4AG AND 7AFE CRANK SHAFT INFO, FROM CLUB4AG.COM Options

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http://club4ag.com/faq%20and%20tech_pages/...20Analysis.html


7A Crank:




This is a photo of a 7A crankshaft. Its stroke is 85.5 mm and weights 32.5 Lbs. Though it is forged vanadium steel and fully counter balanced, there are features about this crank that one should be aware of that make it less than ideal for heavy duty competition. Please note that this crankshaft can not fit into a 4A block. The crankshaft pin diameter is 48.0mm. The counter weight outside diameter is 69.0mm, and the counter weight “arm” thickness is16.75mm. This makes the journal and counter weights too large and the resulting connecting rod angle too great for one to fit it in a 4A-G block.









This picture of the 7A crankshaft shows the location of the oil passages. The holes/passages are all on the same plane. This makes it easier for manufacturing since the crank does not have to be rotated or the drilling machines indexed 90 degrees. Also notice this design does not require plugging. However the placement of the oil holes and passages takes away needed material from a critical area and compromises the cranks ability to combat the larges forces being applied in shear on the journals and mains.



This photo shows the unique fillet rolling on both the crank main and rod journal fillets on the 7A crank. This practice is to increase strength at the area that is subjected to the highest stresses. Also notice the off center oil hole of the main bearing journal. This position will not allow a full 360 degree supply of oil to the rod journal. And it is positioned in a less than ideal area to take advantage of the maximum width and maximum strength of the journal.



This photo of the 7A crankshaft shows the less expensive manufacturing process of only drilling and tapping six holes for the flywheel. Eight is the minimum needed for heavy duty usage. However there is ample room to add a couple of shear pins.

This post has been edited by presure2: Sep 8, 2005 - 12:36 PM