[cdowns]

heat goes from one head to the other heating bottom of the manifold to heat the gas mixture ,less time on choke better drivability at some loss of power// blocked off it gives you a denser fuel charge and more raw horsepower but with a loss of smoothness that a heated charge gives you// a somewhat happier comprimise instead of full open gaskets is 3/8holes in gasket allowing partial flow thru the riser