Roller LA Deck Height

rustycowll69 said
am I missing something here? are you concerned about 0.014" difference in deck height? It seems like a lot of hand-wringing over such a small amount of material. I'm not an automotive machinist, but just a minimal clean up cut will probably take 0.004", another 0.010" doesn't seem like a big deal to me. It's not like cutting a sl/6 an 1/8".

Rusty, I don't think you're missing anything, other than that this is less hand wringing and more trying to get ahead of what combination is going to work well with this block. .014" difference is significant when talking about quench, though likely less significant from a general machining perspective. I'm an engineer with background in combustion, but not a machinist, thus familiarity with one concept leads to questions in another. 4.0" bore piston availability seems to fall into three camps: Stroker pistons, LA pistons for open chambered heads, and Magnum pistons for closed chamber heads. The deck height and balance differences in the Magnum engine complicate piston selection for an LA closed chambered head build while meeting both ideal compression ratio and quench. It seems easy to build either a motor with good quench, or a motor with good compression, but not both.

Bobzilla said
If you are worried about that, Sealed Power H116CP pistons are 1.66 compression height, would sit about .012" down the hole, and would bring the compression down to about 10.18 with 4.03" bore.

CHRYSLER Speed Pro H116CP 30 Speed-Pro Hypereutectic Pistons | Summit Racing

Edit to add, I have a 92 LA 360 block I just assembled. It was previously decked an unknown amount by previous owner to raise compression. I had it decked again to get a smoother finish and after we took off .012" my IC742 pistons only sit .018" out of the hole. So I highly doubt the 92 LA block is shorter than an older LA block.

Thanks, I had overlooked the H116CP based on small piston relief size without noting the compression height difference. This would likely be a better choice with no deck work being conducted, although it might not lead to good quench without a thin headgasket, thus raising compression again. I imagine I will end up having the deck worked on at least somewhat, if nothing else to square up the bores. That being the case, the small piston relief may be a liability in a motor built for quench (excessive compression for pump gas).

Thanks for the personal experience shared with the 92 LA block. That's what I was hoping to gain by posting here. One would logically assume that LAs would be the same, but there were other oddities with the 91-92 blocks (oil filter boss in 91, and engine mount pads in 92) that were introduced prior to the Magnum in 93. Some other posts I found claimed either that the deck height spec was revised for these late roller blocks, or at least production tolerances had tightened to the point where the motors were more closely held to the blueprint specifications. I appreciate the feedback, and would be interested to know more about your build process/combination with that 92 block.