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Cam timing...(again)


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Please be patient with me as I know there have been a few posts on this - but I am still slightly confused...



My question is if I am starting from scratch, how do I know which TDC number 1 is on - start of power stroke or start of inlet stroke - if the crank, cam  and timing wheels have no markings and have been removed and replaced.

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To time the cam shaft, you need to know where No.1 cylinder TDC is on the firing stroke. (at the start of the power stroke)


Any cylinder that is at TDC will be either on the firing stroke, or else at the end of the four stroke cycle (start of inlet), just about to start another cycle.

In that second case, both valves will be slightly open, but on the firing stroke they will be closed.

It's as simple as that.  

If both valves on No.1 are 'loose' - the rocker to valve stem clearance is still present - then it's on the firing stroke.


Does that help?


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If the cam is not connected the stroke is not yet set so No1 TDC is No1 TDC. With No1 at TDC then you set the cam so that the valves on no1 are closed and the valves on no4 are at the same lift (If I remember correctly)

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