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Horsepower advantage of Steel Heads Versus Aluminum.

Discussion in 'The Hokey Ass Message Board' started by 38FLATTIE, Dec 15, 2010.

  1. stude_trucks
    Joined: Sep 13, 2007
    Posts: 4,755

    stude_trucks
    Member

    No, once you add something to iron, it becomes and alloy, and in the case of motors is typically better known as steel. You said it yourself, they don't pour 100% iron. They use an alloy of iron and of the type that is called steel.

    Cast iron is like an old stove or frying pan, not very strong and even then is probably not truly 100% pure iron.

    http://en.wikipedia.org/wiki/List_of_alloys#Alloys_of_iron
    http://en.wikipedia.org/wiki/Alloy_steel
     
  2. oj
    Joined: Jul 27, 2008
    Posts: 6,454

    oj
    Member

    One thing i know for sure, aluminum in heads needs mass. Esp with a blower, double esp if you have to have water in the cooling jacket. Our heads on the Top Sportsman are huge and they stay sealed up no problem and i spray 600hp nitrous, lots of pressure, the heads on my sbc comp motor are as big as available and they'll leak at the drop of a hat. The difference is mass. And huge head studs, i'd try for 1/2 if you can. Most big motors now use 5/8" studs.
    Since you are making your own, weight isn't an issue i'd go with steel, thick steel at that and who cares if it takes a while to get to temp - you are going dry sump anyway and you'll have the oil up to temp before the motor is ever fired.
     
  3. I was somewhat involved with a nostagia T/F team several years ago. They did run iron heads on aluminum blocks, but this was because of the rules at the time. All blocks and heads were supposed to be factory castings, but so many blocks were blown up there was a shortage. No one was casting the '92m blocks in iron, so aluminum blocks were allowed out of necessity. I believe now the nostalgia teams are allowed (and run) aluminum heads as well.
     
  4. slimpick
    Joined: Aug 4, 2008
    Posts: 97

    slimpick
    Member

    RacerRick's got it - port and chamber design far outweigh choice of material.

    I did look up the thermal conductivity of A356 vs. ductile iron.
    A356=150 W/m degrees K
    D4512=40 W/m degrees K
    (That's watts per meter times degrees Kelvin)
    Obviously the aluminum can move a lot more heat away from the cylinders. A lot of guys like the 90's LT1 engines for this reason. They can turn the advance way up and not get detonation due to the excellent thermal conductivity of the aluminum and the design of the water jacket.
     
  5. BAD ROD
    Joined: Dec 16, 2004
    Posts: 1,532

    BAD ROD
    Member

    Makes sense! Thanks!

    1994 Impala SS "BAD ROD"
     
  6. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    Agreed.... So long as raising the compression doesn't mess up the combustion chamber, and the engine can tolerate it, there are several benefits to having higher compression.

    You can say that aluminum heads make less power. You could also say that aluminum heads can normally tolerate more compression, and require more compression to achieve the same power as iron.



    The terms iron and steel describe the state the material is in. The microstructure of iron may be one or more of several types, but they are all iron. Iron alloyed with nickel, manganese, aluminum, beryllium, etc. is an alloy, but it is still iron. Steel alloyed with molybdenum, tungsten, manganese, nickel, etc. is still steel. Adding something to iron doesn't make it steel. Turning iron to steel is more complicated than that. That some like to call it steel becauise it sounds cooler, or because they don't know the difference, doesn't make it so. The toughest/strongest iron alloys are slightly stronger than the weakest steel.

    I happen to know something about old stoves and cookware. From the 1800s until at least the teens those items were occasionally made of something unusual, but were normally pure iron(grey/pig iron). Sometimes aluminum was add to remove impurities, but seldom anything else. Grey Iron is relatively weak and brittle, but car parts have been made with it.
     
  7. GOSFAST
    Joined: Jul 4, 2006
    Posts: 254

    GOSFAST
    Member

    In ALL apples-to-apples tests here iron heads have always made more power than aluminum's. Thats the way it is!

    We've done extensive builds over the years with all these components!

    This is how it pretty much works:iron heads/iron blocks make the most, substitute aluminum heads, make less.

    In the popular racing field, iron "aftermarket" blocks usually see some add'l 30/40 HP, where aluminum blocks see 30/40 less.

    It all boils down to "absortion" and "heat-transfer" through the cylinder walls/heads! With the aluminum heads, the heat (when the charge is fired) is absorbed by the head material, with iron heads the heat is "reflected" back to the piston, hence, add'l power!

    Thanks, Gary in N.Y.

    P.S. We've done tests where we would remove all components from one standard SBC casting and installed them in a "race" block, the HP went up nominally 40! Upon sonic-testing the walls in many "race" BB's, most are .350" thick after the machining operation.
     
