The original symptoms sound like a vacuum leak. This can be overcome, somewhat, by enriching the carb but idle often suffers. Advancing the distributor timing might help too but it's not really addressing the vacuum leak. I could be wrong but it's easy to check. It's not too hard to find top-dead-center without timing marks either.

Kelley

Marcel:

Thanks for dropping by.

With is engine SEEMINGLY running best on 12 deg static timing I suspect three things:

1. He is trying to use a timing light to set "static timing" - one of those fancy ones where you can pre-set advance.
2. His timing marks may be way off.
3. His cam timing has slipped.

His comment about it suddenly gulping more fuel suggests something is way off.

Thanks again for giving us the 123!

Cheers!

One of my old colleagues asked me to come back here to see if I could resolve this problem. Fortunately for you I've seen this problem before:

 

"I re-set the static timing to 12 degrees BTDC (from zero where my Prius mechanic had set it). This was the primary change, and made the Mini run much more smoothly."

 

The problem is you don't know what you're doing. When I designed the 123 I tried to make it fool proof, but that's where I made a fundamental error: underestimating that potential.

 

Rennie, read the damn manual, set the distributor the way it was designed and if your engine still runs rough, your problem is not the thing you understand least, the distributor, it's something else you've done. To do proper diagnostics, put it on a scope. Don't have a scope? Take it to someone who can read simple instruction and knows how to tune an engine.

My 123 instructions say set the distributer advance at zero degrees. Also curve F has a 23.9 degree advance at 2000 rpm and 34 at 5000 rpm. Maybe the newer versions of 123 are setup differently.

Hi Y'all,

Progress...

I re-set the static timing to 12 degrees BTDC (from zero where my Prius mechanic had set it). This was the primary change, and made the Mini run much more smoothly. After a brief email (from Ed Madak at 123), I chose curve 'F' for now. Great engine response, no pinking, idles fine at 1000 rpm, etc..

The second issue is that my two-barrel Weber is gulping down lots more fuel than before the 123 upgrade, so I will have to attempt to tune it up a bit first, then revisit the advance curve issue.

Thanks again for all your insight and help. Very valuable and appreciated!

Rennie

p.s:
in the 123 manual and chart, there is a column with a header of 'Remarks', and for Advance Curve F it says: '2000/13.9'
This means that the advance is 13.9 degrees BTDC at 2000 rpm. 

I just found this website/page that has curve information for Minis.

https://123ignition.com/product/mini-4-r/

This page is for the non-vacuum version. Below the description is a link to the curve page. On it, you can try and look up the non-123 distributor you have and work back to find a possible curve.

My engine is similar to Kermy's A+  MG Metro 1275 with HIF44 etc. My 123 has vacuum advance. It is one of the earlier type where the curve selection switch is accessed through a hole in the bottom of the housing, so I can't say which curve I'm using. I wish I'd had Kermy's presence o mind to write it down! I understand in later versions the switch is accessed by removing the distributor cap.

If yours does have the vacuum advance port, it shouldn't matter - the vacuum advance is an economy device that allows the engine to run leaner on part throttle. I believe Cooper Ss didn't have vacuum advance, so it isn't surprising yours doesn't. If your pre-123 ignition worked well without vacuum advance, you shouldn't need it now.

When I bought mine, the recommendation was to experiment with various curves and your engine will tell you what it wants. You could start with a curve based on engine build and auxiliaries but your engine might like something different. That was the case with mine -  the best curve wasn't close to what he specs suggested. 

I wasn't really recommending position 4, in fact, I think I need more total advance along the lines of C,D,E or F.

Hi Kermy

Prior to the installation of the 123, my Mini started, idled, and ran fine in low rpm’s, so I assume that I can get it to do so again with the new dist..

thanks for the tip about setting #4 on the 123. This is what I was looking for. Now I will go out and:

1) check the static timing (thanks Dan)
2) check for a vacuum advance port (pretty sure it is not there/used, but…),
3) and change curve to #4.

I’ll let the forum know what happens. 

R.

The 123 distributor I have has vacuum advance, so yours could too. If it does there will be an inlet port nipple on the side. I think all 123 distributors come equipped with a vacuum port. I'm not sure what would happen if yours is not connected ... nothing really untoward I suspect.

My Mini has a 1275 Cooper S motor with a mild MG Metro cam and a SU HIF 44 carb. In my 123 instruction manual there is a penciled-in  arrow pointing at curve 4 which I assume is what I selected but it was many moons ago and I don't really remember. Your motor should run regardless of the advance curve you select but obviously will run the best with the correct curve. I'm also thinking you have a long duration cam that causes poor running at low rpm.  

Thanks Dan and 6464,

No vacuum advance (I understand Cooper S’s were not equipped with vacuum…).

I’ll try out the different curve settings. Good to know about the 500 rpm info!

Rennie

I would verify the "Static timing".

With a 123, static timing is 0 (zero) degrees with the engine not running but with the ignition on. When you try to start the engine, the advance curve is not initiated until 500 rpm. It stays on zero, which makes a reluctant engine much easier to start. Once the engine reaches 500 rpm, the curve turns on and you get the advance according to idle speed. The various curves are not much different at idle. They do vary mid-range and at the top end.

Look at the curve charts and see which curves will give you more or less mid-range advance. Try different ones to see if there is any improvement.

There should be at least one curve that would work well with your engine.

You did not mention if the 123 included vacuum advance. If not, it should not matter. If so, verify it is properly connected and is receiving vacuum from the correct source. That should be somewhere immediately after the throttle, so the 123 sees maximum vacuum with the throttle mostly closed.

By your description of parts, you have a high reving engine (cam & weber ). With that compression, I think your mechanic is optimistic with the HP. Cams are designed to allow high air to flow when the engine is spinning 3K or better. Your case 2.5K. They do not like anything lower. At lower or take off speeds, it is not sucking a high quantity of air to the ratio of gas that is being dumped in.

To get your mini rolling from a start, You're probably pumping the gas peddle and slowly release the clutch (riding the clutch). Weber carbs dump a lot of gas, good at high RPMs. These components are not good for street driving. You might want to start by removing the weber and put on twin SU's. If that doesn't work, remove the cam and put in something mild.

Of course, this are only my opinions. But I can speak with some authority because I once had a Spreen's built race engine. It was cammed and had a weber. I sold it.

I recently installed a new 123 distributor, and do not know which ‘advance curve’ to choose/use.  The vendor (although friendly, and nice) has not been able to help.

Question:
Which advance curve setting should I start with?

Thanks in advance,
Rennie

Here are some details about my engine:
1275cc (probably bored a bit, but don’t know)
#4 = 165psi
#3 = 170psi 
#2 = 170psi
#1 = 173psi
new Bosch Blue 3 ohm coil
new “Classic Mini Ultrik 8mm” spark plug ignition wire set
new NGK resistor type spark plugs
valves adjusted to spec for “Stage Two” head (had everything rebuilt by MiniMania mechanic many years ago, I do not know how to tell which cam I have… Mechanic said “about 100 hp”…)
new 123Ignition Pre-A+ 123DIST-A distributor - advance curve set to “D” (I think)
static timing set by my Prius mechanic ( !!! )
Weber DCOE40, fresh foam air filter
no headers 
Mini Mania standard exhaust
temperature stays about 185 after warm up
oil pressure about 60#
about 5000 miles since rebuild

starts easily/immediately when cold. Difficult to start after warm up. 
ran adequately before new 123 distributor, daily driver
runs great after new distributor, once it reaches 2500 rpm or so
engine dies from idle, changing Weber idle screw doesn’t help