This topic contains 1 reply, has 2 voices, and was last updated by 
Richard Kirshy 2 years, 8 months ago.
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I have a timing & tdc question, all I get online deals with distributor caps. My S10 has 235,000 miles, I replaced the sprockets, chain & tensioner and aligned them with the tabs on the tensioner. Now I need to find tdc. I watched your video on how to do that with a psi/vacuum gauge. My question is do I need to retime after twisting the drive shaft back and forth to find tdc?? And does it matter if timing is 1 degree off?
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Timing is both mechanical and electrical.
All mechanical timing is set ( as far as I know) with #1 cylinder @ TDC.
This can be done with a pressure gauge or by removing the #1 spark plug and inserting a long screw driver or something similar down the spark plug hole.
Barring the engine over until your into the compression stroke of the #1 cylinder and watch for the tool or pressure gauge to reach its highest point.
MAKE SURE your on the compression stroke or the mechanical timing will be 180 degrees out.
That will be TDC.
Now go and check all the alignment marks.
Once everything is aligned and tighten in place it should not change.And does it matter if timing is 1 degree off?
There is usually a range in which the engine runs sometimes + / – a few degrees each engine varies so one may run well at say 8 degrees BTDC where another may run well at 10 degrees or perhaps 6 degrees.
Hence the word tuning.
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