Setting timing on and '82SC after rebuild
 

Although I rebuilt the distributor as part of my overall rebuild, I recently discovered that the vacuum advance on my distributor was seized. When I rebuilt it the first time, I didn't use the excellent guide by Gunter and did not fully understand how the vacuum advance worked. I did not realize that the magnetic pulse generator assy needed to pivot on itself in response to the vacuum diaphragm. After trying to set the timing and not seeing any change in timing with vacuum applied, I took it apart again and unseized it.

So, I have a more functional distributor now but I'm still confused as to how to set the timing. The Bentley manual says to leave the vacuum hose (hose, not hoses) disconnected while setting the timing. Does this mean both the retard and advance hoses are disconnected, or just the advance? If I take them both off and set the timing to 5deg BTDC, as soon as I put the retard vacuum hose on, the timing is retarded ~5 deg at idle.

Maybe its my crappy HF timing light, but I can't seem to get a good enough reading when I blip the throttle up to 5-6000 RPM. Again, Bentley says that the hose should be disconnected and timing should read ~21deg BTDC at 6000RPM. With the vacuum connected, this should read 21deg + the max vacuum advance (~5deg?), correct?

Thanks.

Geoff


Now that may vacuum advance is working

Sounds like you are doing it correctly. I can't verify the timing specs b/c I don't have the Bentley in front of me.

After reconnecting the retard line you will likely have to bump up idle speed (due to pulling timing back by 5 degrees). I prefer to leave my retard line disconnected and plugged. It is only there for emissions from what I understand.

Maybe you can get someone to blip it while you keep an eye on the timing light.

Curious ... how many miles on the rebuild?

Both hoses are disconnected
You should have the major advance with the distributor @ 4000
The retard side is for emissions only so you can just plug that if you like and set idle where you like it
Idle is slowed with retarding the dist.
The 5 degrees advance at idle allows you to 28degrees advance with everything working.
Make sure your taps at the throttle body are open and not coked closed.
Bruce

Ok, thanks - I think I have it.

It is fresh from the rebuild (<100 mi).

In addition to setting the timing, I'm trying to figure out the idle mixture as well...

Geoff

If you have an inexpensive DIY timing light, it'll jump all around high rpms. You need a serious technician's light to do that. Been there, ultimately had to take my '83 SC to a shop to get the high-speed timing set right.

I think I got it. I adjusted it to the 5deg advanced with the vacuum lines off. With both vacuum lines on and the timing light set to 28deg adv, it lined up at high RPM's. My crappy HF timing light is a bit jumpy, but it settles down at high RPM's when the advance stabilizes.

I think I'll take it somewhere to have it checked tho as I may need to find a gas analyzer to get the idle mixture right, too.

Geoff

Good idea. I did the same thing just to be 100% sure that everything was sorted before getting too far into the break in.

Have fun!