friend needs some help with his honda

[440speedrider]

i have a buddy that has a 400 ex, he sent the motor to a the local napa machine shop to have a 440 kit put in it, he got a brand new head, new titanum vales and springs, when he got it back it ran fine for about 45 min and then it blew a head gasket, and if it runs for about 10 min it will blow a head gasket or the spark plug, any ideas what wrong with this honda? thanks for the help also someone told me earlyer that the sleve may have moved up or down and they will have to mill it flush with the top of the cylinder would this fix it for sure or could their be many other posibilites?

[nosliw]

did they install larger head studs? what compression is he running?

[440speedrider]

no larger head studs and im not sure of the compression

[2001-400ex'er]

How hard is it to install the head studs?

[85atc350x]

SHould have gotten heavy duty head studs installed. Big bore 440 kits are famous for blowing head gaskets if you dont change the studs.