Ya header side This is a proper angle formula for the people it should apply to all combustion engines,if you have a place to measure from,thats were the jig came in and took for ever to get some results,If ya been following me and word on look out world i got some pics,got like 7 runners and about 16 total,in various states of disrepair,Wish i started with the people first they get most of my attention,got 4 honda aeros 50 to 125cc and a real dio from canida,titles are a problem here.(parts is parts) This is my full time hobby im all busted up,can't hold a real job do to injeries,i used to ride dirt mostly but cant get my leg over the seat any more let alone the back problems,had to ride so the switch to scooters and love it,my little sence of freedom and the work keeps me half sane