[SEL] OT quesiton about cast iron

[bill at antique-engines.com]

Thanks for the info - that sort of matches what I've heard, and experienced.
I've always felt exhaust manifolds seemed to shrink and get brittle. Never
knew why.
I've also been told that supposedly AMC blocks have a higher nickel
content than any other auto makers blocks. Some dispute that with actual
SAE drawings and spec sheets, but the rumors persist.
One type head seems to crack along the back bottom edge near the corner.

I've also got a spare F20 manifold I've been thinking of fixing up just in
case something happened to mine and wondered how difficult it would be.
Had an exhaust manifold from a Regular welded up one time - they fellow
literally welded a cast patch on the back of it and it worked great! NO
cracks. He was good.

Bill

>
>
> Bill Dickerson wrote:
>> Assume automotive parts here in these questions:
>>
>>
>> A. Is the cast in exhaust manifolds different than the cast in, say, an
>> engine block or heads?
>
> Yes it is a different composition. Blocks have more nickel and silicon
> than manifolds.
>
>>
>> B. If different, are they higher or lower nickel content?
>
> Manifolds are lower nickel content than the blocks.
>
>>
>> C. Can one gauge nickel content by "the spark test", taking a grinder to
>> it
>> and watching the pattern and color of the sparks?
>
> Yes, BUT not without a LOT of practice.
>
>>
>> D. Is it easier or harder to weld an exhaust manifold than an engine
>> block
>> or head?
>
> When new they are about the same except the thinner walls on the
> manifolds make them easier to burn through, and stress cracking is
> harder to prevent.
>
> When used Manifolds get BRITTLE and tend to shrink from the constant
> thermal cycling. Blocks tend to relax and are usually easier to weld as
> they age IF you bake them to drive out any oil/coolant.
>
> I don't even attempt to weld some manifolds, Instead I braze them or
> replace them.
>
>>
>>
>> Thanks.
>>
>>
>> Bill
>> Runnells, Iowa, USA
>>
>
>
> --
> Steve W.
> Near Cooperstown, New York
>
> Pacifism - The theory that if they'd fed
> Jeffrey Dahmer enough human flesh,
> he'd have become a vegan.
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