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I was looking at the lrd perfromance website this evening, and I noticed that they had an 11:1 kit for the 400ex. The kit included a piston, gaskets, and a cam. How does this change the compression ratio without changing the crank or piston rod. Is it all done with the piston, or do the gaskets have something to do with it.

It would be greatly be appreciated if someone could explain this and help me understand how some of these engine mods work.

Thanks in advance, Scott #84
 

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Im not a professinal at this, but ill give you my best awnser. The piston is simply moved closer to the head. Higher compression doesnt really mean more air comes in, it just means that the air is more compressed before combustion.

Can anyone tell me if im right?
 

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to elaborate a little... the top of my 13.8:1 piston has a dome with 4 depressions for valve clearance as opposed to the flat top stock 10.5:1 piston. when at TDC (top dead center), the higher compression piston rises above the plain of the cylinder whereas the stocker stops dead even. does that help?


almost forgot... the new gaskets are oem stock and so are the new rings. no change to the crank or connecting rod. it's an easy piston swap.
 
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