View Full Version : rod stress, h vs I

04-11-02, 01:21 PM
look this over








NOTICE that the connecting rods high stress areas are areas the rod is under TENSION NOT COMPRESSION , most people fail to realize rods tend to fail on the exhaust stroke where there is less opposeing force slowing the piston as it nears tdc, rods commonly fail from being streached not compressed, and the points the tend to fail at are the rod bolts, or just under the small end holding the piston pin and the large end where the rod changes size to go around the crank journal, now it mostly depends on the QUALITY of materials used, the care used in manufactureing and overall design but (H) type rods normally place more steel in these stressed areas for the total weight of the rod than (I) type rods so thats why you see those type rods in the higher stressed engines but like I said a QUALITY rod of EITHER DESIGN works fine, and its the rod BOLTS that normally fail first,or the area just under the piston pin from stress cracks when you pull an engine apart and find the rod broken in most cases a rod bolt failed first and as the crank started slapping the loose rod against the block it bent and broke the rod, its not normal to find a big end of the rod still on the crank with good bearings and bolts yet broken in the center area , look again at the stress analysis color photos ans see what IM talking about!