Later slant 6 engines had a timing scope on the front of the block . A curved piece of brass with a tube in the middle to shine a timing light through. Does anyone have a extra timing mark like that?
Timing scope
- Thread starter Chuckman
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KitCarlson
Well-Known Member
I think a variable reluctance probe was inserted in the tube, it picks up a narrow notch in the pulley at TDC. A VR probe is a coil on a slug with a bias magnet, when the notch is encountered a pulse is generated. The pulse would be used to trigger scope, then the 6 cylinders could be viewed inline as pattern 3 per revolution. It is also a means to measure spark advance with scope, in conjuction with coil primary signals.
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Ya what he said. I new the tube was for a timing probe but until now I never knew how it worked. Thanks for the learning.
BillGrissom
Well-Known Member
From what Kit says, it sounds like you also would need a clamp-on current probe over several spark plug wires (3 at a time?). The special scope would be triggered by the crank sensor and you view the angular delay to each current pulse on the scope. Sounds useful only for shops doing it daily years ago. For us, the normal "flash timing lamp at crank" method seems easy enough, and is probably more accurate.
KitCarlson
Well-Known Member
Just look at coil primary voltage signal, clamp on #1 trigger shows 720 degree reference, VR probe shows TDC. On scope, without looking to light on pulley, it is possible to measure timing, and verify for each cylinder. With portable scope, do it on the run, with help.
I use similar method, because my timing reference is locked to base timing, actual timing measured from that point. Simple calculation by scale of degrees vs time at RPM. I hope that this is understood. It is the reason I do not build electronic advance for mechanical advance distributors. The ability to track and measure timing real time is lost, since no fixed reference back to crank.
I use similar method, because my timing reference is locked to base timing, actual timing measured from that point. Simple calculation by scale of degrees vs time at RPM. I hope that this is understood. It is the reason I do not build electronic advance for mechanical advance distributors. The ability to track and measure timing real time is lost, since no fixed reference back to crank.
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