Im new to the world of nitro, iv always run electric, had a HPI Rush roller laying around for ages and finally got round to rebuilding it, which i finished today. heres the problem part-

After finally getting the engine running i noticed it was getting pretty messy (fuel everywhere) so i stopped it.. i then realised the problem.. as i pulled the pullstarter slowly and looked closely fuel was leaking out between the engine block and cooling head, i removed the head, cleaned up the mess and put the glow plug back in place then screwed the cooling head back in in the proper way (top left screw, bottom right and so on so the preassure was equal) now iv dont this no leakes but the pressure seems too much, its hard to make the engine turn, like the pressure is too much for it to turn propperly.. if i loosen the cooling head it turns fine but then ofcourse there would be a gap again.. what do i do?