Tuning a 79 ignition distributor

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29 Jul 2016 19:16 #19224 by joejabq
I'm pretty sure that I need my ignition distributor serviced to set the advance curve.
I can't set the timing to the specs. I don't get a steady consistent fire at 3000 rpm,, it's too retarded at idle, and seems to really advance once the vacuum hose is put on.
Does anyone have a recommendation for someone to service and set the advance curve for the distributors?

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02 Aug 2016 00:10 #19227 by Kiln_Red
Here is a helpful link.

The fact that your timing is too erratic to get a dependable reading suggests to me that there are vacuum leaks to sort.

IIRC then the vacuum advance should change the advance roughly 8° at 3000RPM, so 23° BTDC is what you're looking for without vac advance.
The following user(s) said Thank You: joejabq

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14 Aug 2016 09:13 #19250 by joejabq
Thanks! I'll look for a vacuum leak(s).

I found that link as well. It's a little confusing because the numbered steps are out of order, but just to make sure that I'm interpreting it right, could you verify for me...
-With vacuum tube off the distributor, at 3000 rpm, 31 deg BTDC
-Still with vacuum off, at 5000 rpm, 35-38 deg
Am I getting it right?
this is what I tried to set timing to...
What I'm seeing is that I get an oscillation at 3000 ( I set as close to 31 as I can), and then even a small increase in RPMS takes it way more than 40 degs
Would this suggest that (1) there's probably a vacuum leak, and (2) the distributor needs to get re-tuned?
Is this unusual to see with older 928's?
If the distributor needs work, who would re-tune 928 distributors advance curves?
Thanks!!!

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