I've never had issues ith the jetvalves, They always crack in between the valves.Even a njv caravan head is just as prone to cracking as the oem heads.
It comes down to either you want to pony up the money for a manral or magna head or you dont.

I had a rare marnal jet valve head, overheated it sooooo many times. We are talking pegged while drifting my old drift beater, and never bhg or cracked a head and it had a 18g on it.

Last edited by airbats801; 11/10/10 11:39 PM.
8 Starion SHP, 87 mitsubishi van, , 81 galant g54bt, 78 lancer g54bt, 1965 Mitsubishi Debonair Deluxe
87 swb montero offroad pkg goin g54bt with sr locker 33x12.5 dual bouncy.