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Old 04-16-2021, 03:11 AM
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Join Date: Feb 2021
Posts: 23
M102.980 timing

Hey guys,
Just wondering if anyone has the timing info for the M102.980 engine.
I'm finding it hard to find this info, unfortunately.
There should be a label (apparently) under the bonnet, but it's probably long gone.
I have adjusted it to 15 degrees BTDC, and she seems a lot happier on the 95 fuel we have here in Australia, but it would settle my mind if I knew what it actually should be
Cheers

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Old 04-18-2021, 01:09 AM
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Location: Long Island, NY
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I happen to have the 1981 TDM handy. These are great little books, findable on ebay and cover all the cars in and just before the date of the book. The Classic Center has them too some times.

The 102.98x engine is listed as follows.
Adjust at 4500 rpm to 32 without vacuum attached.
Then test it at different RPMs. The test values are different based on the distributor installed in your car...

Distributor 0 237 003 022:
@idle, no vacuum, 1+/-3.
1500rpm, no vacuum, 14-18.
3000rpm, no vacuum, 24-28.
@idle, with vacuum, should retard 11-13
4500rpm, with vacuum, should advance 8-12 (to be 40-44, total).

With distributor 0 237 002 066:
@idle, no vacuum, 15+/-3.
1500rpm, no vacuum, 16-21.
3000rpm, no vacuum, 26-30.
@idle, with vacuum, (no spec is given)
4500rpm, with vacuum, should advance 8-12 (to be 40-44, total).

With distributor 0 237 003 025:
@idle, no vacuum, 3+/-3.
1500rpm, no vacuum, 16-21.
3000rpm, no vacuum, 26-30.
@idle, with vacuum, 11-13
4500rpm, with vacuum, should advance 8-12 (to be 40-44, total).

HTH -CTH
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Old 04-19-2021, 03:57 AM
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Join Date: Feb 2021
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Many thanks for that fella, much appreciated
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Old 04-23-2021, 01:53 PM
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Join Date: Aug 2019
Location: Pacific Northwest
Posts: 806
Quote:
Originally Posted by cheezels View Post
...I have adjusted it to 15 degrees BTDC...
As a side note to ignition timing: Don't pay much attention to idle timing because you can't blow your engine up at idle because of bad timing. The most important timing number is the 3000 or the 4500 and no vac. timing. It simulates a full load high rpm condition. That's where you want your timing to be right.

The numbers that cth350 posted are very useful although it would be nice to know which distributor your car should have because they get swapped sometimes.

The distributor 0 237 002 066 looks good because you get 15 degrees of advance at idle (with vacuum that's around 25 so less likely to overheat in traffic) but again the idle number doesn't matter that much.

Verifying your tdc with a piston stop is also not a bad idea since the crank pointer can sometimes be in the wrong place.

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Last edited by christuna; 04-23-2021 at 02:13 PM.
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