  8. I would like to know where this is "well known and well documented fact". Could you point me to some sort of technical papers that document this? I would like to learn more about your statement. Thanks
     
  9. tjet
    Joined: Mar 16, 2009
    Posts: 1,335

    tjet
    Member
    1. Early Hemi Tech

    There is also another plus from aluminum heads - since you can bump up the compression over the iron heads, 1 full point, you can run a bigger cam.

    Also, it's harder to read the plugs if the piston tops are thermal coated
     
  10. Why would coating the pistons make reading the plugs harder?
     
  11. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    I have seen the subject addressed in an engineering text on internal combustion thermodynamics. I don't remember the name of the book, in fact I lack the math knowledge to understand most of what was in that book. Real world..... I have worked for several shops that did pro and semi-pro level racing. I was an engine builder myself for a number of years. I worked in and spent even more time in what was at the time one of the top engine shops in the country. I have been around lots of performance engine programs. I know of direct apples to apples dyno comparisons between iron and aluminum heads. I worked for an OEM for several years. For 15+ years I had a business where I worked with a wide variety of auto/truck manufacturers. I learned a lot from the many sharp people I was fortunate to have as customers.

    Think about this, the Cadillac Northstar had/has a feature where the engine can be driven with no coolant! The computer lowers the engine's output and randomly fires different cylinders. The fact the engine was aluminum made that feature possible. Iron would not have disipated heat quickly enough. That same situation is why iron heads make more power than aluminum heads. Heat is power. Aluminum allows more heat to escape from the combustion process than iron.

    oj,
    You said your race engine only runs for a short time so it shouldn't make any difference. In the few seconds a drag race engine runs at full throttle the coolant can go from warm to overheating. That's a lot of heat, and most of it is generated by the combustion process. Whether it's 6 seconds or an hour, heat traveling from the combustion chamber to the coolant is energy that could/should be doing work.
     
  12. zman
    Joined: Apr 2, 2001
    Posts: 16,730

    zman
    Member
    from Garner, NC

    iron wins, there have been more than a few articles in the major hot rod mags over the years testing it. Aluminum is much easier to work with though.
     
  13. stude_trucks
    Joined: Sep 13, 2007
    Posts: 4,755

    stude_trucks
    Member

    Iron is an element and a metal one at that. It is the element "Fe". It is either pure iron or it isn't. If it is pure, it is pure iron, simple as that. If it isn't it is an alloy, technically when done intentionally or just impure iron when not. Yes, the iron doesn't change into something else, it just gets mixed with whatever and the resulting molecular interactions and structure is altered. Either just by close association (alloy) or by molecular change as in rust = iron oxide (iron + oxygen, molecule). This is what changes the properties and makes it stronger (or weaker if is such the case). Unless they are pouring 100% pure iron for engine parts, then they are using alloys and I would guess that almost all of them are some version of what is referred to a steel alloy. Steel has mostly iron in it and is just a mix of iron and some other distinct materials.

    So, again, I seriously doubt they are pouring 100% iron blocks and heads. That is 1800's technology. There is no such thing as better iron than other iron. It is either 100% iron or it isn't and it's a fundamental element and is what it is unless you want to start talking about isotope versions and nuclear differences. I don't think Detroit ever got into the nuclear level of iron. At least not before 1964 anyway.

    I am not sure why you are pressing this point anyway. But if you are, you should at least do it correctly. I'm not trying to bust on you. I actually think you know what your talking about in general and in principal. But, on this one detail I'm not seeing it.
     
  14. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    1. You have to burn or work the carbon out of iron to make it steel. Adding alloy won't do it...........................2. We are talking about a flathead here people. Stop saying it's easier to port one head than the other. No ports................................3. Remember, compression ratio is just a number that is easy to get with math. Compression pressure is a more difficult number to get and needs direct observation. But it's the one that counts. You may have an engine with 12.5 Cr that has less compression pressure than another with 9.5 Cr. Learn the difference and it's effect on your motor.................................4. We are not talking about coating pistons here. We are talking about coating combustion chambers. So far i am the only one I have seen here that has had experience with both doing the coating and running it at Bonneville. I am going with my experience over someone else's conjecture.
     
  15. Fe26
    Joined: Dec 25, 2006
    Posts: 543

    Fe26
    Member

    The terms iron and steel describe the state the material is in. The microstructure of iron may be one or more of several types, but they are all iron. Iron alloyed with nickel, manganese, aluminum, beryllium, etc. is an alloy, but it is still iron. Steel alloyed with molybdenum, tungsten, manganese, nickel, etc. is still steel. Adding something to iron doesn't make it steel. Turning iron to steel is more complicated than that. That some like to call it steel becauise it sounds cooler, or because they don't know the difference, doesn't make it so. The toughest/strongest iron alloys are slightly stronger than the weakest steel.

