Originally Posted by NCTURBOS
Is the valve spring clearance issue in the head retainer-to-guide or spring diameter to casting? Or?? I was hoping with how well the M8 heads seem to flow (based on #'s I've seen on the boards) that a low lift camshaft with proper timing events could accomplish it... I'm not really looking to crack open the top-end of my new bike just yet.
Thanks for the input!
The spring itself will limit the lift numbers. If your willing to change those, it opens more room but the next thing that comes into place is piston to valve clearance. Very few springs out right now and the ones that are raise the spring pressure and IMHO that is the wrong thing to do on this engine for street use. This is a 4 valve engine that uses a single pushrod and lifter, so we double the spring pressure to start with stock. The stock spring is about
67 lbs on the seat and 200 over the nose, so you double those numbers and we have about
134 and 400 over the nose being applied to the rocker arm. IMHO that is plenty for the weight of the valvetrain. These are the limits to making power with no head removal.