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  #1  
Old 09-19-2011, 08:43 PM
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Join Date: May 2010
Posts: 71
Setting up ignition timing on M117.984

I recondition distributor on my car and reinstalling it, one problem is that I have no idea how to tune the ignition timing. Is there a step by step guide on how to do it? I got all the tools and data just don't know the procedure.

For my car the setting should be:

Adjusting Value of Firing Point with vacuum at idle: 5 degrees TDC
Test values ignition adjustment with vacuum @ 1500rpm: 11-15 degrees
Test values ignition adjustment with vacuum @ 3000rpm: 18-22 degrees
Vacuum adjustment after retard at idle: 10-14 degrees
Installation value of ignition distributor at starting speed without vacuum: 7 degrees before TDC

Can anyone point out to a DIY that explains how to apply that data? I searched on this forum and googled and surprisingly found nothing.
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  #2  
Old 09-21-2011, 04:58 PM
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Location: Tucson, AZ
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Quote:
Originally Posted by SickFinga View Post

Adjusting Value of Firing Point with vacuum at idle: 5 degrees TDC
Test values ignition adjustment with vacuum @ 1500rpm: 11-15 degrees
Test values ignition adjustment with vacuum @ 3000rpm: 18-22 degrees
Vacuum adjustment after retard at idle: 10-14 degrees
Installation value of ignition distributor at starting speed without vacuum: 7 degrees before TDC

Why anyone would set it I don't know but, at cranking speed, the #1 plug should pulse at 7 degrees before TDC.

At idle, warmed up, vacuum line connected, you should be reading at about 5 degrees BTDC but it might drop to as low as 5 degrees ATDC depending on the emissions requirements for your car.

No vacuum, at idle, engine warmed up should be about 10-14 degrees BTDC.

At 1500 RPMs, vacuum connected, 11-15 degrees BTDC.
At 3000 RPMs, vacuum connected, about 20 degrees BTDC.

Easiest way is to disconnect the vaccum, set at 14 degrees BTDC at idle, rev the engine to 3000 RPMs and set the timing to about 30 degrees BTDC. You might have to give a little on either the 3000 or idle to get the best match-ups between the two settings. You, know, lower the timing at idle a shade to keep from over advancing at 3000 RPM's or vice-versa. Try to get the best even split.
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Old 09-21-2011, 08:08 PM
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Join Date: May 2010
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This is what I gathered so far on how to set it. Please tell me where I'm wrong.


1. Warm up the engine.
2. Remove the vacuum line from the distributor.
3. Point the stroboscope to the crankshaft and adjust the distributor until I get 14 degrees BTDC
4. Hook up the vacuum line back
5. Point the stroboscope to the crankshaft and adjust the distributor until I get 20 degrees BTDC

Is that the correct procedure?
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  #4  
Old 09-21-2011, 08:22 PM
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Location: Tucson, AZ
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Important step you left out in #5.

Rev the engine to 3000 RPM's and THEN check the maximum advance timing.
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  #5  
Old 09-21-2011, 09:17 PM
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Location: Stockton California
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What I read is to set the initial setting to seven degrees before top dead center with all vacuum hoses disconnected from the distributor and plugged. All the other specs are controlled within the distributor vacuum advance and retard diaphrams and mechanical advance weights inside the distributor. Once the base setting is done, you need to verify with the timing (strobe) light that the timing reacts to RPM increases as listed in your specs. If it doesn't you have issues with the vacuum advance diaphram leaking or the mechanical weights sticking or overextending because of wear.
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  #6  
Old 09-24-2011, 09:41 PM
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OK, something is wrong. When I rev the engine my timing is actually retarding instead of advancing. Any ideas why?
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