    I happen to know something about old stoves and cookware. From the 1800s until at least the teens those items were occasionally made of something unusual, but were normally pure iron(grey/pig iron). Sometimes aluminum was add to remove impurities, but seldom anything else. Grey Iron is relatively weak and brittle, but car parts have been made with it.[/QUOTE]

    X2, a good explaination.

    Another interesting factor that has been introduced, is the heads will be made of steel. Some very interesting characteristics have been noted in the differences between aluminium and cast iron in this debate. Now it appears there will need to be some opinions and or facts expressed between steel and cast iron. Or are the two materials regarded to be so similar to each each other as to not warrant comparison in this manner.

    Perhaps the only difference will be the relative merits in the machining process of one over the other.

    I also wonder what would be the merit/s of using bronze instead of steel/
    iron/aluminium.
     
  16. oj
    Joined: Jul 27, 2008
    Posts: 6,454

    oj
    Member

    oj,
    You said your race engine only runs for a short time so it shouldn't make any difference. In the few seconds a drag race engine runs at full throttle the coolant can go from warm to overheating. That's a lot of heat, and most of it is generated by the combustion process. Whether it's 6 seconds or an hour, heat traveling from the combustion chamber to the coolant is energy that could/should be doing work.[/QUOTE]

    Smokey Yunichk spent a lot of time experimenting with heat. I know a lot of advance design facilities mess with composits and etc, the newest generation of coatings for pistons, intake and exhaust runners have made improvements in dealing with heat. But, in racing it is all about raising the level of destruction. Our engine will destroy itself at 1575 degrees (at the finish line), i tune it to cross it at 1500 degrees. If you coat the pistons so that it would make the same power and run at 1400 degrees then i'd be foolish if i didn't raise the power level and bring it back to 1500 degrees. We like to finish first. The head material makes little difference in racing, mass in the right place does,
     
  17. I have to say that I am very curious as the why, if Iron heads are so superior, then why aren't any serious race cars using them? If they are better, why don't Top Fuel cars use them? Weight certainly isn't the problem there. How about Sprint cars, NASCAR, Formula 1, etc.
    Are we talking only theoretical differences in power that don't make it worthwhile? Seriously, why wouldn't those who go for ultimate horsepower be using the "better" material?
    Not agreeing or disagreeing, looking for a real answer .....
     
  18. fab32
    Joined: May 14, 2002
    Posts: 13,985

    fab32
    Member Emeritus

    X2????

    Frank
     
  19. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    The reason I brought this up is because it grates on me every time I hear a drag race commentator or TV mechanic refer to common iron(alloy:)) blocks as steel. It is incorrect and people are being misinformed.

    In the context of this conversation alloying is adding other items to a base metal. Calling the product of that that concoction alloy is incorrect. Alloyed steelis not called "alloy", it is alloy steel. Copper - copper alloy; aluminum - aluminum alloy; gold - gold alloy, see the pattern? Iron alloy is a valid term, but we don't seem to be meshing on that. Considering that iron and iron alloy have significantly different structure, properties, and production methods, there is no basis for thinking of iron alloy as steel. Ordinary steel is made of 100% iron. By your definition steel should be called iron?

    Pure iron can exist in various states. Some of those definitely are "better" for some uses than others.

    I said car parts have been made of grey iron. While I doubt there is any grey irion parts on current generation cars, it's use wasn't as long ago as the 1800s. There was definitely grey iron parts on '50s cars, and probably later.

    I can live with being wrong. If you chose to dismiss what I have posted I can live with that too. However, telling me to get it right what you are missing a few pieces of the puzzle yourself is a bit self-righteous on your part.
     
  20. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,349

    38FLATTIE
    Member
    from Colorado


    Oj, I can't swear it makes any difference one way or the other. It SEEMS to me, that if I have less heat loss, I'll have more power. Sure would like to see some hard data.
    And thanks for the oil pump- If this build hadn't got totally out of hand, it was the perfect hotrod pump!



    I'm really not leaning either way. We have to make the heads anyway, so I sinply want every edge I can get. If they make the same power, we'll use aluminum. If one material has the potential to make even 1hp more, we'll go that route, and address any associated issues with it.

    We'll be running gas, with probably 12-14 lbs boost. I don't think sealing will be a problem. Jimmy Stevens told me he used solid copper gaskets, at 15lbs, and felt he could have had more boost and not leaked.



