Help me out guys I'm a little rusty on this. I have the FSM and I'm setting timing on a 90 Convertible. I did this:

1) Warmed up engine and grounded single green connector to shock tower
2) Timing light RED to (+) battery post; Black to shock tower
3) Clamped light to lower front plug (L1) near engine. Yellow mark was off so loosened CAS and aligned so mark was on at idle. Tightened CAS 10mm bolt.
4) Took clamp off lower plug and put on front upper plug (T1).
---I expected to see red pulley mark with the light but it's still on yellow. Is this right?

 

Weird, checked again this morning with timing clamp at plug and the marks for L1 & T1 are on the pulley yellow mark. Same as yesterday. Move clamp to T1 at ignitor the mark changes from yellow to red mark like it should be. I guess it's all good?

 

You are only setting timing to the Leading mark anyways.
If you move the CAS to line the pulley up to the Leading mark on the pulley,Then moving it again for the Trailing you are Not accomplishing anything at all.
Think about it.
Set the leading and the Trailing spark takes care of itself.

You should try setting Timing on an FFE trigger..you get 180 degree off on Trailing..only when it wants to Show you a light..(like ghost reference..)

 

Yeah I get that, but it seems odd it stays on the yellow mark at L1 & T1 near the plugs, and reads correctly when taken near the ignitors.

 

Waste spark

...

 

The induction clamp I have read has something to do with why the timing gun reads sometimes Good and other times NOT.
You got to get the clamp "just so" in order to read the timing.
I just got the thing to read on one mark(whatever color it is supposed to be..I am on FFE Trigger now) and then locked the Cas and called it a day.
You shouldn't have to read individual plugs.