Lock Down Musings

[Bob Culver]

Another subject for another day. For low comp small bore engines the upward force at end of exh stroke exceeds at modest rpm the net downward force on the full throttle firing stroke. At high revs, on the power stroke the upwrd thrust is so great the piston does not push down so much as not push up! On the overrun the two middle pistons both push up and down with full force together bending the crank.  Hence at 60 mph it is prudent to coast your Seven down the motorway gradients (assuming you have found a suitable truck to slipsteam).