[cyberpigue]

Visualize a bicycle chain. When you put pressure on the pedals the chain sags between the front (drive) and rear (driven) sprockets at the bottom since the top is being pulled tight by the pressure on the pedals - gravity pulls the slack in the chain down and keeps it from bunching up at the rear.

A timing chain does the same thing except the drive sprocket is below the driven sprocket where gravity doesn't help with the slack as much. To deal with the slack there is a tensioner on the "loose" side to keep the chain tight and not bunching up. As the chain stretches over time and the spring on the tensioner weakens over time, the slack in the chain begins to become greater and the chain begins to fluxuate like a wave. The high points on the wave can hit the timing case cover, or move the tensioner in and out causing the noise.

Just as in the bike, if the chain gets too loose, it can fall off or jump a tooth on the sprocket. That's big trouble in an engine because now your valve timing is not aligned with your crank timing. Besides running poorly, if the valves don't have sufficient recess in the head, an open valve may make contact with the piston at top dead center - blown engine.

By simply replacing the chain set (chain and gears) and tensioner, engine no breakie...

 

[cyberpigue]

It's impossible to tell you whether this is the noise problem with your engine. Even if it was or wasn't common, yours might be something else. Have someone you trust listen to it.

Generally, lower end noises that are rod or main bearing related are accompanied by lower oil pressure since the space required between bearing surfaces to result in a knock are also great enough to allow oil to quickly evaxuate from the journals (tubes inside the crank and block that the oil flows through) causing lower oil pressure.

If you are burning oil, that is generally caused by oil entering the combustion chamber at either the piston rings or at the valve seals. Possible at a head gasket, but much less typical and almost always accompanied by water which causes a lot of steam to pump out of the exhaust.

Oil smoke is a bluish white and doesn't dissipate quickly. Steam is a clearer white and goes away quickly once in the air (plus it smells like antifreeze). Black smoke is a indication of the fuel mixture being too rich - maybe a stuck choke, misadjusted carb float, or bad emission sensor on computer controlled engines.

There are two "most important" factors in your engine lasting... clean oil and good air filtration. Buy the best oil you can afford and keep it changed. Buy the best (not neatest/coolest) air filter you can afford and keep it changed.

Additionally, look for problems where grit can enter your engine. The best air filter in the world is of little use if there is an air leak between the filter and the engine. Great oil with a leaking valve cover sucking in who knows what gets dirt fast. The dirt is like comet scrubbing away your engine metal.

My old Wagoneer has a couple of hundred thousand miles on it. When I got it with 127K miles on it the engine had been rebuilt at 90,000 miles. It already smoked and leaked and wasn't very healthy. I slowly replaced gaskets and seals and changed the oil several times in a short period and it has lasted me six years without a rebuild. Even a worn out engine can be made to last if it gets good loving... and stays away from grit.

 

[cyberpigue]

I just got it back from Chrysler

Did you ask them to replace the timing chain or did you ask them to fix the knock? If they misdiagnosed the work, you need to speak with the service manager. Be nice but firm. If that doesn't get you anywhere, speak with the general manager, then owner. At the very least the work should be discounted. You did get something of value, but the wrong something of value.

 

[cyberpigue]

Did the dealer you bought it from pay for the repair?

 

[cyberpigue]

they paid all but $225. I wouldn't call it a repair I just went out and listed to it again and it's just as bad. Now I'm thinking or maybe I'm just hoping its the rocker/lifters. is there any adjustment on the rockers? Or how do you fix them if there noisy?

http://www.wranglerforum.com/showpost.php?p=57898&postcount=6