[Fot] 123ingition distributor settings

[JS Performance Motoring, LLC]

Hi Mark,
          For a racing setup, you spend most of your time in the upper RPM
range that would be "all in" advance on a mechanical distributor.  I'd
recommend starting with an advance curve that mimics that, then fine tuning
for small gains on the dyno if you have the chance.

My typical starting point for a curve is a very simple line that starts
advancing at 2000 rpm, then maxes out advancing around 4000 rpm.

No added advance below 2000 rpm makes it easier to verify your idle advance
with a timing light accurately.

I prefer to install the programmable distributors at 16 or so degrees
static, NOT at TDC.  This helps with starting, and also improves rotor
phasing at max advance.

On the 123's, the rev limiter setting isn't always 100% accurate,
sometimes you need to program the rev limit a few hundred RPM higher than
intended.

I've attached a picture showing an example of a basic starting point for
the advance curve.



Jason Sukey
JS Performance Motoring, LLC
440.984.7720
jason at jsperformancemotoring.com
www.jspmparts.com
https://www.facebook.com/JSPerformanceMotoring/


On Thu, Oct 23, 2025 at 3:18 PM Mark Cook via Fot <fot at autox.team.net>
wrote:

> All,
>
>
>
> I am installing a 123ignition distributor (laptop programmable) into my
> "project" TR6 race car. Wondering if anyone has this installed on their TR6
> (or 250) race car with triple weber 45 DCOEs.  I thought about downloading
> the tuning curves from the 123 disti in my running #95 TR6 race car as a
> starting point:.
>
> I realize the camshaft would make a difference in the settings, so my
> specs below. Both have 1.55 roller rockers.  Thoughts?
>
>
>
> The "project" car engine has a Racetorations race camshaft, triple Weber
> 45 DCOE and a CR of about 12.5:1.  The camshaft specs are:
>
>
>
> Peak Diff: Exh / Intake / LCA - 108.0 / 107.0 / 106.0
>
> Duration: Intake / Exhaust - 336
>
> Cam Lift:  Intake / Exhaust - 370
>
> Checking Clearance:  Intake / Exhaust - 0.010"
>
> Valve timing (at checking clearance) - Exhaust: Opens 96 BBDC / Closes 60
> ATDC, Intake: Opens 62 BTDC / Closes 94 ABDC
>
>
>
> The camshaft specs in my running TR6 are:
>
>
>
> Peak Diff: Exh / Intake / LCA - 105.0 /103.0  / NA
>
> Duration: Intake / Exhaust - 320
>
> Cam Lift:  Intake / Exhaust - 340
>
> Checking Clearance:  Intake / Exhaust - 0.010" (I think, but not certain)
>
> Valve timing (at checking clearance) - Exhaust: Opens 87 BBDC / Closes 53
> ATDC, Intake: Opens 57 BTDC / Closes 83 ABDC
>
>
>
>
>
> Thanks,
>
>
>
> Mark Cook
>
>
>
>
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>
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