DIY - 123 Distributor Ignition Timing with Carburetors

I'm embarking into new territory regarding the potential of the 123 distributor that I think is being overlooked. I am no engine expert but from my research on the web (dangerous I know), that old school tuners used to set initial timing with a vacuum gauge and/or a "highest idle" procedure. From what I have determined, engines typically like more initial or static advance than the owner's manual suggests (for emissions and/or erring on conservative), all you have to do is twist your distributor counter clockwise and see for yourself just how much. This indicates a more efficient fuel burn at idle. Free power. The racer discussions are in favor of setting the idle advance as high as the engine likes, until adding more no longer results in a higher vacuum or idle rpm, then back off a little to compensate for fuel quality etc. Especially if you have a bigger cam like I do. The issue that always comes up is that if you do that, then total advance (when you add in the mechanical advance spec'd in the distributor) you'll have too much all-in and your engine will ping at best or grenade at worst. However this argument is moot with the 123 because you can control the "mechanical" portion with a computer or iphone.

I have said before that one of the great things about the 123 with Weber sidedrafts is that you can adjust the throttle plates to the perfect position in regards to the first progression hole (a critical adjustment for off-idle performance) by compensating either up or down with the static timing to achieve proper idle rpm. This was not possible back in the day so people compensated by opening up the throttle at idle or putting in less than ideal jetting. I have proven this to myself too many times. So this has led me to the next step down the rabbit hole in that now I am experimanting with an even higher static advance because recently, just for kicks I bumped my initial timing up to where the idle responded to the max which turned out to be about 25 degrees btdc. Every engine is different based on age, compression ratio, cam etc and it will tell you when you've gone too far when the idle or vacuum drops off. I then programmed the distributor curve for 11 more degrees from idle to all in 3000 rpm so total advance is still 36 btdc which is in line with spec. No vacuum advance. The only way to do this with a traditional distributor is to have it physically rebuilt, it can be done any number of times and configurations on the 123 in 5 minutes and of course is reversible. So why not said the curious cat.

The "snap" off idle and initial acceleration took me by surprise, it's amazing. One race builder site says this is how they build their engines - a lot of initial advance and only a little mechanical. I've read that Webers "like" a lot of advance. As does a bigger cam. However my Webers at 25 btdc required the throttles to be closed quite a bit in order to keep the idle at or below 1000rpm and so was hard to get the right smooth idle mixture. So my goal is to see what the point is where I can maximize static advace and still keep the throttle plates in an optimal posiiton for idle quality/AFR and will post my findings here for any others interested (if any :p ).

In the meantime I'd appreciate any opinions or other precautions by heading in this direction. The off-the-line acceleration is most defintiely better than my stock timing specs. Here is the curve I'll be tweaking, I suspect it will end up somewhere between 25 and the 15 initial advance I am using now:

Screen Shot 2019-12-20 at 1.09.11 PM.png
 
Last edited:

Ohmess

I wanna DRIVE!
Site Donor
Messages
3,835
Reaction score
1,594
Location
Aiken, SC
If that's the case then yes he could use that and add 6 to the idle advance, I'd like to see those in graph form.

I think it would have to look more like a map than a curve, since vacuum advance would not be constant at every rpm level.
 

Willem Tell

Well-Known Member
Site Donor $
Messages
334
Reaction score
300
Location
Zug, Switzerland
Thanks Both. Unfortunately 123 doesn't provide curves for their "fixed' product. I would have to do direct measurements with my timing light to know the curve for #2, then make the changes and measure again. They've started laying salt now, so I guess this will wait for next Spring!
I'll add to Steve's post when I do this.
 

Willem Tell

Well-Known Member
Site Donor $
Messages
334
Reaction score
300
Location
Zug, Switzerland
Thanks Ohmess, I read up on it, and it looks straightforward. When I can, I will run the RPMs with my timing light and graph the advance (without and with vacuum). It would be good to know what the 123 is doing!

Great thread Steve, leads to a lot of good input!

Happy New Year All!
 

Ohmess

I wanna DRIVE!
Site Donor
Messages
3,835
Reaction score
1,594
Location
Aiken, SC
Thanks Ohmess, I read up on it, and it looks straightforward. When I can, I will run the RPMs with my timing light and graph the advance (without and with vacuum). It would be good to know what the 123 is doing!

Great thread Steve, leads to a lot of good input!

Happy New Year All!

Excellent. When you get to it, please post your data.
 

DWMBMW

Well-Known Member
Site Donor
Messages
748
Reaction score
691
Location
Miami, Florida
Just tweaked my curve based on Steve work (thanks). I got rid of the initial advance at start up and pushed the all in up to 3200 since I have a stock cam.

500 @ 0.0
600 @ 18.0
1200 @ 25.0
2000 @ 30.0
2500 @ 33.0
3200 @ 36.0

I would have loved the performance benefits of the 123 back when I first bought the coupe in my 20’s and drove the snot out of car at 9/10’s all the time. Now in my 60’s I drive a little different but am more amazed at the smoothness and even running that can be dialed in.
 

sfdon

Well-Known Member
Site Donor
Messages
6,398
Reaction score
2,305
Location
sfbay area
Let’s keep in mind that djet for csi and csl has no vacuum advance. The 001 distributor uses the
12111355627 regulator which is vacuum retard.
Would like to see that advance curve!
 

