Arrhmmm.....with respect the iron heads hold the heat in the combustion chamber better and last time I looked these were thermal engines. I can only guess the F1 guys use alloy because of weight savings and where the heads are located (higher centre of gravity). Possibly the drag queens and speedways guys go the sameway, but more likely it is that there are a larger variety of alloy heads available than iron, simply because they are cheaper to make in small quanitities.

<EDIT> More than likely the F1 heads have ceramic coated combustion chambers.

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Well from my little knowledge of heads and horse power. Power comes from airflow- airflow is achieved from the design/dimention and size of shapes and tunnels etc inside the head. Now i dont understand how the material used could/would make much difference. Anything you can do with an iron head you could do with an alloy.

Same with valve size, anything you can do with an iron head you can do with an alloy.

The only things i can think of that may posibly cause a difference. Heat Alloy and iron generate/disapate heat at different rates.

Compression. Iron is probably a stonger material than alloy so would take a lot more to bend (not bend but you know what i mean). So my logic is an iron head may possibly get a better seal on the headgasket than an alloy one.

I maybe completely wrong in some of my ideas but at the time fo writing this it seamed to make logical sense

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I believe steam engines are better than internal combustion engines.

Anyway hands up who like alloy heads? F1, Speedway, and Drag Queens, Toyota, Holden. Honda, Ford, Mazda ..............(small & large volume)

Those against: GT Mowog,

Gee TK where did I say I didn't like alloy heads? There are some very good reasons and uses for them, I once made one in alloy, but for HP, alloy ain't it.........

OK.....OK......I'll leave you to play with your steam engines then.......

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"There are some very good reasons and uses for them, I once made once in alloy, but for HP, alloy ain't it......... "

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EDIT . Lillee, all cars made now have alloy heads, they get serviced, no problems with stripping spark plug threads.

I didn't say all alloy heads were bad, we were talking about the original 5 port alloy head that the original poster linked are we not? or are we talking about f1? I have no idea sometimes.

Regarding the original posters' link to the ebay head: Call GR, he says these "el cheapo" heads are cast from pretty soft alloys. You get what you pay for... Alloys aint alloys...

By the way I wasn't referring to the 7 port heads being bad value for money, they are great. I was referring to the alloy 5 port heads...

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Lillee - 1969 Morris Mini K

No, it wasn't you. Someone else chimed in with an unsubstantiated post about cast iron being the ultimate for retaining heat in the combustion chambers

The mechanical strength of the spark plug thread is more than adequate in both the 5 & 7 port versions. Cross threading is really a user error even if it were made of cheese.

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Too many cars, and too little time.

These 5 port alloy heads and the 7 port heads are both made by the same company "Pierce" and cast in the same aluminum .

I don't know about being "el cheapo" ,the casting on these heads is a way better than some of the other A series 8 port alloy heads I have seen.

I think you will find that the aluminum heads are less desirable than iron heads to work on due to tendency to clog tools ... so it may well take a lot more time to port them if you have tools for doing iron heads.

If you don't want a aluminum head on a A series that is your choice , but as you all know you can not buy a brand new iron head anymore .Aluminum heads on A series is going to be coming to the future sooner not later.
Some one needs to make a Aluminum A series block ...

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Just cause it says it is for a mini ,doesn't mean it will fit a mini......

Noone is saying that one is stronger than the other. Both are made the same and both are relatively soft in comparison to say the Elder 7 port or many other alloy heads out there.

Many agree the 7 port in question is a VERY VERY good price for what it is and is in a class of it's own. The 5 porter on the other hand, there are still plenty of the iron heads out there if you know where to look...

IT WOULD SEEM that people think I am against buying these alloy heads. Lets be clear, I don't give a rats ass how you choose to spend your money. I am simply saying, buyer beware. There is a reason why these Pierce casting heads are $1000 and why a Ken Elder is $3000. Yes these Peirce heads are very darn good value for money I completely agree, but you get what you pay for. I don't want youngins to go out buying any alloy head thinking they are all the bees knees and all are equal. PLEASE STOP THINKING THAT I AM TROLLING ALLOY HEADS!

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Lillee - 1969 Morris Mini K

I've been told by someone who has an alloy 5 port that on his the valves are spaced further apart (bigger valves can go in) and that engine cooling is improved.

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As Lillee said, there were problems with the original Pierce 5 port A series alloy head with studs pulling out, heads warping etc.
Whether their new 7 port head is cast in a stronger alloy, I have no idea. I hope so.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Down at Wakefield the other day I was talking to Fred Sayers and he was showing me his Sports Sedan with anew old stock alloy head with a rocker stud pulled out of it.
He said that he usually fits inserts into the stud holes but because this head was brand new and the thread had never been used he wouldn't bother.
I think he will fit inserts from now on!

{Off topic, it was great to catch up to Fred, I hadn't seen him since the early 80's. He is a real character!)

Yeah, I hate nothing more than an unsubstanited claim.

So while some one "substantiates" the claim that Aluminum is in fact better, with more data than "all the current manufactures use it"....Here are some basic facts for ya'll to chew on....

An Internal Combustion Engine, is by definition, a Thermal Engine. That is one that converts heat into useful working power.

To get the most power out of an internal combustion engine, you require:

Mechanical Efficiency

Volumetric Efficiency

Thermal Efficiency



Mechanical efficiency, is based on how much power is lost to friction in moving parts of the motor... the less loss the more effective.

Volumetric Efficiency has been done to death and needs no explaination

Thermal Efficiency is how effectively the engine converts the heat from the combustion process into useful working power. A typical petrol engine will only manage about 20-25% thermal efficiency.. Disease-als will do much better...

So.... for 100% Termal Efficiency (TE) we need 100% of the heat generated to be turned into power at the flywheel (or wheels even).... but heat is lost left right and center throught the motor... as mechanical friction,, heat into the cooling system,, exhaust.... AND straight out of the sides of the motor... as in heat that radiates out of the engine through the block.

Regarding that last part, one of the biggest factors is the "Thermal Conductivity" of the material the motor is made out of.... (also things like combustion space finish will most likely have a slight impact too),,,,


Thermal conductivity is measured as W/m-K (Watts per Kelvin Meter).

So a material with higher thermal conductivity, will displace/obsorb heat from one side of itself to the other faster, more effectivily and with less resistance....

The thermal conductivity of the Aluminum that most heads are cast from is 181 W/m-K

The thermal conductivity of cast iron is 80.4 W/m-k


So which one of these is going to let the most heat escape during engine opperation. Which one is going to lose the most heat. Which one is going to hold the most in.

.

I don't have a 5 port Al head and a 5 port Iron head of the same exact same spec... nor do I have a dyno sitting downstairs.... So I can't tell you if that differnce in Thermal Conductivity will result in more/less power.... I'm not about to make any "unsubstantiated claims".... I'll leave that to you guys.
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So, does anyone have a technical reason as to how Al heads produce better Mechanical, Volumetric or Thermal efficiency??????? Thus resulting in more power??? Or is the just another case of "well everyone else was jumping off the bridge so I thought I shoud too".....

<edit> Just for the record, if I was going to make a head, I would do it out of Al for cost and fast machining, and quick polishing.... basically finished cost would be much lower

and answer the O.P.... sure, I'd try an exotic head... I'll try anything once, and if I like it I'll do it again but seriously, they're cheap enough these days... and its no secret that the power in these motors is locked up in the head

Oh Cool, another crank thread

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Master of the Moggie Army & Founder of Awesomestock2010