340 Modifications

Not to stray to far off the original question but I really got into 340s and found it interesting almost every non machined high compression 340 I have seen are off on the factory rating of 10.5 compression-more like 9.2-9.8 range.Chrysler specified the compression rating based on the piston being .018 above deck and using the factory thin steel gaskets and small chamber heads.The head ccs are greater than the factory advertised,then you have the head gaskets wich unless untouched are now averaging .040 compressed,and every unmachined factory 340 Ive taken apart/inspected (69-72) had the factory pistons right at zero deck or a couple thousandths above.My machinist whos raced 340s for years intially told me about this.Regarding the cam my opinion is you couldnt go wrong with a xe-268 for the street-or for the real wicked idle a isky 270 wich has a 108 lobe seperation but moderate duration.