John,
Here's what I know. SC developed the first alloy head some years ago and it
was a good design but not perfect.
Mark Lambert of Tennessee, the Healey Club Technical adviser did an
evaluation of the four cylinder head and was quite impressed. He wrote an
article on the head plus I visited him at his shop and he briefed me on the
results.as follows...
- Normal power band on stock BN1/2 with iron head is 2500-3500 RPM. Power
band with alloy head is now 2200-4200 RPM. Double.
- Where you could barely get two fingers into the air passages with the iron
head, you can get a golf ball through the passages in the alloy one. Much
better breathing, which was the whole idea of the re-design.
- Mark claimed from his testing that a stock BN1/2 with the alloy head
(standard H4 carbs) would out perform a *standard* 100M or Le Mans converted
100, i.e. no ported and polished head, no headers, etc. The bigger H6 carbs
were just trying to force more air through an already restricted air
passages in the iron head.
Now on to Denis Welch. I spoke with Denis some years ago about his alloy
head and here is what he told me... Initially he used the same head from
the same foundry where SC had their head made. He found the head deficient
in several areas. He worked with this foundry and had his own head made up
to his specifications. Same basic head but with Denis Welch modifications,
plus DW offers three versions (standard, fast road, and full race.)
FWIW, there is no deduction for using the alloy head in Concours judging,
provided it's painted. Externally it's identical down to the original
Westlake patent numbers cast into the head.
Lastly, in my opinion, there are two types of original iron head. Those
that HAVE cracked and those that WILL crack.
Cheers,
Curt Arndt - AH Concours Committee
Carlsbad, CA
'55 BN1, '60 AN5 :{) '06 Cooper S
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