Aluminum vs. Iron Block...

torqueIT · Feb 20, 2004

The V-6 has the iron, the V-8 has the aluminum block.

What pros or cons can you think of dealing with each?

Rootus · Feb 20, 2004

All else being equal, iron weighs more, and is slightly stronger. Aluminum is also a little louder.

Dave

shatner saves · Feb 20, 2004

Aluminum also has better heat rejection. Note that top fuel dragsters have aluminum block and heads.

USN_MustangGT · Feb 20, 2004

One of the only negatives that I can think of for aluminum is that it can warp easier if you neglect your car . . . like overheating it repeatedly or letting the coolant freeze. ummm, threads in aluminum will become stripped much easier.

Aluminum is pretty much better in every way, better heat dissapation as was stated before, weighs something like 55% of iron, doesnt rust.

Ray III · Feb 21, 2004

Aluminum blocks are weaker overall, whether you're looking at peak horsepower capability, tightening bolts, cleaning off mating surfaces, etc. Its softness and significantly different thermal expansion rates from other parts are issues as well; must be sleeved with cast iron cylinder liners and that among various parts like engine bearings are going to expand less with heat than aluminum... which is asking for trouble to mix such dissimilar metals like that if you ask me.

On the plus side, they dissipate heat much more rapidly, are easier to machine, and lighter weight which can result in a significant advantage in a normally nose-heavy car.

For performance purposes aluminum heads and blocks are superior to cast iron, but you will never see aluminum blocks on an engine that has to survive many years of abuse.

awalbert88 · Feb 21, 2004

Aluminum blocks are lighter, dissipate heat better, and are fairly durable. However, iron blocks are pretty much bullet-proof, which is why the 03 Cobra motor got an iron block. I'm not really sure why the V6 has an iron block rather than aluminum, though. Possibly to keep enough weight over the front end to avoid upsetting the handling balance?

shatner saves · Feb 21, 2004

it's cheep. I thought I read somwhere that the v6 was all aluminum.

(?)

351CJ · Feb 22, 2004

shatner saves said:
it's cheep. I thought I read somwhere that the v6 was all aluminum.

(?)

The 4L SOHC V6 uses an iron block.

The 2.5L 3.0L and upcoming 3.5L Duratec engines use aluminum blocks.

80deathtrap · Feb 23, 2004

The added heat dissipation of the Aluminum is in general a bad thing. The lost heat is heat that wasn't used to make power. Idealy there would be no heat loss from the engine and no parts would fail if heat built up. In that respect Iron is better than Aluminum because it retains more heat in the cylinder and is less affected by the heat. Only if you go air cooled do you want the added heat transfer of Aluminum.

351CJ · Feb 23, 2004

yea, but the cylinder liners are iron.

shatner saves · Feb 23, 2004

80deathtrap said:
The added heat dissipation of the Aluminum is in general a bad thing. The lost heat is heat that wasn't used to make power. Idealy there would be no heat loss from the engine and no parts would fail if heat built up. In that respect Iron is better than Aluminum because it retains more heat in the cylinder and is less affected by the heat. Only if you go air cooled do you want the added heat transfer of Aluminum.

That isn't "lost heat that wasn't used to make power". That's waste heat that wouldn't be used to make power anyway.

Maybe I could pick up a few horsepower by throwing my radiator away.

rhumbline · Feb 24, 2004

shatner saves said:
That isn't "lost heat that wasn't used to make power". That's waste heat that wouldn't be used to make power anyway.

Maybe I could pick up a few horsepower by throwing my radiator away.

And the greater thermal transfer ability of AL allows greater design flexibility for more power, i.e., cooler cylinder heads allowing higher compression ratios for example. Theoretically, the hotter a motor runs, at least in the combustion chamber, the more thermodynamically efficient it would be (more power and/or economy). That is one reason why jet and rocket motors can create so much power from such relatively small motors, they combust at significantly higher temperatures than internal combustion motors can tolerate reliably and economically with today's materials.

