123Ignition problems

[twistedtree]

In another thread I mentioned that I installed a 123Ignition replacement distributor in my '71 142E. At first it seemed good, probably because my old distributor was so bad, but the more I've used it, the more issues I've found.

If you aren't familiar with the 123, it's a replacement distributor that includes electronic ignition and timing advance, and for some models (like mine) electronic triggers for the fuel injection. In theory it's a drop-in replacement.

The problem I've found is that the 123 is programmed for vacuum advance where all the B20B and B20E engines are equipped with vacuum retard distributors. If you just drop in the 123 and connect the vacuum line, you end up with a vacuum retard manifold port connected to a vacuum advance distributor. The result is timing advance that is completely messed up.

There are two workarounds with varying levels of complexity and varying results.

Easy workaround, so-so results: A simple partial workaround is to just disconnect the vacuum line and plug the manifold port. This disables the vacuum component of the 123 advance. The good news is that the incorrect programming is no longer working against you, so the car runs better. The bad news is that you are foregoing one of the most important features of vacuum controlled timing, which is a quick boost in advance when you hit the gas off an idle. Drivability will suffer taking off from a stand still, and in stop and go traffic.

Harder workaround, pretty good results: The better performing workaround is to convert the engine over to vacuum advance so it correctly matches the 123's programming. This involves plugging the retard manifold port, and finding an advance port. Hopefully such a port exists on your car, otherwise you either need to start drilling holes into things you should be drilling, or you are sh&t out of luck. With the vacuum advance 123 correctly ported, it works quite well, but it's hardly a drop-in solution.

If you are wondering what the difference is between an advance and a retard port, it's quite significant and is based on where the port is located, either before or after the throttle flap. A vacuum retard port comes off the manifold or other location AFTER the throttle flap. A vacuum advance port comes off the intake BEFORE the throttle plate. A retard port has max vacuum when the throttle is closed, and vacuum drops when you open the throttle. A vacuum advance port has zero vacuum when the throttle is closed, and it increases when the throttle is opened. They work exactly the opposite of each other, so you can see how connecting your distributor to the wrong port will create a real mess of things.

Of course the preferred solution is for the 123 to be correctly programmed for B20B and B20E engines, but they have told me they don't plan to do that. So if you are thinking of using a 123 in your car, go into it eyes wide open about the modifications needed to get it to work properly.

By the way, does anyone know whether cars delivered outside North America were equipped with vacuum advance or vacuum retard? From what I can tell all cars world-wide are vacuum retard, not just the US and Canada. Does anyone know otherwise?

By the way, once the car is modified, the 123 works pretty well.

[whispacloud]

I don't know but if you get it working right you should make a write-up.
That's pretty interesting stuff.

[vvpete]

The '71 B20B w/HIF6 carbs came with either vacuum advance distributor (Bosch 085) or the more common vacuum retard dist, commonly used with the Strombers carbs, which NEED the retard to attain decent acceleration at low rpm's (and even then they are pretty slow).
When I needed a replacement dist for my '71 145 I got the vacuum retard dist and simply didn't use the vacuum.
On the carb dist the mechanical advance is quite good all by itself, but a carb dist that relies on vacuum for advance has little advance from the mechanical flyweights, and have small mechnaical advance compared to one that relies entirely on the mechanical advance, like the retard dist to pull back timing against the mechanical advance. So that said, the vac retard dist when used w/o the retard diaphram will give more mechanical advance.

Pulling the vacuum off the carbs setup is a lot easier than from an EFI manifold, though, especially when it's not set up for it.
IIRC the K-Jet w/Bosch dist from '73-74 uses vacuum advance, so a manifold from those cars will have the ports you want.

[JayDee24ca]

I've been driving my 1800S with twin HS6 carbs and a 123 dizzy for about three years with the vaccuum port plugged on the dizzy.
I only this weekend found a vaccuum port on the upstream side of the butterfly on the rear carb. Apparently I have been driving the car for all this time with that nipple uncapped. No wonder I could never get this car to run as well as it should.
Anyway, as this is is an ADVANCE port (upstream from butterfly), will I see an improvement if I connect it to the as yet plugged 123 port?
Thanks
JD

[twistedtree]

Yes, I think you will notice a nice difference. Having the port un-capped won't be a problem, but I think you will find not having proper advance has been a problem.

Maybe one of these days 123 will acknowledge this problem.

[JayDee24ca]

Originally Posted by twistedtree

Yes, I think you will notice a nice difference. Having the port un-capped won't be a problem, but I think you will find not having proper advance has been a problem.

Maybe one of these days 123 will acknowledge this problem.

Thanks man! I'll finish this carb tune with the nipple on the carb plugged (as per tuning spec) then run a line from it to the 123 when I am done. Perfect!
JD