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Quote:
Originally Posted by SAJ
I had a similar problem. My fibre gear would knock quite loudly at idle. I tried various things to remedy this. After fitting a new aluminium gear and steel crank gear and drilling the timing cover for a thrust bolt I ended up with a rattle like piston slap at 3 different rev bands. It came and went as the engine travelled into and out of these rev ranges. After fitting a rubber harmonic balancer from Murray Horne in New Zealand the annoying rattle is gone, but there is still a rhythmic knock at idle. Replacing the timing pin with a polythene bolt removes the knock like magic when it contacts the rotating gear. Not a usable solution since the plastic bolt wears away quickly, but certain proof that it is the gear knocking, not something else. Tooth backlash was very tight when the gears were installed.
Engine was stripped to investigate what I thought was piston slap, but piston clearances were all 0.0035 to 0.004 as when the motor was assembled about 20000 miles ago.
I think harmonic vibrations of the crankshaft vibrate the two gears together causing the rattle and the harmonic damper damps the torsional winding up and unwinding of the crank, removing the rattling noise.
On the basis that "If a little bit is good then too much is better" I put a damper on our fibre geared, counterweighted crank Tudor engine and the almost subliminal noises that I could hear and my wife could not have gone on that engine too and it just sounds so much smoother at all speeds now.
I suspect that vibrations that occurred above 2400 engine rpm in a standard motor have been moved down into the running range by counterweighting the crankshaft in both my engines.
Others have the same experience. Look up my earlier posts in my profile for a lot of history and access to other members findings.
There has been a great deal written about noisy cam gears.
SAJ in NZ
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I agree there is a inherent load /unload condition of the cam/crank gear,I believe its the reason ford used a fiber gear,and a spring loaded plunger to counteract it. Stands to reason a harmonic balancer would help, dampen torsional impulse.Just installed a steel pulley to avoid the catastrophic potential for failure of the cast original,might go with a balancer in the future.