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Discussion Starter #1
I just received my 123 distributor from IAP and am getting ready to install it in my 71 Spider with a 1750 converted to Webers (SPICA manifold). The car has the stock SPICA cams (for now), Blue Bosch coil and a stock exhaust system. I'm using a Euro Airbox on the intake.

I've researched the threads on removal and installation of the distributor itself, and found this -spider-distributer-removal.html
and I think I've got it down, with just a couple of remaining questions:

1. How far would I need to roll the car to find TDC in the worst case scenario? A sloping drive on a rainy day makes that an undesirable option. Can I instead just jack up the rear, put the car in first(?) and spin a tire to find TDC?
2. The RML says that it has an LED light with which to set the static timing. Is that likely to be very close, or am I definitely going to have to play with the timing light, afterwards?
3. The RML comes with a selection of 16 Curves, chosen by a Set-screw covered selector on the bottom of the distributor; listed here in the 123 Installation instructions; third page.

The obvious choice is Curve # 8 for the 1750 Spider. However are there any of the others that are 'better' for my stock/ + webers street engine?

I did find this post which came to a consensus that the the #8 curve isn't that great but there was no consensus ever reached between curves 1, 6, or E.

4. There seems to be a lot of discussion of 6 or 8 degrees off TDC for setting the static timing properly.... however, ain't no degree marks on my pulley and I'm probably not up to measur[ing] the diameter of the pulley, calculating the circumference - pi*D, then measuring the distance from TDC to the static timing mark as Circumference * d/360 where d is the number of degrees of static advance while the engine is in the car and the fan and shroud are installed. Any suggestions here? Anybody already make a template put on the pulley?

Thanks guys
 

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1. How far would I need to roll the car to find TDC in the worst case scenario? A sloping drive on a rainy day makes that an undesirable option. Can I instead just jack up the rear, put the car in first(?) and spin a tire to find TDC?
My tires are about 24" in diameter. So their circumfrence is 24 x pi = 74.4" Assuming you have a 4.56 diff, and the car is in 4th gear, the engine will turn 4.56 rotations with every full turn of the back wheels. But, since you have a 4 cycle engine, you might have to turn it two rotations to get to TDC. So 2 X 74.4 / 4.56 = 33" or about 2-3/4 feet.

Can I instead just jack up the rear, put the car in first(?) and spin a tire to find TDC?
You definitely do NOT want the car in first gear when pushing it! Fifth would be best. Remember, now the power is going from the wheels to the engine, so things work backwards from normal.

You could try just turning the wheels with the car jacked up, but that takes a lot of torque - somehow, pushing the car is easier. If you remove the spark plugs so you aren't fighting compression, it will make the engine easier to turn.

You could also get it close to TDC using the starter + trial-and-error, and then fine tune the position by pushing the car back & forth.
 

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I got the 123 specifically so I could play with all the different advance curves. So, I would just start with whatever is suggested, #8 it looks like for you, then try a different curve every few weeks, and make note of the differences. It's fun.
Also, you said the RML has the LED, but the RML is the one with mechanical advance, and no LED. But you don't need the LED anyway, just roll the car to TDC and have the rotor pointing to number one, before you take out the old dizzy, then put in the 123 the same way.
I found that there were two or three advance curves that were kind of similar, and pretty close to all being good enough. What makes more of a difference is the amount of static advance there is when you tighten down the dizzy. And that's a lot of fun to play with too.
Next thing to play with is DOHC timing. That's really fun too.
 

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Yeah, like Jay said you'll need to roll the car in fifth. It's also generally good form not to turn the engine backwards: probably won't hurt anything on a car with a timing chain like the Spider, but best not to tempt the fates I always say.

If you can get it somewhere flat that would obviously be best. You can roll it forwards in fifth, then if you run out of room back it up in neutral and then go again. Even if you have a small garage this'll work fine.
 

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Ed, that's a great thread with a ton of good info!
`

The 123 is still going strong. Ask me if you have any specific questions as there is a good chance that I have at least researched it and maybe experienced it.
 

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Discussion Starter #8 (Edited)
Success - Thanks!

Just checking back to report success in installing the 123 Distributor, and to say thanks for all the help. It was actually fairly easy in the end; the LED to comfirm that static timing is correct is a great feature of the 123.

For other novices who may read this in the future, here are a few things I learned along the way:

1. This is best undertaken with two people. I suppose it could be done alone if you've done it before, but first time out, bring a friend. In total, we spent a couple of hours however, realistically, after you've done it once, you could probably pop it out, change the curve, and go for a drive in 30 -40 minutes.

2. The roll-forward-in-5th/plugs-out approach to find TDC works well and easily.No need for elaborate calculations (fortunately!:D). My friend who was helping me taught me a good 'pirate tuner' trick from his 60's Hemi-Dart days that is worth repeating:

As the two of you roll the car forward, put your finger over the plug hole for #1. You will feel the compression building as you approach TDC. You will be close enough by feel to stopping at TDC that you can then finalize by just using a flashlight to see the timing pointer and gently moving the car back and forth. Since you're only moving it an inch or so either way, I don't think there's much danger of jumping the chain or anything by moving the engine backwards.

