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bazzbazz

Tdc

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A friend brought up an interesting discussion.

 

When using the dial gauge to find TDC, the gauge will rise till it stops, then there is a small period of "dead spot"

where the crank continues but the piston is static, then starts to drop.

 

When setting TDC for a cam belt change, where is the official correct spot?

 

A/ When it stops rising

B/ The middle of the "dead spot"

C/ The moment it starts to drop

 

Baz

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TDC is the centre of the "dwell" when the piston is at the highest point.

 

The dwell is created by the lubrication gap between the big and little end shells and can be used to diagnose excessive wear within the engine.

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Thanks Smaky, that's the line I have been arguing, but it is interesting to know you can use the dwell to diagnose wear. Can you elaborate s little more on that with twinspark & JTS engines?

 

Baz

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I assumed that, but would you know what the min & max dwell should be as in relation to wear on the bearings?

 

Baz

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Different engines start with different gaps, it's hard to say but if you're getting more than 5 degrees of dwell on the TDC then it's time to think about new shells.

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