A If the rear is toed-out, and probably all of that is in the right-rear, as a result of the hit, then that could be a part of the problem. Bent rear-axle tubes are very hard to detect just by looking at them. There is also a possibility that the right-rear axle tube is bent in a way that increased the camber of that wheel.
Heating and cooling one side of the axle tube will shorten that same side. If excess camber is a problem, heating the bottom of the tube will correct the camber problem and heating the front of the axle tube will eliminate the toe-out. Heat the middle of the tube halfway between the hub and the rearend. Stay away from the gears and the wheel bearings. Drain the rearend lube first and replace it with fresh fluid after the tube has cooled.
Port FlowQ On page 52 of the January 2003 issue, there is a chart on "Mass Flow at Intake Valve." It shows a reduction of flow around peak lift. Please elaborate. Is this because of flow separation in the port? I would be interested in hearing if gains at peak lift are that beneficial, such as a 25 to 40hp gain.Gary CunninghamGrace City, ND
A As in the case with exhaust ports, intake port flow is non-linear. Simply stated, it begins with a brief period of back-flow (reversion), continues to a peak value, and then diminishes to a stop shortly after intake valve closing. Pressure excursions continue along the passage toward and away from the valve until the next event begins.
There is a point during the lift cycle (opening and closing) where the valve "resides" the longest. Depending primarily on rpm and rod/stroke ratio, this point (for the intake cycle) is around 65 percent of maximum net lift. In many instances, this coincides with a crank angle of about 65-70 degrees. Experience and data have shown that improvements in intake passage flow beyond this point yield less volumetric efficiency (torque) gains than at or near this "residence" period. So, if you had a choice between improving inlet flow at peak valve lift or within this 65-percent range, the latter is the clear choice.
Interestingly, you might think volumetric efficiency gains would be greater at this point on the opening side of the cycle than closing. This is typically not the case. Kinetic energy gains achieved before and near peak lift will continue into the 65-percent lift range past peak lift, thereby "skewing" the symmetry of an airflow curve superimposed on a lift curve. There is also a reason why inlet closing points (relative to piston position) are sensitive to an engine's overall volumetric efficiency capability.
Finally, the airflow reduction you noted around peak lift (per the January story) is caused by several factors that include combustion chamber wall effects, valve head influence, and the flow separation you suggested, along with other factors. As an interesting experiment you may want to conduct, try overlaying the traces of piston motion, intake track flow, and valve lift, all as a function of crankshaft angle. You're likely to discover some additional areas of interest leading to volumetric efficiency gains. Synchronization of valves' motion-to-piston motion can be a revealing aspect of part selection.Jim McFarlandAutotronicsAustin, TX
Ackermann ApplicationQ I have read numerous articles on the Ackermann principle. I understand the theory and principles presented, but I am having a problem applying this to a stock frame/spindle setup. The basic setup is a Chevy metric chassis. The drag link and tie rods are in front of the crossmember and the steering arms are forward of the pivot point. Correct Ackermann steering geometry should cause the inside (left) wheel to toe-out to a greater angle than the right wheel during a left turn. I understand that this toe-out is not to be confused with static toe-out that is set by adjustment of the tie-rod length. If proper static toe-out exists, how does one achieve Ackermann, the difference in turn radius between the front wheels, with a stock spindle and stock front-end steering linkage?Bob TrykaRochester, NY