This could be one of the most meaningless post to show up on this forum. Also will mean nothing to people that have not repaired 70 series and later CASE built 6 cly. engines. While assembling a 1070 engine yesterday the same question came to mind as always does while working on them. My guess is others have had the same question occasionally. The nuts securing the intake manifold are those oversize 3/8. We know useing those or the standard size makes no difference. My guess is because they are not the common size and slightly larger cost more. These companys go through great length to save every penny they can, so why in the world would they use those there and no place else on the entire tractor. See I told you it was a meaningless subject, LOL, Rod.