Block deck shaving

[scott]

In your opnions, how much can safely be shaved off the top of a block. Any difference b/w aluminum and cast iron?
Thanx
-S

[Jac Mac]

Hi Scott,
This is a question that can have several answers depending on which block or engine family we are discussing,and why do you need to remove a large amount?
Alloy blocks have to be treated with some caution when removing large amounts as this can reduce the strength of the retaining lip on the sleeve which sits in a recess at the top of the block bore.Also most alloy blocks have the sleeve installed slightly proud of the deck surface to aid gasket sealing and any set the sleeve may have after installation.
Most of the production cast iron blocks can stand a reasonably large amount(0.050")without any structural problems,However pushrod length and rocker arm geometry will be affected with amounts as large as this along with inlet manifold port match and valley gasket clearances. When you take all these factors into consideration it will probably be more cost effective to look into a longer con rod or a piston with a taller pin height.This way only a minimum of material if any will need to be removed.
Hope this helps.
Regards Jack

[scott]

Looking at a new aluminum RDI SBF w/ 0.1 inches off the deck. It doesn't really make sense why someone would do that to a new block though.
-Scott

[Jac Mac]

Hi Scott,
Sounds like someone made an 'oops' to me. Without knowing more about why its been done I would leave it alone. Any cost savings will disappear when you find yourself paying for custom rods,pistons,pushrods etc along with extra machine work costs to make the combo work.
Regards Jack.