Hi, i have been helping a mate rebuild his h2, we have come to set up the timing and re install the cams etc, we are useing a haynes manual and all seemed to go as in the manual, but when we turned the engine over with a spanner on the crank, the piston was hitting the valves and stopping the engine from turning, so we re checked everything, timing marks, correct number of links etc and it still wasn´t right. so we dismantled the cams etc and took out the plugs and saw that pistons 2&3 were at tdc?? We have another engine which we have compared it against and the other engine is right with the timing wheel at tdc number 1&4 pistons are at tdc. My question is does anybody have any idea what might be going on? is it possible to set the engine up with a different firing order? Any help would be gratefully apreciated.