2. Setting the static timing with the 123 is very easy because of the LED. However there are a couple of small tricks that can save you some time.
a. Figure out roughly which direction you will want the lead wires to the coil to point on the new coil before starting.

b. Turn the rotor in the new distributor so that the LED is already showing through one of the four holes in the aluminum disc under the rotor.

c. Then pull the old distributor, noting the alignment of the adjustment/lockdown plate and the dog-teeth on the bottom when they are pointing to TDC. You will want to replicate that alignment between the plate and the dog-teeth when you put the plate on the new distributor body.

d. Even after removing the lock-down bolt on the alignment plate (not the attachment nut to the block) it was a very tight fit on both the old distributor shaft and on the new, as it should be. To remove it from the old shaft, some gentle persuasion with a flatblade screwdriver and a SFH were required. To fit it to the new shaft, remove the O-ring and then spread the gap in the alignment plate with a flat blade screwdriver, leaving the blade of the driver in the gap until you've slid it up the new distributor's shaft till it touches the bottom of the distributor body. While you are doing this, you want to recall the aligment of the dog-teeth to the slots in the block, the direction in which you want the coil leads to point, AND to make sure that the LED is visible through the one of the holes in the plate. Yes, you can almost mostly accomplish all three things, probably by sacrificing the ideal shortest-route for the coil leads... the least important point of the three.

d. Now drop the new distributor in for a test fit, and make sure that the position of the alignment plate leaves you room in the advance/retard slot to rotate the distributor either way. Again, sacrifice the direction from which the coil leads depart the distributor body because that's actually unimportant except for cosmetic purposes.

e. If you've done all of the above, the distributor will drop right in, and when you hook up the positive lead per the instructions and turn on the ignition, you will be pointed at TDC with a pretty LED gleaming up at you through the hole in the aluminum plate. Now you can tighten down the bolt on the lock plate, leaving the nut off the block/adjustment slot stud.

f. Now pull it once more and pull the set screw out to uncover the 16 choices for the advance curve, if you hadn't set it already during the open-package-and-tinker-with-new-toy phase. It's nice to make sure it's really on the curve you want before you bolt everything in.

g. Make sure that you have the plug wires on correctly before fitting the cap - even if you've done everything else correctly, the car is not going to fire if your plug wire sequence is off by one plug e.g. #1 plug wire hooked to #4 on the cap or some other variation.:blushing: Remember if it doesn't just crank right up, the simplest solution is the most likely; especially since you've had the reassurance that the distributor is installed right because of that glowing LED.

h. You will be able to retard the timing well enough to do a test run just by turning the distributor till the point where your friend at the wheel reports a decent idle speed. My car is currently idling a little faster than it was with the old distributor, I'll detail tune it later. For now, tighten down the advance/retard nut on the slot and you're ready for your test drive!

Overall Improvement: Even using the curve that is the 'match to the original' curve built into the Marelli, the engine is much crisper and revs more quickly. Although expensive, I'll say that this distributor is a part that actually makes a noticeable improvement to the way the car runs. I will install new plugs and run it for a week or so before I try any of the other curves.

Post Script: There was nothing easily noted as being wrong with my old distributor, in that there was no wobble, and no marks on the advance mechanism. Still cleaning and lubing the advance mechanism hadn't solved the problem of sootly plugs and a intermittent stumble under acceleration at 5200- 5300 (indicated) rpm. Most of the improvement attained here could have probably been achieved with a rebuilt distributor or perhaps even just with a good cleaning, lube, and replacement of the springs on the advance on the old one for most people. . Still, it's very nice having the option of changing the advance curve, and given that my distributor was more than 40 years old, a new replacement was the smartest option for me. YMMV.
 

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I did mine a while back but I found it best to take out spark plug #1 and, put it in neutral, and turn the engine with a breaker bar and the right size socket. place a long screw driver in plug #1. as you turn the engine the screw driver will rise and as soon as it starts to go down stop then back it up until you find the middle by marking the wheel position.

hope you got it running by now but just sharing an old shade tree mechanic trick.
enjoy
 

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Most people I know use Amoreno's method ^

Is there a lot of distributor slop with the Alfa distributors? I'm trying to figure out how much spark scatter this even with the 123 ignition. I would really like to get a more modern advance curve on the dyno but I'm worried the distributor bounces around so much that the fully programmable 123 might be a waste of time and that I should mount and EDIS wheel instead and use a megajolt or something.

Any advice for me?
 

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Most people I know use Amoreno's method ^

Is there a lot of distributor slop with the Alfa distributors? I'm trying to figure out how much spark scatter this even with the 123 ignition. I would really like to get a more modern advance curve on the dyno but I'm worried the distributor bounces around so much that the fully programmable 123 might be a waste of time and that I should mount and EDIS wheel instead and use a megajolt or something.

Any advice for me?

I'm not exactly sure what you mean. There can be a lot of slop with a 40 year old dizzy, Alfa or otherwise. But a 123 is the entire distributor and should be dead nuts. I suppose there could be slop from the connection on the oil pump but at that point I would be worried about the oil system nit ignition.

I don't have the fully programmable 123 but I do have older 123s on several other Alfas and they are rock steady. If you want to customize the advance curve I couldn't think of a better set up then the programmable 123...
 
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