Ignition Timing - using timing light questions for a noob

[ramonesfreak]

I could use some help making sure I do this right. My confusion mostly has to do with the use of the digital timing light (Innova 5568a). Ive never set timing before or used any timing light...so this is all a foreign language to me

The car is a 1983 911SC. I will be setting per Bentley to 5 degrees +/- 2 BTDC at 950 RPM and 21 degrees +/- 3 degrees at 6000

1) Do I set the light to 05 when setting the idle timing? I assume yes

2) I assume once I set the light to 05, I then point the light at the 5 BTDC mark on the pully and line it up via turning the distributor. Correct?

3) When setting timing to 21 degree @ 6000, do I set the light to 21 degrees? Again, I assume yes.

4) When setting timing to 21 degrees....what mark on the pully am I looking at? Do I need to measure to a spot on the pully that is 21 degrees and mark it with paint and then line that mark up....or is there a mark on the pully from the factory that I have never noticed or do I use Z1 or what? This is the biggest mystery to me.

5) Last (I think)...on the light do I set the degrees using the "advance" function? I think the term "advance" is confusing me because when I think before top dead center I think if back not forward. To me advance = forward...confusing

Thanks in advance

[RSTarga]

If you use the advance on the light use the z1 on the pulley.
If you set the light at 0 you need to locate 5degrees and 21 degrees on the pulley. They should have indents on the pulley if those are indeed the specifications

[ramonesfreak]

I’ve never seen or heard anyone reference the 21 degree mark on the pulley. It’s not noted in Wayne’s book, Bentley or Haynes that I can find which is why I’m confused about that. I’m probably wrong but that’s why I asked question #4.

I know where the other marks are

Why would I use z1? If I were using an old style non digital light, I would be looking at the 5 BTDC mark wouldnt I? Doesn’t make sense to me

[Nditiz1]

Easiest way is as was said, set your the timing you want to achieve on the gun, 5 degrees, ok. Turn the distro until you get z1 to line up with the fan shroud mark. I want 21 at 6000, set gun to 21 - hold rpm at 6k move distro until you see z1 on the shroud. By doing so this may change your idle timing, which who cares its idle. Set your 6000 and let the idle fall where it does.

[ramonesfreak]

So if I’m setting the degrees on the gun, then I no longer care about the 5 BTDC mark and the fact that I can’t locate a 21 degree mark on the pully? Ok that sounds straight forward.

[Nditiz1]

Exactly. You only care about z1, which is why those types of guns are nice.

[ramonesfreak]

On an 83 can anyone tell me what turning the distributor CW and CCW does…advance vs retard…I don’t want to mess around too long at 6000 rpm with my hand reaching over to the throttle linkage and light gun in the other hand.

Not sure my car has even seen 6000 ever

[pampadori]

you'll notice that full advance is probably all in by 3500 or 4000 RPM. No need revving to 6,000 if there is no advance left in the distributer mechanism.

I think most folks run more than 21* full advance on the 3.0 CIS motor. But that number might be with a vacuum hose unhooked or something. If Bentley says so....

[ramonesfreak]

I’ve read that as well

[RSTarga]

Normally I set the idle advance and then quickly rev it to 6k to double check, my distributor curve spec states there is still advance left until 6k.
Get the proper specs for your car.