Stevehose

Well-Known Member
Site Donor $$
Messages
11,255
Reaction score
3,477
Location
New Orleans, LA
Did you have to lower your idle speed screw? What was your idle timing before the 18?

Just tweaked my curve based on Steve work (thanks). I got rid of the initial advance at start up and pushed the all in up to 3200 since I have a stock cam.

500 @ 0.0
600 @ 18.0
1200 @ 25.0
2000 @ 30.0
2500 @ 33.0
3200 @ 36.0

I would have loved the performance benefits of the 123 back when I first bought the coupe in my 20’s and drove the snot out of car at 9/10’s all the time. Now in my 60’s I drive a little different but am more amazed at the smoothness and even running that can be dialed in.
 

DWMBMW

Well-Known Member
Site Donor
Messages
748
Reaction score
691
Location
Miami, Florida
So can the 123 provide same benefits as FI while maintaining the visceral sound of the triple webers?
 

TodB

Well-Known Member
Messages
1,226
Reaction score
309
Location
Saint Augustine, FL
I would have loved the performance benefits of the 123 back when I first bought the coupe in my 20’s and drove the snot out of car at 9/10’s all the time. Now in my 60’s I drive a little different but am more amazed at the smoothness and even running that can be dialed in.
I didn’t realize that you had owned your car for so long. Very cool!
 

Stevehose

Well-Known Member
Site Donor $$
Messages
11,255
Reaction score
3,477
Location
New Orleans, LA
no, not even close for efficiency, maybe wide open throttle. But FI can’t hold a candle to the intake music of triples! The 123 just provides the missing link to really dial in the triples

So can the 123 provide same benefits as FI while maintaining the visceral sound of the triple webers?
 

DWMBMW

Well-Known Member
Site Donor
Messages
748
Reaction score
691
Location
Miami, Florida
no, not even close for efficiency, maybe wide open throttle. But FI can’t hold a candle to the intake music of triples! The 123 just provides the missing link to really dial in the triples

I know. Just trying to "fuel" some controversy. FI has that altitude thing also.
 

Ohmess

I wanna DRIVE!
Site Donor
Messages
3,835
Reaction score
1,594
Location
Aiken, SC
Let’s keep in mind that djet for csi and csl has no vacuum advance. The 001 distributor uses the
12111355627 regulator which is vacuum retard.
Would like to see that advance curve!

Woah! Sorry Willem -- I was looking at the upper part of the table which has a set of curves with vacuum advance, including one for the BOSCH 0 231 306 001.
 

m5bb

Well-Known Member
Site Donor $
Messages
2,017
Reaction score
803
Location
Peachtree Corners, GA
Great write up Steve. I have been one of those advance the timing at idle proponents for a number of years. Just didn't help me earlier in the year as I was chasing my tail trying to set too many things as you well know. I also think the M30 motors like higher initial timing like you are suggesting. I will check my settings again in a couple days. It's been running quite well recently but does not like the cold weather start ups.
Just checked my software for 123 to see if it's up to date and yes it was.
 

Stevehose

Well-Known Member
Site Donor $$
Messages
11,255
Reaction score
3,477
Location
New Orleans, LA
UPDATE: I've since aquired the 123 bluetooth model and it's awesome. Just discovered that it has a feature that allows the vacuum advance to come on at an rpm of choice, this mimics the behavior of ported vacuum if you're using a manifold vacuum source. My DCOM triple Webers have one manifold vacuum port per barrel and one ported vacuum take off on cylinder #2 which I do not use because the signal is weak. Today I hooked up tubing to cylinders 3 & 4 and teed them into the distributor. Because of the firing order, this will give the smoothest signal posisble when using only 2 cylinders for source. You could also use cylinders 1 & 6 or 5 & 2 but since 3 & 4 are next to each other I used those two (see pic). At idle my vacuum signal is 13 InHg. At cruise it's about 3-6 depending on load and deccel/over run it's 20 (you'd have to run on the highway to see what your engine does and input accordingly). If you hit the throttle hard it drops to zero. So with this, I made a curve to add 8 degrees advance starting at 2100 rpm if my vacuum is between 1.5 and 22 InHg which captures the operating range at cruise and part throttle. You want the vacuum advance to drop out at full throttle in order to avoid pinging/detonation which is why vacuum advance goes to zero below 1.5 InHg. I'm also running 25 degrees static timing and all in timing of 36 degrees at 3k rpm, so at cruise and part throttle over 2100 rpm I am running 44 degrees for (potentially) better highway gas mileage and cleaner burning. 30 degrees static timing for rpm under 800 which improves cold start idle, and no advance under 500 rpm for easier cranking while starting the engine. Acceleration is great with the high idle advance (and plugs stay clean) and allows me to dial in the throttle plate/progression hole position just right so there is no off idle hesitation. You have to convert InHg from the app's dash gauge display to kP which the app's curve input uses, and subtract from 100, its a little confusing at first, basically 100 is zero vacuum and 0 is high vacuum. A strange quirk. Here are the curves and a gratuitous carb pic:

