It is engineering legend (may or may not be true) that the spec. for 356 was
created (or at least tweaked) after WWII to describe what you get when you
melt down a B17 ! For a few years the market was flooded with surplus alum.
The T-6 refers to the heat treat, T-6 being an artificial aging process that
considerably improves the mechanical properties of 356. I cannot imagine a
356 block melting, even on nitrous. But if you exceed the critical
temperature of the artificial aging process (somewhere around 450 degrees...
my memory leaks) the material reverts to it's native properties, softening
considerably. But this is also true of the other T-6 alum. alloys.
Greg
-----Original Message-----
From: owner-land-speed@autox.team.net
[mailto:owner-land-speed@autox.team.net]On Behalf Of ardunbill@webtv.net
Sent: Friday, June 08, 2001 2:42 PM
To: bigsid@webtv.net; marco; bjgayle@aol.com; clemtebow@jps.net;
land-speed@autox.team.net; IfixMGs@aol.com; cometkim@yahoo.com
Subject: Arduns, and Aluminum Casting Alloys 355 and 356
Hi Folks, you recall we recently had some discussion about the new GMC
270 HP Inline Six, a story about which appears in the June Hot Rod
Magazine.
One point was about today's casting technology. The article says the
new GMC's block and head are cast of A(Alcoa?)356-T6.
As most of you know 356 is used in lots of today's high-quality racecar
aluminum castings.
Back to 1947, Zora's original Ardun literature says his Ardun heads are
made of "Alcoa 355 T-6" material. Machinery's Handbook lists both 355
and 356 as high-strength casting alloys now.
As a dedicated Ardun man I always wondered what the difference between
355 and 356 is. Nobody ever seems to know, or if they do know, they
don't say. Until today.
In the June Hot Rod also appears an ad by World Castings Co. They make
Merlin blocks and heads, iron and aluminum, and from what I can tell,
they are a leader in the aftermarket industry. Their ad says their
big-block Chev heads are "high-density 355-T6".
So I sent an e-mail to them, which is forwarded below, and their
response is also forwarded below. They say 355 is better than 356. If
so, I guess this means Zora knew best. We have some insiders from
today's automotive industry that know this stuff, on the List, so I hope
they or any other aluminum casting experts, will comment. Cheers,
Ardun Bill the Curious, in the Great Dismal Swamp, Chesapeake, VA
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From: wrhoddinott@webtv.net (William R. Hoddinott)
Date: Fri, 8 Jun 2001 14:16:55 -0400 (EDT)
To: ardunbill@webtv.net
Subject: Fwd: Re: Comments about World Castings
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From: "Tech Support" <contact@worldcastings.net>
To: <wrhoddinott@webtv.net>
References: <004132003140761PRIMEDIA1@nt01.primedia.com>
Subject: Re: Comments about World Castings
Date: Fri, 8 Jun 2001 08:39:38 -0400
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Will,
the metal that we use is a stronger aluminum than the 356, this is why
we don't have to use a threaded insert in the castings. the 356 is a cheaper
aluminum and it is not as hard as the 355, also with some N.O.S.
applications this metal will not hold up and could possibly melt. I hope
this helps, and good luck.
Justin Hunt
----- Original Message -----
From: <wrhoddinott@webtv.net>
To: <contact@worldcastings.net>
Sent: Thursday, June 07, 2001 10:03 AM
Subject: Comments about World Castings
> Comments about World Castings from:
> ***********************************
> Email Address: wrhoddinott@webtv.net
> First Name: William
> Last Name: Hoddinott
> Question Topic: Tech Question
> Comments: Responding to your ad in the June Hot Rod Magazine, p. 105.
> Question for your engineers. Why do you cast your big block Chevy "Merlin
> Grumpy Lite" heads of 355 T6 aluminum (you call "high density") rather
> than the 356 T6 that everybody else says they use? Not merely a misprint,
> is it? I know from my Machinery's Handbook that 355 has been around for
> many decades, just like 356 has. Thank you. Bill Hoddinott, Chesapeake,
> VA
> ***********************************
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