Aluminum vs iron heads on a 9:1 daily driver

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travis
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Aluminum vs iron heads on a 9:1 daily driver

Post by travis »

Is there any advantage one way or the other on a mild 302 sbf? 3300 pounds, somewhere in the 3.55-4.10 gear range with an AOD or 4R70W. Around 9.0 compression, small hft cam (either 208/208 on a 111 LSA, or 214/214 on a 108...I have both). Shorty headers, low rise dual plane and a small 4bbl. Just a driver/cruiser.

I was looking for a set of GT40P heads, but wondering if aluminum heads at this level is worth the expense.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by mag2555 »

Assuming equal amounts of air flow I say this.

Heat in a internal combustion engine is energy and iron heads make more heat then Aluminum ones do.

With your 9 to 1 compression you do not need the cooling effect of Aluminum to stay out of detonation.

Long story short I think you will eek out a bit more power with the iron heads as SBF heads are not that heavy to start with anyway in terms of what the difference the car’s weight will be between both type heads.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by dfarr67 »

Alum is a porters friend, if you can find decent iron heads I would go that route. I had some RHS 2.02 vortecs years ago and they were a fine head.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by Momus »

Aluminium everytime, if just for the weight saving and cooling improvement.

Iron heads are obsolete.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by mag2555 »

Maybe you can point me in the direction of where I can find out how many Diesel and industrial motors are made with Aluminum heads?
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by GerryP »

mag2555 wrote: Mon May 16, 2022 6:11 am Maybe you can point me in the direction of where I can find out how many Diesel and industrial motors are made with Aluminum heads?
Pretty common. My Ford 6.7 Power Stroke(PS) diesel uses a CGI block and aluminum heads. The 6.7 has used aluminum heads since inception in 2011, so it is hundreds of thousands of examples. The European diesels also use aluminum heads. I don't know of every example, so I have no doubt there are contemporary diesels using iron heads.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by n2omike »

mag2555 wrote: Sat May 14, 2022 5:05 pm Assuming equal amounts of air flow I say this.

Heat in a internal combustion engine is energy and iron heads make more heat then Aluminum ones do.

With your 9 to 1 compression you do not need the cooling effect of Aluminum to stay out of detonation.

Long story short I think you will eek out a bit more power with the iron heads as SBF heads are not that heavy to start with anyway in terms of what the difference the car’s weight will be between both type heads.
Engine Masters did this very test on one of their newest episodes. All else being equal, ALUMINUM makes more power. They did a test with identical heads. They even flowed both, and even though the iron flowed 'slightly' better by a few CFM, the aluminum made more power.

Cooler engines make more power as the chamber is cooler... so the air/fuel is flowing into a lower pressure area. Aluminum will be cooler, so it will flow better and make more power. Will also be more detonation resistant.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by tuffxf »

Got to agree with Mag on this,
Heat in the chamber is power and torque, some light duty diesels use aluminium but in my job with heavy earthmoving equipment I haven't seen an alloy head, not saying there isn't.
Mind you they are heavy!
But on a 9.1 daily driver if I had a choice, similar design head id
Pick the cast iron every time, who cares about a bit extra weight, the driver can probably lose some anyway.
If for some reason you lose the coolant out of it and get it hot , do a head gasket with the cast iron you'll throw a new head gasket on it and bless it.
With the aluminium you'll be straightening the head , welding up the head where the gasket has failed.
Cheers
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by dfarr67 »

Momus wrote: Sun May 15, 2022 10:51 pm Aluminium everytime, if just for the weight saving and cooling improvement.

Iron heads are obsolete.
That's a very broad statement- and I disagree. I've run RHS iron and AFR alum on a 355, it's NOT a night and day difference- in fact I was disappointed at the difference. EFI application, I'll say a good iron head beats a poor alum head any day.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by dfarr67 »

n2omike wrote: Mon May 16, 2022 8:50 am
mag2555 wrote: Sat May 14, 2022 5:05 pm Assuming equal amounts of air flow I say this.

