Im running a 351 cleveland with 302 closed chamber heads.The 2vs have been port matched,fitted 4v inlet and exhaust valves and the chambers have been slightly opend up .With flat top pistons and running on 98 octane it still pings its head off i thought i did all the things you do when u put them on a 351 but can someone tell me what else you have to do to em like what sort of chamber cc should they be /there proberly around 60cc/well the motor goes very well it revs to 6000rpm quite easy with a 750dp and 562/588 cam hyd.Thanx guys