Jeep Engines - Oljeep

150 MOPAR PERFORMANCE PARTSWe began this discussion trying to find out how to tell if acap had been reversed. We now know how to locate the capand how to install the connecting rod assembly in theengine. These two items are closely related because themethod of determining main cap orientation and the key toinstalling connecting rods are the same. It is important toknow both because once the connecting rod and piston areassembled, the cap still has to be removed one more time toget the connecting rod on to the crankshaft. One morechance to reverse the cap or the connecting rod. Our maincheck on the assembly at this point is usually the valvenotch on the top of the piston. However, it is also a goodidea to double check the chamfer-crankshaft relationshipafter the connecting rod/piston installation to verify that acap didn’t get reversed in the last step.Connecting Rod Bolt ProtectorsIn every engine assembly or build-up, the piston andconnecting rod assembly must be installed into the blockand on to the crankshaft. During this phase of engine buildup,the connecting rod bolts have to be protected. This isbecause when the connecting rod cap is removed to allowfor the installation of the connecting rod and pistonassembly and the bearing shells, the connecting rod boltspressed into the connecting rod are left sticking outunprotected. Aluminum connecting rods have theconnecting rod bolts threaded into the connecting rod beamand are, therefore, one of the few exceptions to thiscondition. In any case, the bolts that stick out must beprotected during installation.To protect the bolts, cover the connecting rod bolt threads.There are several choices for protectors. The “Pros” tend touse threaded brass rods. Another option is simply a piece ofrubber fuel line. Our favorite is neoprene (clear plastic)line. Lengths are somewhat optional, but should be at least9” - 12” long for the top bolt. The second piece, for thebottom bolt, could be as short as 3“ - 4” long, but 9” - 12”long is recommended,The main reason the threads need to be covered is to protectthe crankshaft journal during piston-connecting rodinstallation. If you don’t use protectors, it’s very easy toscratch the connecting rod journal with the end or threadsof the connecting rod bolt. Crankshafts are much moreexpensive to repair or replace than connecting rod bolts.A secondary function of connecting rod bolt protectors is toguide the connecting rod over the crankshaft journal duringinstallation. This is only true if you use at least one longprotector. If you use short ones (or none at all), then theconnecting rod can easily end up on the wrong side of thejournal, which can result in other damage.The proper procedure for installing the connecting rod andpiston assembly begins with the crankshaft’s rod throw atthe bottom of its travel, or BDC (Bottom Dead Center).Generally, the cylinder that you are working on should betipped on its side. This makes slipping the connecting rod,piston and ring assembly into the block easier. In thisconfiguration, the long protector should go over the top ofthe connecting rod journal. Before you make an error,remember that the piston MUST be installed into the blockin its proper orientation for pin offset, valve notches, etc. Sothe first task is to determine this orientation BEFORE youinstall the connecting rod bolt protectors. Now put the longprotector on the top bolt as installed. Somewhat confused?Now you can see why using two long protectors might beeasier to work with and is the recommended choice.As soon as the piston and connecting rod assembly is seatedagainst the crankshaft journal, the connecting rod boltprotectors are removed.ALUMINUM CONNECTING RODSNote: Aluminum connecting rods should be used ONLY inconjunction with lightweight pistons.Aluminum connecting rods are a race-only piece. Althoughmost standard production connecting rods are designed forpressed-pins, most race pistons are designed for fullfloating pins. When building a race engine, the pistonswould generally be replaced before the connecting rods.For an all-out race engine there are advantages to the fullfloating pin. (Be sure to check pin clearance in theconnecting rod upon assembly.)If y~ou broke a steel connecting rod, you’d probably buy anew one, rebuild it and put everything back together.Aluminum connecting rods aren’t quite that easy. (By“breaking” we mean a partial failure like a scuffed big end,overheated, bent or nicked from handling. If the connectingrod breaks in two, there won’t be much left to “put backtogether.”) With aluminum connecting rods, if you drop oneand nick it, you can replace it with a new one. However, ifafter several runs you scuff it, overheat it, bend it, etc., youdon’t want to just replace it. Your best bet is either toreplace all six connecting rods or to send the five goodpiecl-s back to the manufacturer and have them “rebuilt”and matched to the sixth. We strongly recommend keepingany instruction sheet or other manufacturer information thatmight come with your specific set of connecting rods tohelp you contact the manufacturer at a future date.The main advantage of aluminum connecting rods is theirlighter weight. However, they do require some specialconsiderations. These special considerations are primarilyclearances, which may be slightly different from steelconnecting rod numbers. These differences can beimportant. Be sure to check with the manufacturer forcorrect specifications.l- - T ’ l