Please help!

[Fastest1here]

I have a 400ex with a 440 big bore kit. When I assembled the motor I used a Cometic Head Gasket and it worked fine for about 2 months then it blew out. My question is who else makes these head gaskets? I know by going to the 440 kit my cylinder is 4mil bigger in diamiter so im not sure if I can still use a stock head gasket.

Please help!

Thanks,

Jim