In a message dated 1/28/2008 1:02:18 PM US Mountain Standard Time, mplindahl@xxxxxxxxxxxxx writes: FYI, I am using the newer style, open-chamber heads that I was told are desirable for the gas these days. The head surface was machined to guarantee flatness Years ago when I built the 413 for my 300K I scoffed a pair of recently rebuilt heads off of a 440 that was to be a race engine. The problem, I later found out was that the compression was lowered way too much in changing from a closed-chamber head with steel shim gaskets to an open chamber head with composite gaskets. Although the car essentially runs fine, crossrams and all, it has never had the guts to really pull the car hard. ( just ask don Cole LOL ) Later calculations indicated that the compression was dropped from around 9.5:1 down to around 8:1 with a corresponding loss of torque and HP. Several experts have told me I killed a minimum of 50hp. The bright side of the picture is that the car runs all day long on 87 octane garbage with nary a hint of detonation. When this 16 year old engine gets redone again I'll be going back to the closed chamber heads. If you must use the open chamber heads you already have please consider using the oem style steel shim gaskets so as to mitigate compression loss. Mike Laiserin Phoenix, AZ **************Start the year off right. Easy ways to stay in shape. http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489 [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/