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Old July 24th, 2014, 09:26 PM   #1
Outlaw Bill
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Join Date: Dec 2001
Location: Canton, Michigan
Age: 48
Posts: 11,064
Default GET IN LINE! - Are your sprockets lined up?

The basic engine building procedure than seems to be overlooked nowadays is making sure that the upper and lower timing chain sprockets are in line with each other. With incorrect alignment, the stresses created can easily lead to premature timing chain failure (and we all know the mess that creates), and if the misalignment is pulling the cam forward, the lifters can contact the adjacent cam lobes and journals, creating an engine full of debris and again, failure.

With a proliferation of aftermarket blocks and crankshafts, along with many different choices of timing sets (each having numerous thrust bearings and shim options), itís difficult to assume that all will be fine. Even standard blocks may have had their cam thrust faces machined for one reason or another, and if that info is not passed on, there's another opportunity for disaster.

To confirm proper alignment, install the crank sprocket (apply mild heat via submersing in hot water if necessary to ease installation), making certain that it is up against the register on the crank. Then install the upper sprocket onto the camshaft, including any thrust bearings, thrust shims, retaining plates, etc. Then install the camshaft (without timing chain) into the engine, torquing all fasteners as required. You may also want to install the front balancer at this time, to insure that the crank sprocket is being properly positioned.

Place a straightedge against the front edge of the sprockets and inspect to confirm that straightedge contact is continuous on the sprockets. If the cam sprocket is too far back, a thrust shim may be able to be added behind it to obtain proper alignment (you'll need to make sure that the lifters and lobes are still properly aligned if you use this option). If this is not possible, a step on the rear of the crank sprocket may have to be machined to allow it to slide further back on the crankshaft.

If the cam sprocket is too far forward, the thrust surface on the rear of the cam sprocket may be machined (again check lifter to lobe alignment), the thrust face of the block may have to be machined (yes, engine disassembly time again), or a shim placed behind the crank sprocket to achieve alignment.

These are numerous possibilities to correct misalignment, depending on the engine type and optional timing components that may be available. The main thing is to check this as early as possible in the engine building process, allowing you the time to exercise different choices to correct any difficulties.

Also, check to be certain you have sufficient clearance between the chain and the block casting, and the chain to the timing cover. With many of today's wider chains, space may be at a premium.

Checking these factors will help allow your engine to have a good, long life. This is cheap insurance to protect your investment.
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