A blocked heat riser will not make it smoke! It may not have the power it should but it won't smoke. I would pull the plugs from the smoking side and compare them to the other side. You will most likely find one of them oily.
Two general rules of engine smoke I find to be true.
1) - If it smokes at idle and start up its the valve seals gone bad. The high vacumn pulls the oil through the valve seal and down the guide.
2) - If it smokes when under a load, its the rings. The rings are loose and at high rpm they can't seal to the cylinder wall which lets oil in to be burnt.
The valve seals are replaceable with out real major work. The rings will require total tear down and rebuild.
I change valve seals on my 168,000 mile Dodge 318. It was using a quart of oil every 300 -400 miles. The new seals cured it, 2000 miles and no oil use! The oil is staying cleaner now, not that black nasty stuff.
Let us know what the plugs look like and what your plans are. Everyone here is willing to help! Joe H.
