123 Ignition curve

[Tomas_Norway]

What ignintion curve should be chosen on the 1-2-3 ignition?

My engine has been modified to 10:1 CR, 2" SU carbs, ported alu head and 278 deg cam. I use the same spark plugs as BJ-8 engines.

Before the modification I selected the curve most close to the original 1959 MK1 spec, and that worked fine.

But now it seems that the engine wants more advance at idle (at approx 15-18 deg@1000 rpm it runs faster/better), and that results in pinging under load.

Has anybody found an appropriate curve, and what spec is that engine?

The different curves can be found at: 123 Ignition curves

 

[Jerry]

I started with profile 8 but switched to B at the recomendation of some other listers. The car runs fine but I suspect a loss of power and poor milege at this setting (as compared to another Healey I own). I may go back to 8 or ?

Jerry
BJ8
BN4

 

[andrea]

Hi Thomas
I have bought one 123 distributor for my AH 100/6 engine -
and I follow with interest all post on the forum -my car and engine are at first step of restoration so I don't help you in any way -sorry
I need if possible some info:
Are your Tachometer mechanical?
Have you encountered some problems for the 123 setting?
Are you satisfied ab Quality and Performs?

Andrea
https://picasaweb.google.com/searunner44/RESTORATIONAUSTINHEALEY10061958?feat=directlink

 

[Tomas_Norway]

Update: I chose to use setting no.5, with 15deg@1000 rpm, hence 35 deg maximum advance. It seems to be working fine with no pinging, at least for my engine spec.

I guess more maximum advance can be chosen if you have a standard engine, where the advance at idle is less. 35 deg maximum advance is said to be the limit? Do any of the listers have any comments?

To answer your questions, Andrea:
- Yes, I have a mechanical tachometer
- No problems setting it up, but I recommend having a machine shop install the drive cog for the distributor shaft to ensure it is well aligned.
- No quality or performance issues so far after 3 years.

 

[red57]

Hi,

I don't know anything about the 1-2-3 distributor. However, Our motors sound similar. I drive mine on the street, but racing performance is what I'm after.... I am not a pro, just an enthusiast so don't take anything I say as gospel.

Mine is at a lower comp ration (9.5:1 so I can run pump gas), iron head with lots of massaging, pair of HD8s, headers, stock flat top pistons and a 283 degree cam - oh, and lots of balancing of things.

I run a Mallory Dual Point dist. (just last year installed a Pertronics unit). The Mallory is set to give max advance at 2800rpm. Over the years I, and some others I know, have tried different total advance settings and I have always found my best performance at 35-36 deg. I know one guy who has a lot hotter motor than mine said the last time he dynoed his motor they found 34 deg. was best power.

I have always been told the 36 is max - don't go any further or you may have high speed detonation.

I have never checked what my timing is at anything less than max advance, but I can say mine idles fine and has good drivability at all rpms.

After looking at the link you gave for advance curves, my thought is that #5 only shows 30 deg at 4500. So, if you set it at 35 max advance, you would theoretically have 15 deg or so at 1000. From the chart, I would be thinking of using the F curve - a little earlier and more advance (24 at 2000) and a max adv. of 36 at 4500.

Again, these are just thoughts and I suggest you consult with the shop that did the motor work and see what they have to say. I am tuning for performance and may not be getting the best gas mileage possible with my motor. I have not gotten around putting it on a rolling road.

Good luck,
Dave

 

[Jerry]

I read the installation curves again last weekend and move the setting back to 8. This puts the max curve at 34, and at 2000 rpm, it is 17 degrees. I have yet to test it till I get the door on the car fixed.

Jerry BJ8