How to Check Distributor Advance/Retard

[arbita1]

Can someone confirm if this is the correct procedure to check centrifigal advance, vacuum advance, and vacuum retard for an 83SC. Thanks.

[moneymanager]

It ought to be ok; you're looking at the factory's guidance.

[James Brown]

Why would you question this? you have a better idea?

[arbita1]

Originally Posted by moneymanager

It ought to be ok; you're looking at the factory's guidance.

Originally Posted by James Brown

Why would you question this? you have a better idea?

I probably should have added...

The manual I have shows this procedure for testing a 1980 SC. There is then another procedure for the 1981 and on SC. See below.



This one has a different test procedure for the centrifigal advance and doesn't address the vacuum retard.

Which one is right? Or does anyone have the right one for an 83?

[Steve@Rennsport]

Matt,

The factory procedures provide a quick check to see if things are working properly and the ONLY other way would be to use a distributor machine to do a thorough runup.

[arbita1]

I want to do the factory procedure. I just wasn't sure which was the correct one. After a bit more research, I think I've figured it out.

The top one is the correct one for the USA version 80-83 (with vacuum retard).
The bottom one is for the 81 (maybe 80 as well) - 83 Euro version (without the vacuum retard).

[Walter_Middie]

My resource shows different settings for a 1980 and 1981 through 1983 with the following:

1980 3.0 liter 911SC (North America)
Vacuum line disconnected
5 deg BTDC at 900 to 1000 RPM
15 to 20 deg BTDC at 3000 RPM
19 to 25 deg BTDC at 6000 RPM


1981 - 1983 3.0 liter 911SC (North America)
Vacuum line disconnected
3 to 5 deg BTDC at 850 to 950 RPM
25 deg BTDC at 4000 RPM

My resource doesn't say anything about the vacuum retard hose, nor does it talk about a maximum setting (25 deg) at 6,000 RPM.

I'd say that the factory procedure for 1981 should be followed until you are more familiar with setting the timing for your car, as my resource shows the timing is the same for all 1981 - 1983.

[arbita1]

Originally Posted by Walter_Middie

My resource shows different settings for a 1980 and 1981 through 1983 with the following:

1980 3.0 liter 911SC (North America)
Vacuum line disconnected
5 deg BTDC at 900 to 1000 RPM
15 to 20 deg BTDC at 3000 RPM
19 to 25 deg BTDC at 6000 RPM


1981 - 1983 3.0 liter 911SC (North America)
Vacuum line disconnected
3 to 5 deg BTDC at 850 to 950 RPM
25 deg BTDC at 4000 RPM

My resource doesn't say anything about the vacuum retard hose, nor does it talk about a maximum setting (25 deg) at 6,000 RPM.

I'd say that the factory procedure for 1981 should be followed until you are more familiar with setting the timing for your car, as my resource shows the timing is the same for all 1981 - 1983.

I'm just looking at Bentley and they lump 80 - 83 as all the same specs:

3 to 7 deg BTDC at 950 RPM
18 to 24 deg BTDC at 6,000 RPM

This would be consistent with the 80 version test procedure above (which I think is the correct one for USA cars).

[James Brown]

This is one of the great reasons to have as many repair manuals as possible. Sometimes one is wrong. Or just not as complete as others. Even the factory manuals have errors.

[VFR750]

arbita1,

Thanks for posting this page. I've wondered how to check the vacuum advance and retard functions. I posted a few days ago wondering why the timing went 5-10 ATDC with the too lines attached. Now I know it is correct!

Plus I can check the functionality of my 82SC distributor per the factory, instead of the incomplete Bentley method.

I think the observation would be, we have the two lines, so we need the procedure for the two lines.