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i am over boring a N42...probably just .50mm i was looking at MSA and noticed they have stock pistons for 60.07, and "preformance" pistons for 53.00 they say the performance pistons: "these cast flat top pistons have raised domes for higher comp ratio" ??? are they the same as flat tops? I am going to be running them on a shaved .080 P90....anybody have experience with these "performance pistons"

thanks

jon
 

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No, I don't think so because if the piston had dome than it's dometop. If you have P90 shaved .080" than you have about 44cc chamber right? flattop should give you about 10 to 1 compression. So you shouldn't need the dometop unless you're going to run race gas. And what's your cam? Max lift on stock height head with flattop is .500" so minus .080" give you max lift of .420". This can depend on the thickness of you head gasket too but you may need valve reliefs on the pistons.
 

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dome pistons are like the top of aice cream cone before the first bite i have a set of dished pistons .50 if you want e mail me
 

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I have a used both a P79 and P90, shaved .080, on my flattop motor.

If you put a straight-edge across the chamber, there's almost no clearance between it and the sparkplug electrode. So I had thought about going the MSA piston route too, but it's gonna be close.

If you look at the shape of the raised section on the piston, I suspect it was really designed for tHE n42/47 chamber.
 
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