    Either way, these will be big, thick, heavy heads.We will also be ussing larger than stock heads, with extra studs added in.
    And you're right about the oil- the dry sump has an oil heater in it. For that matter, the coolant will be heated too.


    Wow, good info. You will be kind enough to supply us with the test results, right?


    Again, we really don't need to bump up the compression, as the huffer will take care of that.As for the cam, you can only run so big, then it's a waste. We're running a monster anyway, so again, a non-factor.

    I don't get the statement "it's harder to read the plugs if the piston tops are thermal coated". Can you explain? I fail to see where it factors in.


    I've thought of this too! That's why I ask, but I really wonder if it isn't maybe the Ford-Chevy thing all over again!
     
  21. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    Weight...... And as was pointed out, aluminum allows more compression which not only helps compensate for the additional heat loss, but has other benefits. However, with a straight, all things equal, no additional compression comparison comparison, iron wins.
     
  22. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,349

    38FLATTIE
    Member
    from Colorado

    Hmm, all because I said steel heads versus aluminum? I guess as lond as everyone knows the intent of the statement, I won't get too shook if i'm a technically wrong with my terminology.;)
     
  23. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    I guess I can let it slide...... but look at all the crap you stirred up.:D:rolleyes:
     
  24. hotrodstude
    Joined: Jul 30, 2010
    Posts: 70

    hotrodstude
    Member

    somethings work better than others i've never relie on dyno results or computer programs.what i do belive in is seat of the pants results,what i can feal.i have not tried them yet but they have a new alum head for the y-block ford,they are a copy of the 57-59 272-312 head.on the test mule the alum heads produced 56 more hp then the heads used on the test mule.i'm going to try them next spring on an 272/305 yblock. right out of the box. but my take on this is if you fell good about it use it.my biggest problem with alum heads and iron blocks has been sealing the two.on some of the 60's engines iron heads are getting hard to find so its easier to find alum heads than iron,the yblock ford is one of those engines.
     
  25. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,349

    38FLATTIE
    Member
    from Colorado

    That's funny!:D

    When you building a street car, or even most race cars, there are usually multiple chances to run/test the car. This is a once a year event. Even if it wasn't, I strongly believe in proven results, testing, and dyno's. I mean, c'mon- this isn't grandma's Caddy!

    You say you don't believe in dyno or computer results, then quote results from the test mule. I'm willing to bet thast the 56hp did not happen simply because they switched to aluminum heads. I'm guessing these aluminum heads had better passages, porting, bigger valves, etc.
     
  26. stude_trucks
    Joined: Sep 13, 2007
    Posts: 4,755

    stude_trucks
    Member

    Iron is iron and steel is an alloy of iron.

    See here: http://en.wikipedia.org/wiki/Steel

    Steel is not 100% iron. It is ALMOST all iron with just a little bit of carbon for typical, basic steel. Again, I'm pretty darn sure the kind of motors we like to use around here are steel blocks, not just 100% iron. So, calling them steel blocks is 100% correct (unless they are aluminum or magnesium of course). Calling them iron blocks is only 98% correct.
     
  27. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,420

    GMC BUBBA
    Member Emeritus

    Not really , apples to oranges........electronic igntion vs mag another debate.
    Want some killer easy to obtain spark horse power use a mag !:eek::D
     
  28. brucer
    Joined: Jun 5, 2008
    Posts: 332

    brucer
    Member
    from western ky

    if everything is equal on both engines except the head material i would think they'll run the same... the engine with aluminum heads will be lighter by about 50lbs probably..

    where the advantage is, the aluminum cools quicker allowing higher compression without detonation... look at the compression ratios on alot of the newer ford, chevy and dodges.. my 94 camaro runs 10.4:1 compression stock heads and pistons, they'll safely run 11.5:1 on pump gas.. alot of them that mod the lt1 will mill the heads and use a .026 thick head gasket using the stock heads.. alot of this might also be due to the fuel injection and tuning also helping..
     
  29. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,349

    38FLATTIE
    Member
    from Colorado

    So seriously- You think I should run the mag, or not? It's what's planned.
     
  30. BulldawgMusclecars
    Joined: Jul 15, 2010
    Posts: 508

    BulldawgMusclecars
    Member

    The aluminum helps, but don't discount the reverse cooling on the LT1. What works on those doesn't necessarily apply to everything else. In fact, its the only thing I really like about them anymore (after years of messing with LT1s). Not to get off topic, but the later LS motors and conventional small blocks won't tolerate as much compression as an LT1, even with aluminum heads. On a regular street driven (pump gas), aluminum headed SBC I'd shave at least a point of compression over what I would run on a modified LT1, depending on the cam specs.
     

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