Johnny listen too them....

The different valve angles are for more exotic applications. The general design was 23 degree while racing/nascar uses more 18-14 degrees stuff. This help promote air flow less restricted in the rpm range intended for use.

Also any change from 23 degrees will require special pistons (different releifs)

I agree with Tech on the 190cc heads for street. If you go too big on the cc's it's just the same as using too big of cam....

If you are using this vehical on the street I would strongly suggest the Edelbrock RPM AIR GAP manifold. One you gain slow speed torque and you need that.....Two it makes in most cases as much hp or more than it's single plain counterpart againts the old design! you'll be much happier