AAC vs ABC
Have two 421p aac sleeves split at ports niether saw temps above 240 both great running engines very high rpm. Replaced with factory ABC and head no further problems and will tolerate higher temps still would not recommend.Have tied palmaris BRB sleeve in r1wc works very well,the motor I was speaking of is his twelve with its one piece sleeve casting the new collari "sirio" is the same style.