Clearancing for pushrod clearance - Big Chief BBC
Bill Jones' Photo Gallery Page 13
When trying to get .970" lift on a BBC with 14º big chief heads and trying to use the large diameter pushrods----the bottom of the pushrods interfere with the edges of the lifter bore because of the offset pushrod seats in the roller lifters.
-This particular engine had stock size or the next size large cam bearings so it was limited to how large a lobe could be used---meaning that the basecircle diameter had to be reduced---which drops the roller lifter down inside the lifter bore---enough to be a problem with the offset of the pushrods
-The following seven photos show the notches that are needed near the top edge of the lifter bores and one photo shows a pushrod installed.
These first four photos show the BBC lifter bores and the offset pushrod seat of the roller lifters---where the edges of the lifter bores need to be notched for the large 1/2" x 7/16" tapered diameter pushrods being used in a 14º big chief engine with .970" valve lift.
-One photo shows just how deep the pushrod seat is below the top edge of the lifter bore.
-The pushrods used in this application have a long tapered end that helps immensely with the problem but still requires the bore edges to be notched.
These last five photos show the lifter bore notching tool closeup.