If i remember reading the teds article correct you take the distance removed from head, deck, and gasket subtract .035 and multiple whats left by 1.4. using teds example: .065-.035= .030 x 1.4= .042.  your nearing the point where mill the intake would be needed but not yet there.
seth

If your pistons are .010, and your head gaskets have a compressed thickness of ,046, your quench is .056, just barely short of the recommended maximum of .060. 

Thanks Ted and everyone for the comprehensive explanation regarding milling cylinder heads and blocks. When I rebuilt my engine about 11 years ago it was quite difficult to fit in place the valley cover and also the intake manifold barely clears the valley cover. That's because I didn't  take into consideration the added thickness of the composition head gaskets.    .023" was removed from the decks and .010" from the G heads for a total of .033".   So, .033 X 1.4 = .0462    The machinist and I didn't feel comfortable milling that much stock from the intake surface of each head so only removed aprox. half that figure give or take a couple.   In reality, there shouldn't have been any stock removed from the cylinder head intake surfaces at all.  If I rebuild another Y-block engine, I will seriously consider custom pistons by adjusting the compression height accordingly and remove only  enough deck metal to true it up. I will admit I have no experience ordering custom pistons though. There has been no issues or leaks other than the valley cover being very difficult to install with out distorting it.  The pistons in this rebuild were cast Silvolite and the final dimension being .010 in the hole.  



64F100 57FAIRLANE500

The decks are reasonably thick but the intake manifold fitting properly to the cylinder heads becomes a problem if milling the block decks and/or cylinder heads excessively.  Also of concern are head bolt lengths as the threaded holes within the decks do get shorter as the decks and heads are milled.

I have cut the decks as much as 0.065” without any issues on a pump gas friendly 500+HP performance Y.  Anything more than 0.035” total cut of the heads and the decks can require some machining at the intake side of the head so that the intake can fit properly to the heads.  I always prefer to cut the intake side of the head rather than the intake manifold itself as cutting the intake manifold makes it specific to using with excessively milled heads.  By cutting the intake side of the heads, any stock and/or non-machined intake manifold can be used without concerns about fitment.

In the above case where 0.065” was removed from the decks, the intake side of each head was milled 0.042”.  When going with composition head gaskets, you do get 0.035” leeway on not doing any intake side of the head milling simply due to the thicker composition gaskets raising the heads versus using the thinner OEM steel shim gaskets.  In the above case, the decks were milled an additional 0.030 and that number multiplied by 1.4 gives the 0.042” amount in which to mill the intake side of the heads.

Lorena, Texas (South of Waco)

But is it square? If it isn't square or the surface smooth, you might have head gasket sealing problems. Using a composite gasket, like Best, will help, but it will also increase the quench, possibly to an unacceptable limit. 

Thank you for the help. Deck height looks okay based on the 9.7 I measured. 

You have to consider that anything that is mass-produced will not be exact. 

The Y block has successfully been milled to 9.740" deck height and lived quite well.  The heads measure 1.000-1.011" if uncut at the pads on each end.  Joe-JDC

JDC

If you look on the exhaust side, near the spark-plug holes, you'll find pads the height of which can be measured to determine whether the heads were ever surfaced after engine assembly. The pads should measure 0.999-1.001, if the heads have not been milled. 

Good question. Zero-decking the block is not uncommon, but the compression/pin height of the pistons being used needs to be taken into consideration, as well as rod length and stroke. The nominal compression/pin height for the original cast pistons is 1.768 for 292s & 312s. On the other hand, my Autotec forged pistons have a compression height of 1.780. Ted, John, or Joe probably can provide a nominal number for the block-deck thickness, but no two blocks may be exactly the same.