ltHj8xXilqQNaBEbDKtKZuUtqzU_rNU57uLrA3O8QgOAamgfKmV-DsAQk3K0VUhuysKSxiHlX7Q0XATexee3pnhfOzxp6isMPKKdOsB3bMsVlD-zoraaOEvVsdjWmFmG2WWuinrTgHo_Y_FhuRzIQ9IN4z8qmTta9CT7507aPLxzAgIz6BuHd9WviBv0rY_Pa4INJAjudQsCVEbMVWw-ESC78M3PpXuIHYQivyeksjX4MksLdkYNQn2M7KD63J31JaXAbN7vVxRnwiXxWPO0mjunIoN8Rh1LxruQsUYJKTLgFPMHBHyYzRc7eF03_3KAR8FEPCo7Oj7CMwxeGz9esinqLSxo0Mhn6ao9roIlrqD6doSzryt2tTmqLAOVQznww_F-PRAOFk4tpMoZkPjiG4J_ig-NwLv4QPLge2h0RwniMQHpleNXmVPTHKAis0cE1KG_wv2vpC4_L-rDTZbxOloCgaRn41FT7IJly1A0Zp6vLbOPxlsmewufhOozVcktpeWMXBOEJbKVQCV0WWWX_3KiNUpOx0WHbg4S0RW6ORvG4AZDMEze8smAvl6BH7TKiYzsMqcd5lNpiXknNppfRpFFmzGfVNKLCwv5P-S_dZFrcu60zmD4_zczGNkwdbGjbFr2-rgc2L2tJCdKBjBBjPBrToqkaz8hNog16DYtwpQN0llYdxRx0Q=w586-h781-no


vcBV7yU_8RGAIFrPRAJszSSGYEG2kU7A_DbKrSX_26aYticNsSD-KyRGsh_yHi6cY0tAh18D8tDwhVtiwEbEnfTm-uri2FKaA-tWhGE4jft7K6Ck5K242ismMwXsb2PwnBjP3KIJj8n53I_KD0UucpBH_3Ri6TKb517rSi5WJFzuIItvOMmWPP9vpJxQBUsxSfu3ooeUxJAGex0ltghqz8Lx2XNFcdmUTGVTW1i_zBYOc1m5m5WMzzHt5hGISJoR0lvcnil9zk4u3r2eWMql5phQl2HrX-Tl0GZeStPHpt4U1HJOX3X0qupXb3UIJAQrIzMRc2cPhsbexHXnbjq4QkcvheZO_Asth90N6pv3RG84eRRWomFeCs_PnSfi0xa4KAhkO2__-RKdu5jgQh2KYCPMebBG0nTJEE2KbiVrsMq04cPQn8NtUU0yU_5h-ZMnBB0aQFoOw5wRVI3_tHzBpX7_xY1REWXLpzhIsune0HaEiA93ILRD8KdpPn1E0yaItWRJ9OwMGF-NFZYnB9tDZt9bhH1jsUmyCwZjvQcW1J1EPICVkc60USwSsvdLA586Zc6Aa8DwhazOlnz5Lxwlyr7suis5Bd1wy_ELc1AGT3h1ciQboRb1LNy8oetR5NEpfsNYpj4eTgmiIjW8xMegZtqguZ24a4U8c27SZb2GwTIV_-the4qePQ=w440-h781-no


vNPstUZBCUdHNYGnjrdo-HXk8RATDjEhUulQ34c2j4JEvJd1qju3oqaT4Ejyop27MNXj5OKGau2FitlKBCDDGuBdIwKscYOX2gTFwBxSoLfYMPucFCpg0gtt4IKeJotbjlmF0w7KuVUDczCEuBKxPY_wjH71jetU9I4P6AHVivjMADIweNdgo_YOGtcC-62L6Ap9MZ_2xtbYYpKtDpXFC2DleCFcDRR3FLjW5SpD560tGAAOYZqDfqgqZIj0EFpIisGIZ5abpmvjPZP4PUhsuki2pt_QNV4SDzYZ0BIhroT1S2Mf8p_N77nPzx4OwL4IEGyDnSsvxZr9LnX8W0JAOR4K8jTyO5KXtvA-Nv_14toEjSOO49YmWovqOyYls1xmCwrWp8-HPvN1-fMhxg_PHiS2RWlJqtP7bcyzlOrQymmXbZQ-l5AdkGSnqmLFmsWydvElLII247KnUHRfowCQcYbcLI2VPHyJPUqhd0BoR_ysqsrUKKV7Cq089sgL9FBXw6YjrLa1o1YLsUUVqg3cBQ3rr6Ca6a98RHbYIDBkGhL3lcNCG8VQXZjlOMpwQcrRGS3aSRc_vfYj4-IXn77BTcGo30oBRGJGyu37hnNcwsoQ1RIUN6-yl303-U7QeRHetqbQZwAaD4BtyfLfM1rKD0YsqGzA_ArNcoNRUY1mK3BoyDVmVpQfiQ=w440-h781-no
 
Last edited:
Top