Hi guys, im currently running in my newly rebuilt 4x4 engine. only done 150 miles was running sweet starts and drives fine, still starts fine now, BUT the other day I just jump in the car to pick someone up and driving through the village at roughly 20 mph, the cars engine tone changed like a deep bass line going off, the car juddered miss fired, i took it 200 yards down to my garage popped the bonnet and the whole water system pressurised the water pipes were solid nearly. Undone the header tank cap slowly and there was massive pressure build up. and the smell from the exhaust was immense. now the engine is a stage 3 and has been built to that spec and more. No expense spared and uprated everything, new water pump new oversized pistons, 4 layer wrc gasket new rad new turbo new uprated oil pump head overhaul you name it. it seems to me the head gasket has gone but how?????HELPPPPPPP