Installing 123 Ignition Distributor - advice sought

[VWporscheGT3]

[heimlich]

Good call on the 123.
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[RedSquare]

[raygreenwood]

[RedSquare]

Definitely leaks around the throttle plate.

Started the car up and let it warm up to operating temp. (And pulled the AAR hose off of the air cleaner and plugged it after it was warm.) Once warm the oscillation started as expected. Then, before I took the intake boot off of the throttle body, I sprayed carb cleaner around the back plate and near the throttle shaft, but the idle didn’t change, so I’m assuming there is no appreciable leakage at either of those locations.

Took the intake boot off and started putting the ring of modeling clay in place, but hadn’t bothered to shut the motor off, which proved to be a mistake. The air being pulled in through that bypass passage that runs under the throttle shaft (or whatever that passage is) is significant and it grabbed a bit of my modeling clay rope and…THUUUUP!…sucked it right in. I had the presence of mind to quickly cup my hand over the intake which immediately killed the motor and was then able to fish the little bit of modeling clay out of that passage. Whew….

So, with the motor SHUT OFF I placed the ring of modeling clay around the circumference of the throttle plate, then restarted the motor while remembering to leave the darn throttle alone. Started up fine, but with an obviously lower RPM. Maybe 150 rpm’s or so lower than without the clay. I didn’t measure it - just looked at the dash tach and estimated, but it was meaningful lower. Seemed like it still had a very small oscillation even with the clay, but either I imagined it or it was very small.

Then pulled the modeling clay back off. That was harder than I expected because I hadn’t cleaned the throttle body before I put it on, so there was some general grunge (not a lot) which didn’t make it any easier. Also, the clay got warm and didn’t hold together as well as it did when cool, so it took a bit to get it all off of the throttle body.

Things I would do differently if I had it to do over again:

1. Clean the throttle body before you put the clay on.
2. Shut the motor off before you put the clay on.
3. Wait for throttle body to cool before removing clay.

One thing I got right on accident was that I used white modeling clay. That made it easier to see when I was trying to get it off than it would have been had I chosen a dark color.

So now what? Is there a remedy for a leaky throttle plate?

[KTPhil]

Because it is designed to bypass with that screw/nut/hole that sucked in your clay, this throttle plate is not required to seal completely, just consistently. It may not be your problem.

I have never had to do so, but many use clamps, or at least tight zip ties, on both ends of the four stubby hoses connecting the intake runners to the plenum. I used a slight smear of sealer on mine when I put it together, even if they are tight. However, with age and heat cycles, they can stiffen, and if you ever loosen the plenum or runners, they can develop hard to find leaks, even though they look fine.

[RedSquare]

You are talking about these 4, yes?

And you’re saying that the throttle plate leakage just adds to the air that the idle set screw allows? Makes sense if so.

[KTPhil]

Yep.

[RedSquare]

I put a pair of zip ties on either end of all 4 of those stubby hoses, then ran it again. Seems like the oscillation was less pronounced after that then it was in the video I posted earlier in this thread, but I’m not entirely sure.

Regardless, I took the car for a short drive after I got it all buttoned back up, and it drove really well. Hard to describe what was different - the engine just felt smoother to me. Not like it had more power or anything. Just smoother. Maybe it was, or maybe I just thought it was because I changed to the 123 Ignition and expected it to be better. But it really did feel noticeably smoother to me.

If nothing else, I don’t have to concern myself with distributor maintenance anymore, and that is something.

[KTPhil]

Those hose stubs are sometimes hard to find.

Jbugs has them, but categorize them as Bug parts, not Type 3.
https://www.jbugs.com/product/043133241.html
But these fit correctly/tightly.
If you bother to replace these, you should go whole hog and replace all the runner/injector seals, so you don't have to for many years. This would include sealing the bakelite plates (since no one sells the super-thin gaskets you used to be able to get--use a thin smear of fuel-compatible silicone non-adhesive sealant), injector tip seals, and these stubs. A PITA job with the engine in the car, so do it all at once. Replace the 1 or 2 hoses that fit into the plenum while you are at it.

Your clamped stubs may be good enough for now, though.

[raygreenwood]

[KTPhil]

Ok, I'll add to this thread instead of my other \troubleshooting threads, since this is just about the 123.

I installed it and timed it and ran 200 miles yesterday using the "F" curve, and although it runs well, it is down on power from the stock unit through the mid range.

Comparing table entries:

Can I select the "E" curve (intended for the Type 4), to see if the earlier advance helps? The current F setting feels sluggish and I need to rev it higher, making it peaky, which makes sense if it reaches just 21 degrees and is all in by 2600 rpm. The higher 30 max of the E curve might be a bit much, but the slower rise might make it okay.

AS long as I am not pinging and overheating, I presume the setting can work and might help. Any reasons not to do so?\

And what does "for tuning" mean?

[Tram]

[KTPhil]

Thanks, Tram, I'll experiment. I'll also be recalibrating the MPS with my O2 sensor, but I want to get timing right first.

Does changing static/idle timing also affect the timing of the trigger contacts, like in a stock distributor? I would presume so.

Do we have data about the entire curve, or just the max/rpm info in this table?
Anyone else experimented with the curve choices?

Thanks, all!

[KTPhil]

I wonder if others like "B" (generic 1600) still work the trigger contact wires?
25 max for mechanical (plus vacuum) sounds about like stock.

[heimlich]

Looks like F curve is for tuning. Appears to be a 009 curve which is not going to give you anything close to stock.

D is usually a curve for Porsche. It ramps up very quickly. The stock curve at least does this.

What is your stock distributor is I can help match it for you?
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[heimlich]

I sent a message to the 123ignitionusa. They said they do not have the curve data.

Maybe one of you whom have bought one can ask for this data?
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[KTPhil]

[heimlich]

Here's what was sent to me:

Curve 0:
500 0
1100 0
1600 10
3800 24
8000 24
Curve 1:
500 0
1100 0
1600 14
3800 24
8000 24

Curve 2:
500 0
1100 0
1600 10
3800 24
8000 24

Curve 3:
500 0
1100 0
1600 14
3800 24
8000 24

Curve 4:
500 0
1000 0
1500 8
2000 12
2500 15
3000 18
8000 18

Curve 5:
500 0
1100 0
1550 13
2200 13
4000 22
8000 22

Curve 6:
500 0
1200 0
1500 9
3800 23
8000 23

Curve 7:
500 0
1150 0
1600 14
2200 14
3800 23
8000 23

Curve 8:
500 0
1100 0
1600 21
2100 21
3600 31
8000 31

Curve 9:
500 0
1250 0
1500 9
3750 23
8000 23

Curve A:
500 0
1250 0
1500 9
3750 23
8000 23

Curve B:
500 0
1000 0
1300 8
3400 25
8000 25

Curve C:
500 0
800 0
1200 18
3100 35
8000 35

Curve D:
500 0
800 0
1300 15
3100 30
8000 30

Curve E:
500 0
1100 0
1600 18
3200 30
8000 30

Curve F:
500 0
1100 0
1300 5
1700 5
2600 21
8000 21
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Not all parts are made the same. NOS OE/OEM parts made mainly in West Germany, Early Germany, and Early Brazil are where VW produced the best quality parts and best fitting products.
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[Erik G]