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sean View Drop Down
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    Posted: 29 July 2007 at 6:34am
I believe I have "rooted out" when the the engine block casting changed.

GROUP 10-02 CYLINDER BLOCK & HEAD, shows 2 different assemblies:
  • #640163 - Block & Bearing, cylinder, assembly ('45 parts list)
  • #641145 - Block & Bearing, cylinder, assembly chain or gear drive ('47+ parts lists)
The earlier part would be the 638632 casting, while the later would be the 641087 casting.  The parts lists do not indicate when the change occurred.

Besides the casting number, they can be differentiated by the shape of the upper cylinder casting.

The 638632 casting, right side:


The 641087 casting, right side:


Notice the areas in front of and behind the lower row of freeze-plugs.

The 638632 casting is radiused to the approximate contour of the cylinders:


The 641087 casting remains rectangular right down to where it meets the crankcase:


They are also different inside the valve & tappet cover, but not visible on an assembled engine.

The 638632 casting - holes for the valve cover bolts are flush to the back wall:


The 641087 casting - holes for the valve cover bolts have a cast boss:


The '47+ parts lists, Group 10-10 - VALVE SPRING COVER, show 2 different length bolts:
  • #632158 - BOLT, 5/16"-18 x 4 1/8" (front) - up to eng. #89011
  • #645093 - BOLT, 5/16"-18 x 3 11/16" (long) - after eng. #89011
  • #639052 - BOLT, 5/16"-18 x 3 1/16" (rear) - up to eng. #89011
  • #645094 - BOLT, 5/16"-18 x 2 9/16" (short) - after eng. #89011
Following that trail of bread crumbs, I would conclude that the casting number changed at eng. # 89011.  The shorter bolts only work w/the "bossed" block casting, while the longer work only w/the "flush" block casting.

If correct, that would imply that there was a 3rd., undocumented, Willys part number for "Engine Block & Bearing assembly":
  • part #640163 - 638632 casting, chain drive only - up to eng. 44417
  • part #64???? - 638632 casting, machined for gear drive parts - after eng. 44417 up to 89011
  • part #641145 - 641087 casting, machined for gear drive parts - after eng. 89011
This intermediate part number came & went in between publications.  It didn't exist at the time the '45 list was published, and had been superceded and purged by the time the '47 list was published.



Edited by sean - 30 July 2007 at 3:28am
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