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2002 Aluminum Cylinder Head Alloy


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1 hour ago, Son of Marty said:

Back in the day all BMW would call it was "white aluminum alloy"  probably to make people think it was special.


Nowadays, people use the word billet, to make aluminum parts seem special.  (not cast parts, obviously)


While we're waiting for more answers, I'll add another question.

Which aluminum filler rod works best when TIG welding on a head?


I'm most familiar with 4043 and 5356; the former being much softer and less prone to cracking.



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Thank you both for your reply.

I was assured that the alloy was 2024. I know European automakers like 356 alloy.


I will ask the last welder on this project which rod he used. He said the rod flowed in nicely.

Three amazing welders have worked on this head.


The head has been extensively welded and modified so it needs to be heat treated.

The Metallurgist needs to know the alloy to properly program the treatment. 


This is the article off my web site that I wrote about my work on this cylinder head.

The article was originally written for the MotoIQ website


Thank you again.



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What I don't get in your writeup is:
Why the whole work without increasing Valve diameters - no one would build an "all in" engine without larger Valves?
Even for a street engine you'd increase Valve sizes to 47/39
The top engine guys here in germany have to weld parts of the ports in order receive best results.
Also is the 121 head the better starting point for a Hemi Engine

Edited by uai
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5 hours ago, uai said:

Why the whole work without increasing Valve diameters - no one would build an "all in" engine without larger Valves?


Worth mentioning: Some of the vintage race organizations here in the US require stock size valves in the M10. Likewise, rules state material cannot be added to the ports. (No cheaters, right?!) -KB

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13 hours ago, Replika999 said:

I was assured that the alloy was 2024

That can’t be right for a cast cylinder head. 2024 is a high hardness, high copper, heat-treatable wrought aluminum alloy. It’s not a casting alloy.


The Aluminum Association alloy identification system employs different nomenclatures for wrought versus cast alloys. Wrought alloys use a 4-digit ID system (like 2024 or 7075), whereas cast alloys use a 3-digit decimal point ID system (like 204.0 or 319.0. or 356).


Cast Aluminum alloys are designed specific to the casting process being used to form the parts. Completely different from wrought alloys in sheet/plate and billet forms.


The most common (90%} cast alloys are the 300 series Al-Si based alloys. The most significant reason for alloying Silicon with Aluminum is to improve the cast-ability by making the molten metal more “fluid like”.


The most common High Pressure Die Casting alloys are 380, 383, 384 and use Si, Cu, Fe, Mn and carefully limit Mg.

The most common alloys for sand casting, gravity casting and low pressure casting are 356 and 357 (6% and 7% Si respectively).

If I were to guess, I’d suggest 204, 319 or 356 as the alloys possibly used for the cylinder head. They were available in the 60s-70s.


Ps: I’ve got a bit of experience and background with aluminum, being an aero engineer involved in the development and testing to create the 2195 Aluminum Lithium alloy used on the shuttle…

Edited by visionaut
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My question was about the cylinder heads alloy, so this is off topic.

However if you want to know about Air Flow and Volumetric Efficiency and not Porn Movies. Bigger is Not always better.

If your "Bigger Valve" is now shrouded by its proximity to a combustion chamber wall. You have done nothing except add weight to the valve train. The shape of the port runners and the combustion chamber are the primary factors in determining VE. The critical areas in this equation being approximately one inch or 25MM either side of the valves seat. The valve, port runner and the combustion chamber need to work together to complement each other.  

Most people look only at a cylinder heads Max Lift CFM. This tells you very little about a cylinder heads overall air flow capabilities and even less about the engines possible usable power and drive-ability.

The 2002 BMW head was not a milestone in cylinder head design. In order to get the improved overall CFM numbers, while also increasing port velocity. I spent a lot of time on my flow bench in order to find an improved and re-shaped combustion chamber. That is what makes this cylinder head work. Not larger valves or bigger ports. That may work for some cylinder heads. It does not work for this one.


Thank you for your response.




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11 minutes ago, Replika999 said:

Thank you Kugelfischer. You are the second shop that said 2024.

I did some machining work that ended up on a few of the Space Shuttles as well.


Cool beans!!!

Thank you again,


Don, if you’re referring to me, I said the head can’t be 2024… and no one has responded concurring with 2024 here.

My thoughts were 204.0 or 206.0 if it’s Al-Cu. 356.0 if it’s Al-Si, or 319.0 if it’s Al-Cu-Si.



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I don't have a ton to add beyond 

that it does weld and flow, and, critically, bond to weld very well.

Many castings don't like to reflow- an M10 head has no problem,

and the transitions from weld to castings look really good.

I played with a few chunks of casting just for shiggles, and

while I'm a terrible GTAW wielder, the material was very forgiving.


On top of that, there's almost no porosity, so the chances

of hitting an oil pocket are very low.


I'm guessing you're stress relieving and normalizing it?


As to the valve size, if you are willing to go well over stock lift,

flow will increase with seat size, as the shrouding's reduced as the valve

moves away from the cylinder wall.  I dinked with it a little, but am rules-

limited to the larger stock size, so didn't go far.   


If the metallurgy really matters that much, analysis is always possible...

'cause I don't recall it ever coming up, here.




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