We explained that we wanted to complete a straight-up engine rebuild on our Grand Cherokee - we didn't want a high-performance gas guzzler. We wanted dependable, long-lasting parts able to withstand harsh driving conditions. What we received were a new roller cam and lifters, a high-volume oil pump, and all of the other parts, including pistons, timing chain and gears, and freeze plugs. All of these are high-end O.E. replacement parts. Clevite offers just about all engine components for domestic and foreign vehicles. Another thing that makes these components so attractive is the fact that none of them is made in China.
Bill took some time to point out some interesting features and considerations of particular importance to anyone wanting to boost performance or enhance durability during the rebuilding process.
For instance, the connecting rod bearings we received were Clevite's recently introduced TriArmor design, which incorporates an exclusive moly-graphite coating on top of a complete, otherwise-unmodified, Clevite 77 performance bearing. This coating is just 3/10,000 inch thick and comes out of Clevite's engine development program meeting the highest levels of performance demanded by NASCAR and other racing circuits. It is now offered for popular domestic and import engines. The specially coated bearings play an important role where the reciprocating action places the highest stresses on the bearings and crank journals, but also where main bearings' stresses tend to be particularly high.
This coating adds several benefits to Clevite's performance bearings. The exclusive moly-graphite coating is a super-slippery, state-of-the-art material that provides three key benefits. First, it offers protection to both the bearing and the crankshaft journal, especially during cold start-up when the protective film of oil has not fully developed. Second, with its greatly reduced coefficient of friction, this coating contributes to increased power and fuel efficiency. And finally, when this coating wears off after many miles of service, there's still a complete, unmodified, premium high-performance Clevite bearing underneath, ready to begin service all over again well into the new life of the rebuilt engine.
Machinists and engine builders will probably be asking, "But what about clearances to accommodate the added thickness of the coating?"
We were told that "with the coating just 3/10,000 inch thick on each bearing shell, the total reduction in assembled bearing diameter is 6/10,000 inch - 3/10,000 inch for each shell. At just over half a thousandth, this variance will often allow bearing clearances to stay within allowable tolerances."
However, for the engine builder who is obsessive about clearances, Clevite offers bearings for many engines in -0.0005 inch (half a thousandth extra clearance) so he can mix and match bearing shells to achieve the precise clearance he needs.
We also learned quite a bit more than we thought about piston rings. Compression rings were made of plain gray cast iron; however, engineers at Perfect Circle soon learned some pretty interesting things about the ring pack in automotive engines. One revelation was the fact that piston rings typically account for about half of all of the friction in an internal combustion engine, so rings have a major effect on the power and efficiency of an engine. Another was the fact that modern top rings often see temperatures close to 4,000 degrees F. Both these conditions indicate the need for a moly-coated top compression ring in a modern engine.