Decking a 496 Block

[koutroul]

I have a 2004 Mercruiser 496MAG 375hp with broken rod,piston and damaged cam that I am trying to rebuild. Mechanic took block to a machine shop to bore it 030 and deck it and the turner said he bore it 030 inch and mill out the deck by 020 mm. I ordered Wiseco pistons PTS524A3 (Compression height 1.340inch) and the CH6700APRB8-A (length 6.700 inches) rods and now that they installed them the found that at left cylinders the piston heads are out (over the the deck which is dangerous) by 020mm and on the right cylinders by 010mm so I am thinking that he may removed more from the deck and also not equal amount.
How can I found the compression height of the old pistons (i found that rods are 6.693 inches but cant find the old pistons CH to compare if the change of pistons/rods created the issue).
Also I can not find the thickness of the original gasket (I bought the full gasket kit from Mercuiser and its the same gasket for the standard and oversize pistons but I cant see compressed thickness anywhere.
Is these clearance a problem and I must use thicker gasket. Also I know that he machined the heads too, to make them flat but again I can not know how much and even if I ask I am not sure he really knows.

Also in some manual for the GM L18 powertrain I found that Deck height is 10.231-10.241 inches:
www.kohlerpower.com/onlinecatalog/pdf/tp6105.pdf

I found that Cometic is making thicker marine gaskets but cant understand if I need one and which one.

[cgarb]

Is the piston proud of the deck by .010 and .020mm or thousandths of an inch? .020mm is only around .0007"...nothing to worry about. Thousandths...probably still not that much of an issue. Just figure out what the stock head gaskets are compressed and like you said order Cometics that are .010" and .020" thicker than what you had and that would be like having a zero deck engine.

[PackardV8]

And yes, it is common for the height of a V8 block to vary from side to side and corner to corner on the same side. That's why we use a BHJ fixture and "square deck" every block.

[Alan Roehrich]

If the pistons are shelf stock and you haven't scratched them, see if you can send them back, and just order a custom set, they won't be much higher. Also, send the block to a competent machine shop and have the decks corrected. And everything else checked.

[Merc Man]

Both Sealed Power H880CP (pressed pin) and H1134CP (floating pin) lists as 1.350 Comp height.
I have used the H880's without any issues.