a friend has this engine, 10.5-1 compression and other high performance mods. it keeps blowing the rear jug seal after around 5-10 G miles. any ideas to this problem?? thanks in advance, bo.

 

Base, head, or rocker gaskets????

 

are the heads perfectly flat,is cylinder flat.is he using right procedure to torque them down and what kinds pf gaskets.I use cometic religously never had problem.On evo I run no gasket just o-ringed the cylinders.On my my 127 ultima I run 12.5:1 with cometics no problems yet and making 158 hp at rear wheel havent hiot the bottle on that one yet but on 80 ci evo with no gasket even the bottle didnt phase it,well it pulled front end in 3rd gear but other than that.