Doesn’t matter. I have a simple light that has no tachometer on the light and it works great. I believe your 4-6-8 setting is to get the tachometer calibrated correctly on lights with digital tachs.
I have a Sealy. It puts out a pulse whenever it detects a peak on the injector tube. The pulse is picked up on the light which gives a flash. It’s that simple.
I forgot my numbers but I recall using the advance shown in these threads. Lemme look it up in my notes. 19 degrees. Did the same on my 300sd and 300d. They run great.
I got to use my dad’s old craftsman timing light. He splurged and got the “Sears Best” model in 1982. I grabbed it out our garage in Altadena back in 2021. It’s one of the few tools I saved from the big fire because it lives in my garage in Irvine. It’s cool that it got a second life as a diesel timer. I thought it was old trash till I realized it could be used with the Sealy. Really well made when Sears was good stuff.
For the curious here is the board in the sealy. The piezo signal is amplified and sampled by an Atmel microcontroller. I believe some adaptive filtering is done to get rid of the false triggers. Then a single pulse is generated and this is sent to another amplifier that makes a small current flow in the loop of wire the clip attaches to. It’s pretty simple but I must say it’s well worth the $150 I paid for it. Makes timing a breeze with no guesswork.
Yikes. My memory is going. Here is my post after I dialed in my SD. Apparently the idle advance is quite different than the advance at 1000 rpm.
https://www.peachparts.com/shopforum/4205139-post34.html