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Old 04-19-2017, 12:10 PM   #1
free244dl
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Default Distributor stuck, vacuum advance vs μS

I am in the middle of preparing my 78 244 with the b21f for microsquirt. The distributor in the block right now is thoroughly stuck in place, and I have managed to rotate it only about 5 degrees trying to get it out, with using a hammer (yes I removed the retaining bolt). I am trying to figure out, do I actually need to remove it, and if so, how do I do that?

I don't know the part number, but is a bosch unit with vacuum port on both sides of the diaphragm. I have a spare distributor in my toolbox that has only one vacuum port that I was planning on locking the advance mechanism in, then swapping it in. The plan is to use the hall sensor to pick up cam speed data and use the existing coil and distributor for spark output.

One of the reasons I planned on replacing the existing distributor is that at one point, I tried starting the car with the cap off the disty and the little retaining clip caught on one of the fingers on the hall reluctor ring (I think that's what happened, I didn't notice at the time). I have since bent it back into shape but I am not sure if it is right, because I got fed up with the k-jet and removed it
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Old 04-19-2017, 12:28 PM   #2
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You would have to immobillize the vacuum advance/retard function I think and make sure your Hall pickup is in working order to leave it in place. But you should be able to make ms work with wherever it's placed at.
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Old 04-19-2017, 12:36 PM   #3
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Quote:
Originally Posted by VB242 View Post
But you should be able to make ms work with wherever it's placed at.
This is not true for two reasons:

1. MS in basic trigger mode defines cranking timing by the offset of the trigger edge. This means you have to actually set the distributor where you want your cranking timing.

2. Rotor phasing. You can't just drop a distributor in and tell MS "it's here." The rotor has to be properly phased with the post(s) on the cap to prevent cross-firing and excessive rotor wear from firing out of phase.

In most cases, where it was with OEM timing spec will work with MS provided you lock out any mechanical advance in the distributor.
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Old 04-19-2017, 06:10 PM   #4
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OK, I can smack it back to the stock location. Its been soaking in PB blast for 5 days and it is still stuck. Any ideas? I would prefer to take it apart on the bench than in the car.
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Old 04-19-2017, 07:59 PM   #5
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Keep soaking and wiggling it, somebody put it together a long time ago, it can be taken apart.
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Old 04-19-2017, 09:04 PM   #6
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You need to somehow get your old distributor out and replace it with a LH2.2 distributor that's already "locked down" from the factory. MegaSquirt does not have any sort of anti-advance tables to counteract any vacuum or rpm advance built into the distributor.

Also, someone else on here posted .msq's for a basic LH2.2 disti setup. I think they eventually were able to use "Trigger Return" mode -- this mode uses one edge of the crank sensor (in disti) to trigger spark immediately during cranking, and the earlier edge to allow adjustable MS advance during running. IIRC this was partly documented on diyautotune's website for a Volvo 240 install.
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Old 04-20-2017, 12:05 PM   #7
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Thanks for the replies. Ill go beat on it some more after I get home from the junkyard on friday.
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Old 04-24-2017, 11:48 AM   #8
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I finally got it out. After working it back and forth for 5 min, I was able to get a pair of screwdrivers under it and pry it out. There was a bunch of corrosion buildup that looked like sandy earwax lol.

This distributor is decked out with mechanical advance and vacuum advance/retard. Has anyone done a write-up of disabling these features? I could just zip the mechanical part together with the Mig, but not so much on the vacuum advance part.

Also, the reluctor wheel with the 4 fingers I mentioned in the OP has the one finger that is intentionally out of time with the others, and that is the one that is damaged. I was able to bend it straight, but it cracked and I do not believe that it will stay intact for long. Do you guys think it is possible for me to tack some extra metal in with a Tig machine?
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Old 04-24-2017, 12:00 PM   #9
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Given all that, Bob's advice is best at this point. Just find an LH 2.2 distributor and rock out.
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Old 04-24-2017, 12:02 PM   #10
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I'm using a 2.2 distributor
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Old 04-24-2017, 12:23 PM   #11
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Ill look for one. I did not see any Volvos at the JY older than '91 on Friday, so I might have to go to a different yard.
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