The reality is that, as in all engineering endeavors, there is a multitude of variables and compromises that must be considered. Overall, the lighter weight and greater thermal transfer capabilities of AL represent a better engineering solution than FE, which is why so many engines use it.

Vlad · Feb 25, 2004

Ray III said:
Aluminum blocks are weaker overall, whether you're looking at peak horsepower capability, tightening bolts, cleaning off mating surfaces, etc. Its softness and significantly different thermal expansion rates from other parts are issues as well; must be sleeved with cast iron cylinder liners and that among various parts like engine bearings are going to expand less with heat than aluminum... which is asking for trouble to mix such dissimilar metals like that if you ask me.

On the plus side, they dissipate heat much more rapidly, are easier to machine, and lighter weight which can result in a significant advantage in a normally nose-heavy car.

For performance purposes aluminum heads and blocks are superior to cast iron, but you will never see aluminum blocks on an engine that has to survive many years of abuse.

know of any other manu's who are doing this? doesnt mercedes use an aluminium block on their v8? I thought bmw did too but I have also heard that some of those m3's and m5's will go bang for no good reason.

also, assuming that this engine could be prone to block problems, anybody got any tips on what would be the best way to take care of an engine like this?

65conv50 · Feb 25, 2004

Vlad said:
also, assuming that this engine could be prone to block problems, anybody got any tips on what would be the best way to take care of an engine like this?

Talk to the Corvette and late Firebird and Camaro owners. The LS-1 is aluminum, I understand. I've heard of no real problems with it. My LT-1 is iron, so go '98 or later.

Ray III · Feb 25, 2004

Don't overheat it... You'll probably be fine with an aluminum engine that stays cool like it was intended to, but the fact that iron motors easily survive severe overheating, breakage of internal parts, etc. is why I'll stick with one in my car.

As to that part about the aluminum blocks not keeping the combustion chamber at proper temperature, all you would have to do is raise the coolant temperature some more to slow down the rate of heat transfer. Since the manufaturers seem to run aluminum motors at the same temperature, there must not be any such problem.

95GTvert[bv12] · Feb 25, 2004

you can repair aluminum blocks if they crack and you have to toss and iron block if it cracks

ComfortablyNumb · Feb 25, 2004

ok, say someone gave you a lot of money for your weekend racer blown 5.0, would get an iron or aluminum block ?

65conv50 · Feb 25, 2004

ComfortablyNumb said:
ok, say someone gave you a lot of money for your weekend racer blown 5.0, would get an iron or aluminum block ?

If I were gonna race it? Iron.

Rootus · Feb 25, 2004

95GTvert[bv12] said:
you can repair aluminum blocks if they crack and you have to toss and iron block if it cracks

You can toss a lot of iron blocks for the cost of one aluminum one ...

Sean`03///Zed4 · Feb 26, 2004

Generally speaking advantages of using Iron block is more. Aluminum (rather use of Al as an alloy)is there for bulk savings. Metal to metal pure Al's boiling point is almost 5 times less than Iron, therefore it can only be used as an alloy to form engine blocks.

Iron's strength (rather weight) is 7 times greater than Al. This means that a castiron block is more elastic, noiseless and resistant to wear than aluminum , thus from longevity and stength standpoint over time CI is a winner. They are also quieter as they absorb shocks/vibrations more. Al alloy blocks need special pressure casting, rib formation and when it has a stroke equal to or greater than the bore then usually a CI plate is bolted to the bottom end for added strength. All this brings down the weight savings to about half over CI.

But manus make Al alloy blocks because they can be pressure die casted, the process (assembly line process)is cheaper, the final finish is always more refined and smoother, therefore less friction within the moving parts. But almost all al alloy blocks are CI lined for each cylinder. Usually CI blocks have siamesed walls but al alloy blocks can be casted s.t water jackets are formed between the cylinder walls for better heat dissipitation.

For oversquare high revving engines i would take an Al block. It holds out fine. For a stroked or blown motor CI is better , longevity over time. For a square config. like the 05 4.6l motor Al block should hold out fine because of the cubical design of a V8 block which brings in a natural geometrical stifness.

Aluminum vs. Iron Block...

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