hi lads

building a cosworth na at the stage of working out the comp ratio using this site as a guide http://chainganger.co.uk/Page2/Page2.html now i am using accralite 92mm pistons high comp ones as shown on burton power which say it gives an 11.8:1 CR but on accralites site it says 12:1 so thought i best check it now using the site i mentioned earlier i put it in excel to make the calculator work and it came out with 15.03:1 which is way to high i need to be about 11:1 so i gotta skim the pistons down to lower the comp ratio has anyone else built one of these engines and had to machine the pistons or have they fitted em off the shelf and went with it????

cheers for any help

stu