a couple of people, including ACL, make 3/4 grooved bearings for their "race bearings".
the problems are the same with 4AG & 3S as they both have simialr design faults
case 1) owners let the sump run a bit low, hard cornering causes mometary oil starvation, bearing picks up from metal-to-metal contact.
case 2) owners rev the crap out "old" engine. the oiling design causes momentary loss of oil flow from main to big end (oil flow is cut off due to crank oil gallery design) big end bearing fails from metal to metal contact.
case 3) combination of 1 & 2. this seems to be common on drift car engines
the ACL race bearing helps with case 2 only ,as they allow each big end to be fed with oil from the adjacent main bearing, for a longer time at the critical point. they help stop the flow getting cut off instantly. the ACL bearings are very fussy on size. the tunnels have to be perfect to get the correct crush on the shells.
the factory fully grooved bearings (7A) are another solution, but they have lower load capability.
