installed it,and lives in another state. He called me and said the temperature was at 220 degees F...He had the temp pick-up in the left cylinder head. I asked him to do what I suggested you try. Temperature was 200 Degrees F.... So the mean was 210 degrees F..Perfect.....I had him take a temperature probe and move the radiator hose enough to get the wire under the hose....The temp was 210 degrees F...Perfect. I had him do the same to the lower hose.. the temperature was 180 degrees with a 180 thermostat installed in it...There was nothing wrong with the cooling system....Its that way still...Good Luck....
Thanks
Bob  

Hi again OLE SCHOOL:

You may want to richen the carb. Running headers will make the engine run a little hotter....Sorry about that.
Thanks
Bob  

running the temp sender in the head will always show a hotter reading than it does in the manifold by the waterneck.  the reading is usually more eratic also cause the temp swings in the head more than it does by the waterneck.

So because you are measuring it from the head...your temp figures might not be as bad as initially thought because if yuo were measuring from the intake....it should be cooler and might end up more in line with where it needs to be

Personally Id read from the intake manifold.  More consistancy and easier to reference if your at the right temp.

harder to make an honest call when referencing cylinder head water temp  

Excellent post.  
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Code to find out, it was running a 195° stat, so I changed it to a 180, and instantly the reno was reading alot cooler.. It has stayed( temp gauge on head) in between 180° and 220°  from the driver's seat  

Dave632

Is there a place where we can sign up and get them thrown out?