Also the crank journals & therefore big end rod bearing journals are all the same diameter (153, 194, 230, 250, 283) since the 283 was still using a small journal crank. Intake & exhaust valves are dimensionally the same with 1.72" intake & 1.50" exhaust, although the 283 had aluminized faces on the valves. The 153 four & the sixes had an 8.5:1 compression while the 283 used a 9.25:1 compression. Combustion chamber volume per cylinder at TDC was 5.37 cubic inches for the fours & sixes, 4.47 cubic inches for the 283.