My 550 is being relinered with Darton DI liners by Steve Demirjian, and I'm running the numbers on whether I need to move the piston pin heights to compensate. Reason being of course that the stock Ferrari system has the liners sitting proud of the deck by 0.03 to 0.08mm and with the Darton's the liners will be flush with the deck. Too, the deck surfaces will be machined down just a tad to make them equal (currently the left bank deck is about 0.005" higher than the right), and to ensure the liners are flush.
Original "as found" block deck heights w/o liners:
Left:...........7.915"........201.04mm
Right:.........7.910"........200.91mm
Rod length:...5.157"........131mm
Stroke:........2.953"..........75mm
Pin Height:...1.299"..........33mm
So figuring what the theoretical assembled height is of the stock piston at TDC, I have 7.933" or 201.5mm, which is taller than the actual deck heights w/o liners, and still a bit taller than the deck with liners. So for the stock setup my piston is "out of the hole" by about 0.5mm.
Once the new liners are installed, we're shooting for these final block deck heights:
Left:.........7.905"........200.79mm
Right:.......7.905"........200.79mm
I'm not changing the rods or the stroke, so the only dimension I can change is the pin height, and on the old Mahle pistons, the top of the pin was nearly at the oil ring groove...... So if I want to limit my piston to being no more than 0.5mm out of the hole, I'm going to need to raise the pin about 0.21mm, and possibly squeeze the distance between ring grooves or squeeze the ring heights. That or go with thicker head gaskets.......or just leave the pin height as is and take a chance
Thoughts?
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