To use 426 pistons, you would have to deal with piston pin location and rod length compared to stock 413 pistons/rods. Likely the same, but ya gotta know. Ray On Jun 2, 2007, at 8:28 PM, John wrote: From Allpar.com: "The 413 saw a 4.18 inch hole which directly resulted in an easy leap to the NASCAR limit of 426 cubic inches by boring the block to a 4.25 inch diameter." So it would seem that 4.25 - 4.18 = .070" - If a 413 block could be bored .070" with no problems, standard 426 pistons may be able to be used. I've never done this, so I don't know if it's safe to do so. John Spiers Lake Worth, FL [Non-text portions of this message have been removed] To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! ID required) <*> To change settings via email: mailto:Chrysler300-digest@xxxxxxxxxxxxxxx mailto:Chrysler300-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/