Heat in a internal combustion engine is energy and iron heads make more heat then Aluminum ones do.

With your 9 to 1 compression you do not need the cooling effect of Aluminum to stay out of detonation.

Long story short I think you will eek out a bit more power with the iron heads as SBF heads are not that heavy to start with anyway in terms of what the difference the car’s weight will be between both type heads.
Engine Masters did this very test on one of their newest episodes. All else being equal, ALUMINUM makes more power. They did a test with identical heads. They even flowed both, and even though the iron flowed 'slightly' better by a few CFM, the aluminum made more power.

Cooler engines make more power as the chamber is cooler... so the air/fuel is flowing into a lower pressure area. Aluminum will be cooler, so it will flow better and make more power. Will also be more detonation resistant.
No such things as an identical iron and alum head.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by n2omike »

dfarr67 wrote: Mon May 16, 2022 10:09 am
n2omike wrote: Mon May 16, 2022 8:50 am
mag2555 wrote: Sat May 14, 2022 5:05 pm Assuming equal amounts of air flow I say this.

Heat in a internal combustion engine is energy and iron heads make more heat then Aluminum ones do.

With your 9 to 1 compression you do not need the cooling effect of Aluminum to stay out of detonation.

Long story short I think you will eek out a bit more power with the iron heads as SBF heads are not that heavy to start with anyway in terms of what the difference the car’s weight will be between both type heads.
Engine Masters did this very test on one of their newest episodes. All else being equal, ALUMINUM makes more power. They did a test with identical heads. They even flowed both, and even though the iron flowed 'slightly' better by a few CFM, the aluminum made more power.

Cooler engines make more power as the chamber is cooler... so the air/fuel is flowing into a lower pressure area. Aluminum will be cooler, so it will flow better and make more power. Will also be more detonation resistant.
No such things as an identical iron and alum head.
If you subscribe to Motortrendondemand.com you can watch the episode yourself.
Identical castings from Dart. Iron head actually flowed a touch more, but the aluminum head flowed more air and made a little more power.
The reason given was because of FLOW. Aluminum chamber was cooler, so it was at a lower pressure than the iron. Air flows from high to low pressure. Their airflow meter showed the aluminum head flowing more air on the running engine... despite the lower flow bench numbers for the aluminum head.

People are set in their ways of thinking, but the dyno test produced actual data. Same engine. Only difference was the cylinder head material.
Detonation resistance is a bonus.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by PRH »

The basic combo outlined in the OP seems like it would be served just fine by some slightly reworked factory heads.

It would come down to cost for me.
Whatever the best bang for the buck is that fits the application.
Somewhat handy with a die grinder.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by mag2555 »

Sorry , but cooler air is dencer then air at a higher temp, this is what moves air around the planet and is why fearce windstorms take place when colder air is pushing hotter air around.
It's a basic principle of nature!
If there did Show a sliver more power from the Aluminum heads then it was due to the length of the Intake runner in the heads being cooler .
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by 54chevkiwi »

Its not worth the expense if its a 9:1 engine designed to just cruise. With those parameters given, any discussion on heat retention and the imaginary power differences between the two on THIS engine or weight savings being beneficial are all moot points. Your favourite cam grinder-er could compensate for all that.

If you own iron heads, use them and cam it for the most torque over the widest range possible.
If you want to spend $2000 more, get aluminum heads, cam them for the most torque over the widest range possible.
If its 30lb/ft more with alloy heads port design who cares. How much power do you need to cruise at 70mph to work for you 20 min commute? How much power do you need to hear it go BRRRRMMM when you put your foot down..
Cheap factory iron heads will do all that.

MY personal opinion would be to go iron and spend the savings from alloy heads on something like atomic efi, fitech, etc and yea, build it to run on piss water for your miles of smiles guilt and problem free cruising.
Last edited by 54chevkiwi on Mon May 16, 2022 12:56 pm, edited 3 times in total.
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Re: Aluminum vs iron heads on a 9:1 daily driver

Post by dfarr67 »

305 heads might even work with small chambers and up rated valves.
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