We had an A12 that was happy to rev around 7,000 and that was just a bit of backyard port work and double valve springs. With a mild cam and 32/36 weber. it was running fine till i retired it for an A14. One day i pulled the head off and found Number 3 piston had spat the rings into the head like pickin glass out of wounds, yet it still ran fine. They are hard to kill the A series i miss me little A14 in some ways.