Originally Posted by Hiro
hum...
not a lot of room to mill there specially if you use big valves,
then if piston protrudes too much the fire ring will sit high,
I don't know how to deal with this?
Hiro
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Yes, you have to be careful when you get to extreme CIH piston designs. There's a point where you just can't go any further with valve reliefs/raised rings/long rods. What happens is the intake valve reliefs will literally cut into the top ring land if the ring stack is too high, and if the piston crowns are made thicker to allow for the deeper valve reliefs and a long rod is used, there is the potential for the rod itself to hit the underside of the piston.
So in order to circumvent these issues you have to move the ring stack down a bit
and use thinner rings, possibly use piston pin buttons with an oil rail support and also use rods with a smaller pin end (say .826") and an equally thinner profile rod to allow for all these extra clearances.
I will say that it is theoretically possible to stick a 6.2" rod into a 1.9, but you're so on the ragged edge this way, it's best to keep the rod to around 5.7-5.8". With bigger stroke engines, you're relegated to shorter rods...maybe 5.4-5.45" at best...unless you do the diesel 'tall deck' block.
Bob