Uploaded May 2024 | Updated September 2026, 2 weeks ago
We trust a mechanic to know what they are doing. After all, they went to school for this. Sometimes mistakes are made and they are hard to notice.
In this video I discover that a previous (and poorly done) engine installation had the engine broken in and run (part of this is my fault for reasons I explain in he video and I won't deny that) with a mere 5 degrees of spark timing BTDC. On an AMC straight-six with no computer this is "okay" but a 258 with Computerized Engine Control needs 15 degrees (or a few degrees less as you go up in altitude) or as it turns out, the engine runs but wow it feels anemic.
We'll be following AMC Service Bulletin I.S. 12E, instead of the 1982 AMC Technical Service Manual to check and adjust the engine timing. You can find it on the Internet Archive.
archive.org/details/is-12-e/mode/2up
This bulletin is especially important for 1982 model vehicles (not jsut the Eagle!) as I have found the instructions commonly shared from the TSM results in an unacceptably incorrect timing. We'll be using a Sun Modular Engine Analyzer and its variable timing light to more easily show what I'm doing. For you at home all you need is a handheld precision tachometer and a standard induction timing light. I strongly advise against the old fashioned "set the ignition timing with a vacuum gauge" method. A second person to assist is also strongly suggested, especially for in-Drive idle adjustments, which must be done after the timing is adjusted.
Remember to follow me on "X" at @CelGenStudios to keep up to date on what I am doing and what might be happening in the next video.
We trust a mechanic to know what they are doing. After all, they went to school for this. Sometimes mistakes are made and they are hard to notice.
In this video I discover that a previous (and poorly done) engine installation had the engine broken in and run (part of this is my fault for reasons I explain in he video and I won't deny that) with a mere 5 degrees of spark timing BTDC. On an AMC straight-six with no computer this is "okay" but a 258 with Computerized Engine Control needs 15 degrees (or a few degrees less as you go up in altitude) or as it turns out, the engine runs but wow it feels anemic.
We'll be following AMC Service Bulletin I.S. 12E, instead of the 1982 AMC Technical Service Manual to check and adjust the engine timing. You can find it on the Internet Archive.
archive.org/details/is-12-e/mode/2up
This bulletin is especially important for 1982 model vehicles (not jsut the Eagle!) as I have found the instructions commonly shared from the TSM results in an unacceptably incorrect timing. We'll be using a Sun Modular Engine Analyzer and its variable timing light to more easily show what I'm doing. For you at home all you need is a handheld precision tachometer and a standard induction timing light. I strongly advise against the old fashioned "set the ignition timing with a vacuum gauge" method. A second person to assist is also strongly suggested, especially for in-Drive idle adjustments, which must be done after the timing is adjusted.
Remember to follow me on "X" at @CelGenStudios to keep up to date on what I am doing and what might be happening in the next video.
