Quote:
Originally Posted by blykins
Wouldn't hurt to check that TDC is true TDC. Do you have a way to verify that? You can use a piston stop that screws into the spark plug hole.
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What's a little elastomeric slippage between friends?
I think what Blykins is eluding to is as harmonic balancers get old the 1/8" to 3/8" thick elastomeric band tends to get hard, crack and shrink. In addition, if the old engine's spewing
oil out the timing cover seal it tends to prematurely degrade that rubber ring too. That band separates the outer ring (where the timing marks are) from the inner hub (that bolts to the crankshaft). As it's age progresses it's more and more prone to slippage, meaning the outer ring is not in sync with the inner hub .. i.e. incorrect ignition timing if the marks are used for timing adjustments.
Then there's the cheap Chinese/Korean/Malaysian etc. balancers that a lot of our local auto chain stores sell... In performance applications they can slip right out of the box.
I've used a wooden pencil through a plug hole on numerous occasions with complete success, eraser end down. You can feel the rise and fall of the pencil. Depending on whose accomplishing, it can be pretty accurate on finding top TDC. Plug hole accessibility and a few other variables come into play also.