Is cylinder head aluminum alloy purity a thing to worry about?

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ELS
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Is cylinder head aluminum alloy purity a thing to worry about?

Post by ELS »

I have 2 engine heads for an engine, identical in everything apart for the alloy it's made from,
and I was thinking it I might have problems with the more impure alloy head, probably for sure in a turbo application but how about NA? with a high compression ratio, do I perhaps use the better alloy head instead?
or does it practically make no difference?

if you're wondering the aluminum alloys that it's made from, I found the specs for them:
Aluminum - 90.6 - 92.9
Copper - 5.5 - 6.2
Nickel - 0.8 - 1.2
Manganese - 0.6 - 1
Cerium - 0.15 - 0.3
Zirconium - 0.05 - 0.2
Iron - <0.3
Silicon - <0.3
Magnesium - <0.05

Aluminum - 88.1 — 93.5
Silicon - 4.5 — 5.5
Copper - 1.5 — 3
Manganese - 0.6 — 0.9
Magnesium - 0.35 — 0.6
Iron - <1.6
Zinc - <0.3
Lead - <0.05
Tin - <0.01
oh and idk of any modern standard alloys that fit these specs, since the alloys in question are russian standard alloys
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by BOOT »

Is one seasoned/used?
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by ELS »

BOOT wrote: Wed May 25, 2022 5:40 pm Is one seasoned/used?
both are
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by ELS »

reading more spec sheets, some say that the purer alloy also has a higher heat resistance, 350 degrees C compared to 275 of the crappier alloy, so I'll probably use that head then.
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by RAS »

Factory heads have improved a lot since the 60s. Porosity was a big issue back then. Today most aftermarket aluminum heads are cast in China. Brodix and Profiler are cast in America at their own foundry's. All Pro, Mast and a few others are also cast in America. Buddy Barr and a few other foundry's still cast here. Australia CID are cast at ProFiler, CHI are Australian. Higgins not sure about. Ever since Investment companies bought the high performance industry out a lot has changed. Much is no longer available because it doesn't sell enough to please the accountants of investors.If BRODIX sells out its over.
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by 1980RS »

From what I remember there were LS heads in late 01 to 02 that were crack prone. We had a few at the dealer I worked at and they has a big X on the outside bottom of the head.
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by mag2555 »

If you have the funds then I would send out the heads to be used on the Turbo motor and get the chambers heat barrior coated, and not a bad idea to get the piston tops coated also.
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by earlymopar »

What specifically are the 2 alloy grades in question and why are you referring to one as being "more impure"?
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by dannobee »

Interesting. The numbers don't seem to directly cross over to anything used in the west.

For reference, Porsche used two different alloys on the air cooled cars. "Y alloy," and "RR350." The RR350 alloy was reserved for turbo engines and is generally regarded as the alloy to use if you're going to race one. The Y alloy heads will crack under high boost racing conditions.

Unlike many manufacturers, they made it easy to distinguish between the two by casting the alloy type right into the heads.
FWIW
BC7C077E-B395-45F1-BDF1-19956CF83D7C.jpeg
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by dfarr67 »

I thought- I over think things.
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by ELS »

earlymopar wrote: Thu May 26, 2022 8:10 am What specifically are the 2 alloy grades in question and why are you referring to one as being "more impure"?
well the more impure alloy is that which has an overall less aluminum than the other... the 2nd one I described has 88.1-93.5% aluminum, overall lower than the 90.6-92.9
the less pure alloy is called AЛ3, the other - AЛ33
AЛ3 being the one with less silicon, and slightly similar to 6061
AЛ33 being the one with more silicon, and slightly similar to EN1706
dannobee wrote: Thu May 26, 2022 9:02 am Interesting. The numbers don't seem to directly cross over to anything used in the west.

For reference, Porsche used two different alloys on the air cooled cars. "Y alloy," and "RR350." The RR350 alloy was reserved for turbo engines and is generally regarded as the alloy to use if you're going to race one. The Y alloy heads will crack under high boost racing conditions.

Unlike many manufacturers, they made it easy to distinguish between the two by casting the alloy type right into the heads.
FWIW
BC7C077E-B395-45F1-BDF1-19956CF83D7C.jpeg
well the alloy without silicon I found that it sometimes was said to be similar to 6061, although they're still pretty different.
the other alloy was listed to be similar to EN1706
Last edited by ELS on Thu May 26, 2022 11:50 am, edited 1 time in total.
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by ELS »

The one from the alloy that is more similar to 6061 seems also a bit more porous.
al33 head.jpg
al3 head.png
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by earlymopar »

35 years in the die-casting, sand casting & investment casting industries (various grades of zinc, aluminum & magnesium). There are a large number of variables that can lead to porosity and all are related to the casting process and tool design.

Just curious with the reference to Russian alloys, what the heads are from and do you have any indication of how old they are?
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by ELS »

earlymopar wrote: Thu May 26, 2022 1:42 pm 35 years in the die-casting, sand casting & investment casting industries (various grades of zinc, aluminum & magnesium). There is a large number of variables that relate to porosity and all are related to the casting process and tool design.

Just curious with the reference to Russian alloys, what the heads are from and do you have any indication of how old they are?
they are from VAZ vehicles, one from a VAZ-2106 - 1.5L other from a VAZ-2121 - 1.3L
both are from around 1983, in winter it gets down bellow -20C and in the summer above 30, so the heads should be as seasoned as they can be.
both have a ton of miles on them, indicated by low compression, and flat camshafts.
although I only have one head that is from the AL33 alloy, the AL3 alloy heads are all more porous than the AL33 alloy head, but I only have one AL33 head to compare it to, reading the wiki page on 6061 aluminum, it says that it's harder to cast alloys with lower silicon content, so maybe that's why those heads are more porous.
the casting quality is pretty bad, in newer heads the writing is almost unreadable because the dies are so worn out.
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Re: Is cylinder head aluminum alloy purity a thing to worry about?

Post by BCjohnny »

There is little to no value in using 'purity' in assessing alloys ...... 'pure' Aluminium has few uses outside of electrical conduction

Both alloys have their advantages, the higher Si one is cheaper, easier to cast (with better anti corrosion properties) but harder to machine, the Cupro-Nickel one has better 'strength' (especially 'hot') but is harder to cast and more expensive

It's not that simple, but it's indicative ...... and leads manufacturer choice

As said porosity has more to do with processing rather than alloy make up itself

RR (RollsRoyce) 350 is a CuNi type 'high duty' alloy

I doubt there's little to choose in a NA application, indeed the 'harder' Si alloy might be a better choice, but ultimately the CuNi alloy is 'stronger' overall

Or something like that .......
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