Cast Iron Engine Blocks & Heads vs Aluminum

[Shel_B]

A few months ago, I overheard a comment that suggested cast iron blocks and heads are stronger than the same components made of aluminum. That comment meant to me that, in certain stressful situations, an engine would give better/longer service were it made of iron. Certain heavy duty truck Diesels, construction equipment, and maybe even some racing engines, would be better if made of cast iron.

Are there any HD Diesel truck engines, construction equipment engines, big boat or ship engines, built of aluminum? Are any dedicated racing engines built of iron? Essentially, if strength and durability were the primary concerns, would iron be a primay choice?

 

[siriusc1024]

Strength to weight ratio and application.

 

[Snagglefoot]

If you look at the Chevy 6.0 used in the 3/4 ton until the 6.6 came out, the block was cast iron and the heads were aluminum. That was probably a good combination for block durability and modern combustion characteristics of the heads.

 

[siriusc1024]

If you look at the Chevy 6.0 used in the 3/4 ton until the 6.6 came out, the block was cast iron and the heads were aluminum. That was probably a good combination for block durability and modern combustion characteristics of the heads.

Yep, and the 6.0's started off with iron heads. The reasons for transition to aluminum should elucidate a few things.

 

[dishdude]

Cast iron also doesn't expand and contract as much as aluminum when it warms up and cools down.

 

[Skippy722]

Can’t speak on durability, but machining cast iron kind of sucks… The “chips” turn into a hard to remove mud in the coolant.

 

[Slick3914]

Cast iron can crack in the main webs, that’s why 410 sprint cars are all aluminum blocks now.

 

[Jetronic]

A few months ago, I overheard a comment that suggested cast iron blocks and heads are stronger than the same components made of aluminum. That comment meant to me that, in certain stressful situations, an engine would give better/longer service were it made of iron. Certain heavy duty truck Diesels, construction equipment, and maybe even some racing engines, would be better if made of cast iron.

Are there any HD Diesel truck engines, construction equipment engines, big boat or ship engines, built of aluminum? Are any dedicated racing engines built of iron? Essentially, if strength and durability were the primary concerns, would iron be a primay choice?

eventually, aluminum blocks and heads will fatigue and crack, while that's not an issue with iron. But I'm not sure we still have roads by the time a well designed aluminium engine suffers from that.

How many engines you know about that don't use aluminum pistons? those are the most stressed parts of an engine and they still last while made from aluminium.

 

[Cujet]

Quality cast iron is really hard to beat when it comes to simplicity and ease of manufacturing. Stable, strong, long wearing. Consider that American car manufacturers made cylinder heads and blocks from cast iron without any additional valve guides or valve seats or cylinder liners. Just machine the castings and use 'em. The higher the iron quality and the better the oil, the longer it lasted. A million miles was possible on diesels and a few hundred thousand was possible on gas engines.

An example of a cast iron cylinder head that is both light weight and long lived:

 

[nascarnation]

Anybody on here old enough to remember when the Powerglide automatic had a cast iron housing?

 

[tnt_motorsports]

Cast iron can crack in the main webs, that’s why 410 sprint cars are all aluminum blocks now.

it's a weight thing, IMO.

 

[tnt_motorsports]

@Shel_B in my mind it is based on some simple rational

Motorsports are not necessarily about durability it is about being durable enough, therefore aluminum is used to gain the weight reductions. When it comes to HD engines it is cast because of durability and longevity.

 

[CheezWhiz]

pretty obvious that cast iron has durability advantages considering the GM iron block 6.0 in the HD trucks even when they made an engine with the same displacement but an aluminum block for the half tons.

use of aluminum for engine blocks is about weight savings for racing or fuel economy, not for durability.

 

[Nessism1]

pretty obvious that cast iron has durability advantages considering the GM iron block 6.0 in the HD trucks even when they made an engine with the same displacement but an aluminum block for the half tons.

use of aluminum for engine blocks is about weight savings for racing or fuel economy, not for durability.

I'm not so sure about that. An aluminum block has a big advantage when it comes to strength to weight ratio. Aluminum blocks open the door for all kinds of fancy, and durable, cylinder coatings and/or different cylinder materials.

Where iron wins is low cost, sound absorption/damping.

 

[CheezWhiz]

I'm not so sure about that. An aluminum block has a big advantage when it comes to strength to weight ratio. Aluminum blocks open the door for all kinds of fancy, and durable, cylinder coatings and/or different cylinder materials.

Where iron wins is low cost, sound absorption/damping.

you think GM cares more about NVH in their HD trucks than their half tons? Look at the thermal expansion coefficients of both materials. Then tell me which one you want to use for an engine block in a 3/4 ton truck that tows 10,000 lbs five days a week with a hungover 18 year old at the wheel for a decade.

 

[k1xv]

Perhaps the most durable auto engines in my memory were the Mercedes OM617 series 5 cylinder diesels, some fitted with turbos. These engines were cast iron blocks and heads, and with proper care, could go a half million miles or more.

https://en.wikipedia.org/wiki/Mercedes-Benz_OM617_engine

 

[BMWTurboDzl]

A few months ago, I overheard a comment that suggested cast iron blocks and heads are stronger than the same components made of aluminum. That comment meant to me that, in certain stressful situations, an engine would give better/longer service were it made of iron. Certain heavy duty truck Diesels, construction equipment, and maybe even some racing engines, would be better if made of cast iron.

Are there any HD Diesel truck engines, construction equipment engines, big boat or ship engines, built of aluminum? Are any dedicated racing engines built of iron? Essentially, if strength and durability were the primary concerns, would iron be a primay choice?

The S54 (early 2000's) used in the BMW M3 was cast iron w/aluminum heads.

 

[Exhaustgases]

Reason for Aluminum on the now made cars, is cheap cheap cheap. Low melting temperatures for casting, can use dies.
Its the fastest metal to machine that is strong "enough" for some applications. Though to equal steel it needs to be about 3 to 4 times thicker and more in some cases, and that negates any weight savings, for close to equal strength.

Sure weight savings in applications were things can be done good enough to get buy, so to say.
Areas that need high bolt torques the iron will way out shine the aluminum, think Northstar and the time sert mess.
Also aluminum parts will flex more than the iron or steel counter parts.

 

[Exhaustgases]

eventually, aluminum blocks and heads will fatigue and crack, while that's not an issue with iron. But I'm not sure we still have roads by the time a well designed aluminium engine suffers from that.

How many engines you know about that don't use aluminum pistons? those are the most stressed parts of an engine and they still last while made from aluminium.

There are actually quite a few that are now, and have been in the past.

 

[Jetronic]

There are actually quite a few that are now, and have been in the past.

I knew this was coming.... do those last longer than engines with aluminum pistons?