Can anyone hekp, happily putting my heads back on last night, came to bolting the cams back on great thus far, then Snap i have stupidly snapped the two main end cam bearing bolts clean off leaving a bit of the thread left in the hole, now they arnt overly tight as the wrench never hit toruque which was supposed to be 20NM's however this is ok for the rest of the cam bolts but a realised that these two end ones were thinner so i now realize 20NM's is way to much however can someone recommend a method of getting these out, dont want to take the head off again as i have just put the gasket on and set the bolts to correct tourque, and dont want to get a new head too much money all ready spent, options open to me please advise

cheers