Stepped Dish Pistons

[beanhead]

I have the forged ICON 842s (27cc dish). Do they calculate the dish volume from the top surface of the step, or the outer edge that surrounds the dish? I would think it's from the highest point of the piston...
Another question. They sit, by spec, at .010" in the hole. The plan is to get them to zero deck height. Knowing the "accuracy" of factory RB decks...if, by the time we mill and square the block, any or all of these babys are sitting proud would we have to mill the flat stepped part of the pistons some. (I hope not!) How much would taking, say, .010" off affect the volume/compression level? Would removing that hypothetical .010" of aluminum be enough to necessitate a re-balance? I just get curious about this stuff..Thanks!

 

[wyrmrider]

what heads?
get the decks square with good finish
if they stick up use a thicker gasket, no need to machine
If -.010 to 0.0 use the .028 mr gasket if closed chamber heads
on those you measure from the top
on the quench domes for stock heads not from the quench dome, from the lower deck

 

[beanhead]

what heads?
get the decks square with good finish
if they stick up use a thicker gasket, no need to machine
If -.010 to 0.0 use the .028 mr gasket if closed chamber heads
on those you measure from the top
on the quench domes for stock heads not from the quench dome, from the lower deck

I'm using RPM heads. I was curious how they measured these things as it seems the 'stepped down' portion of the piston volume would have to include the area around it, all the way to the cylinder wall, since that part of the piston is way down below the deck at TDC if that makes any sense...but I'm sure they work great or the designers wouldn't be making the big bucks! No big deal, just wondering thx Wyrm.

 

[dvw]

Dish volume is measured from the highest point.
Doug

 

[beanhead]

Dish volume is measured from the highest point.
Doug

Thanks Doug