Chapter 8 It's a Grind

  Working on the block has been a parallel project with changes on the crankshaft.  The crankshaft started life as a forged steel Studebaker 289 unit.  It was stroked 5/8" to take the stroke from 3.625" to 4.250".  I had a lot of concerns about getting it to work for a Bonneville application centered around the close quarters and proximity of the camshaft.  More details on the camshaft is coming, but suffice it to say the lobes on the camshaft were very close to the bearing journals.  The cam used by Granatelli was very small in comparison as they had reduced the base circle to 3/4".  The roller cam I wanted to run and designed expressly for Bonneville use with a valve lift of 0.620".  I assumed the cam was reduced because of clearance issues with the stroker crank.

  Since the crankshaft was key to getting the displacement needed, I determined I needed to work on the crank and if it won't clear the giant roller cam I'd design another with reduced base circle.

  In balancing the crankshaft, extra weight was added to the end counterweights.  Otherwise, the crank was just like a standard 289 crank, just made longer in the rod journal placement.  The counterweights were the same shape and rod throws carried the normal contour out to the rod pins.

  Oil control is a big thing for me and I wanted to make this crankshaft enhance the oiling not make it worse.  A phenomenon known as windage occurs when oil from the bearings and cylinders is hit by the crankshaft dissapated into smaller droplets and pulled around the rod throws and counterweights by the rotation of the crankshaft.  Smokey Yunick did some experiments with windows in the oil pan to actually see windage in a running engine.  He reported seeing virtually all the oil in the pan making a larger and larger cloud with the appearance of a taffy pulling machine.  This creates a parasitic drain from the impacts.  Also, as more oil is entrained, less is available for engine lubrication and cooling.  Yes, cooling.  More on that later.  Eventually, with high enough RPM's virtually all the oil is tied up in the windage cloud and, in extreme cases, cause the oil pump intake to be uncovered and system oil pressure and flow goes to zero.  Bad combination.

  So, what can be done?  Various engine builders have done experiments in reshaping the counterweights and rod throws with good effect.  Arguably, the best method shapes the leading edge of the counterweights as a bullnose or rounded profile.  This reduces the impact of the crank slamming into oil draining down to the pan and encourages the oil to run across the surface to an edge where it can be channeled safely back to the oil pump.  The trailing edge is reshaped in a boattail with a sharp edge which sheds the oil in large drops to the main web or block wall, out of the way of the next oncoming rotation.

 The next step is a crankshaft scraper, a thin blade of Teflon which wipes the oil from the crank as it passes 90 degrees on the upward portion of rotation.  This, in conjunction with a well designed oil pan should go a long way to improving oil control.

  It takes a lot of grinding, shaping and smoothing using several tools to reach in and get to the  nooks and crannies.  The pictures show the roughing out of the shapes needed.  There is a lot of surfacing left to do.

  An added bonus is that the crankshaft is lightened during the knifedging greatly reducing bearing wear and crankshaft twist.  The smoothing of forging marks increases reliability as well.  There is another process yet to be done once the entire knifedging proceedure is done and the crankshaft is polished to a scratch free condition. The oil ports that run throught the crank need to be beveled removing the sharp edges and tapering them out to increase the time the bearings are in a place in rotation where oiling can take place.

In all, it's a lot of work.  Some folks pay someone else the $1000 it costs to farm this work out.  And we haven't verified other changes needed for clearance of this crankshaft.