11-23-2016, 02:07 PM
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CC Member
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Join Date: Feb 2006
Location: Gore. New Zealand.,
SI
Cobra Make, Engine: DIY Coupe, F/T ,MkIV.
Posts: 808
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Not Ranked
Quote:
Originally Posted by RodKnock
And from what Brent and others have said, aluminum shifts around, expands, squirms or whatever, which means that it leaks more? Alloy engines are rebuilt more often? They lose compression because of expansion? How much compression? Does an alloy block engine lose .1 pt, .2 pt, .3 pt, etc. of compression?
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BBM website.. Alloy block comes with nominal block height of 10.153", Iron 10.170", so Alloy block growth is ~0.017". With factory 1.73" rocker ratio that will cause an increase in valve lash of ~0.029". Thats the block alone without any further increase from alloy heads etc, obviously a problem for any solid cam with recommended hot lash of ~0.022" and would require block heater or similar to start up.
Iron 427 with 11/1 comp ratio will drop to ~10.6/1 in alloy block with same specs, so ~.4 drop in compression.
Brent would be better to simply add a hefty premium to every alloy block build and not waste his time trying to explain cause and effect to those clients.
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Jac Mac
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