All about Timing - Correcting and Adjusting your 258's Spark Advance.

Рет қаралды 518

Ай бұрын

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/m...
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.

Пікірлер: 15

@stephenburke9909 Ай бұрын

Awesome video my friend. I'll be driving the Eagle down in the next few months and we'll have to test my car. I just want to see the results on the ol dot matrix printed paper for nostalgic reasons :) What an awesome piece of equipment to have laying around hehe

@olik136 Ай бұрын

that is way more complicated than I would have thought. My 60s Volvo has no vacuum stuff at all- all you do is turn the distributor until the engine runs best (which is very easy to hear) and that is it. You can check the markings with a light gun- but it won't get you any closer.

@ReaperRestorations Ай бұрын

i'm having the same issue on my '85 and another issue with the sol-vac unit not responding to loads on the charging system, AC, etc. its like it's not receiving the tach signal. it doesn't bump the rpms up no matter what adjustments i make. i've followed the procedures in the manual, but for the timing there seems to be several versions of how to set it properly

@CelGenStudios Ай бұрын

Verify that the diode module (black box usually next to the wiper motor and combines the AC, defroster, headlight and computer signals to a single wire for the solenoid wire without backfeeding) isn't damaged.

@ReaperRestorations Ай бұрын

@@CelGenStudios interesting. would that also affect the tach feed to the computer (or vice versa)? i got an Eagle tach gauge cluster off ebay but when i hook up the tach it doesn't work. could be a faulty unit, or could confirm that i have no signal (which would make sense). ill be checking that box to see what the deal is

@CelGenStudios Ай бұрын

In '82 the distributor reluctor goes straight to the Duraspark and then out again as the TACH signal for the computer, the optional tachometer and the negative post on the ignition coil. Starting in 1983 they added a knock sensor and upgraded the computer to handle it, but now the reluctor goes straight to the computer, the computer can then directly retard spark timing by itself and then goes to the Duraspark module which then gives you the TACH signal for the optional tachometer and the negative post on the ignition coil. In both cases the TACH signal will be a dark green wire. If the computer detects an erratic or low RPM (and it can only do so using the distributor reluctor) it will use the SOL-VAC to try and kick up the idle using the Idle Speed Relay. It, the AC, the defrosters and the headlights all pass through mentioned set of diodes to prevent backfeeding but any one of those being turned on should get you battery voltage exiting the diode module.

@DandyDon1 Ай бұрын

Read The FRIENDLY Manual. :o)

@DandyDon1 Ай бұрын

How will these adjustments effect your SMOG test?

@compu85 Ай бұрын

So did it drive better??

@CelGenStudios Ай бұрын

Yes and no. Yes in that I could accelerate and get up to highway speeds far faster than previously and it was considerably more responsive taking off at a light or stop sign, HOWEVER it became considerably harder to maintain a stable curb idle on a hot soaked engine. Occasionally it would simply stumble and stall. I didn't mention this in the video as there's some instructions that through the Internet are inconsistently described and I have not fully tested enough to be confident talking about in a video, so follow the suggestion below with caution. Two things that you need to factor into timing adjustments, prior to adjusting your idles: -On an average day/week/month/year of driving the car, How many thousands of feet are you above sea level? Your timing will change by half a degree for every 1000 feet. Eventually for AMC/Jeeps you exceed 5000 feet and there is a physical jumper and alternate timing spec you need to pay attention to. Modern vehicles can compensate for altitude using the MAP/MAF Sensor. -Do you use Ethanol blended (Regular) gas? Ethanol blends like to more readily vapor lock and less readily ignite (at lower cylinder compression) than gas did 40 years ago. That will also affect your timing by a degree or two. After this video the vehicle was test driven and the above symptoms were noted. The timing was dialed back to 12.5 degrees BTDC which resulted in an engine that both accelerated good (this isn't a racecar, so 0 to 60 in 15 seconds is already "better than average" for an Eagle) and could handle a curb idle.

@computeraidedworld1148 Ай бұрын

How comes the vacuum hoses need to be plugged?

@CelGenStudios Ай бұрын

Open hoses result in vacuum leaks. Vacuum leaks mess with the engine while you are trying to make adjustments.

@computeraidedworld1148 Ай бұрын

@@CelGenStudios oh, yeah duh

@SkoddieAltair Ай бұрын

Having any part of setting the timing involve putting the car in drive and opening the throttle is just feral. I guess the wear on the transmission is minimal given that this happens for a fraction of its life, but everything about putting load on the torque converter while not moving hurts. I guess that's the point for setting the idle though? 🫠

@compu85 Ай бұрын

That doesn't wear the transmission at all. If you raise the rpm first then slam into gear that's bad, but going into gear first then raising rpm just warms the fluid some.