123 Tune Bluetooth curves

[Pianoman]

I just fitted the a new distributer with bluetooth and I am very impressed but am wondering what curves are recommended for the 4.2 engine or can they be downloaded?

[rswaffie]

There are a number of posts on the forum related to 123 settings - try this for starters...

viewtopic.php?f=3&t=15407&p=125978&hili ... th#p125978

[Tom W]

If your engine is standard, I’d copy the appropriate curve from the factory workshop manual and start from there. The shape of the curves vary between SU and Stromberg equipped cars, and the advance values are different depending on compression ratio. The workshop manual gives an upper and lower limit for an acceptable distributor curve. I expect the upper limit is a safe maximum before pinking occurs (on 1960s petrol) and the lower limit still gave acceptable performance. I’d probably start with the median values. From there, I’d go for a drive and see how it performs.

[christopher storey]

The first rule is choose a curve that does not exceed max advance ( mechanical + static ) of 34 BTDC. The second thing to consider is that these engines if they are going to pink, commonly pink in the 1800 - 2500 rpm (crankshaft speed ) range, and so you want to choose a curve that does not have too steep an initial advance curve . The original distributor curves are all given in the Electrical Section , section P , of the Workshop Manual , in the Knowledge base on this site. Bear in mind that the rpm figures are distributor speed i.e half crank speed , and that these settings were for 5 star fuel. I suggest that a setting which keeps the standard 9 degs BTCD static but uses a total setting about 2 degs less than those shown in the book at the relevant speeds would be a suitable starting point. If the engine fluffs under acceleration ,( with the vac advance also connected ) then try advancing the curve 1 degree at a time . Bear in mind that your engine will lose very little power by being a degree or two retarded, but will suffer both power loss and the potential for harm by being over advanced

[Pianoman]

thanks everyone.... I think I'll have to get someone locally who understands it better than me in case I mess up something

[christopher storey]

Piano man : one vital bit of information which I forgot to include in my previous post is that the workshop manual figures for degrees of advance are also distributor degrees. So, the crank advance is twice the amount shown in the manual . So , e.g. at 800 dist rpm ( crank 1600 rpm ) the dist advance should be between 5 and 7 degrees, and the crank advance should be between 10 and 14 degrees, plus the static advance of 9 degrees = on a timing light at 1600 rpm somewhere between 19 and 23 degs BTDC

[max-it-out]

Easy to measure degrees on the crank , using the marks on the CSD ( assuming the pointer truly reflects the position of the pistons ) , but ...is there an easy way to measure degrees of movement by the distributor ( disclaimer - I am a novice mechanic , so accept this may be a silly question )

[mgcjag]

Hi Mark...what is CSD?...small movements of the distributor can be fairly acuratly made useing the vernier adjuster...Steve

[christopher storey]

Mark : if you are meaning is there a way to measure the advance in distributor degrees, ( as given in the manual ) the answer is no . Such measurement requires a specialised distributor setup machine . Whilst such machines were installed at various specialised auto-electrical workshops in the 1940s to 1950s, they started to die out once things like the Suntester became widely available , and became completely superseded when electronic ignition came along

[Tom W]

Crankshaft damper, I presume.

Measuring degrees of movement on the distributor as fitted to the engine is pointless. What’s measured on the damper is what’s actually happening on the engine, and that’s what’s important. It takes into account any wear in the distributor drive, which you wouldn’t measure at the distributor.

The reason the workshop manual quotes distributor degrees is because that’s for testing the distributor curve on a distributor test machine, remote from the engine.

[max-it-out]

Hi Mark...what is CSD?...small movements of the distributor can be fairly acuratly made useing the vernier adjuster...Steve

re. the Vernier adjuster - that`s the reason I wanted to measure degrees at the distributor . My car ( ex-US ) still has it`s emission dist. the curve of which is different to the standard unit , so , I thought I would try to use the Vernier adjuster to advance the timing a bit so it more closely matched that produced by the standard unit , possibly with a bit more to simulate the extra advance given by the vac. unit ( not on mine ).

So I needed to know how much a " click " represented in degrees on the dist.

The ( very rough ) measurements I did showed that the total adjustment capacity of the Vernier adjuster was 18 degrees ( 9 degrees either side of the central position ) which represented 140 clicks ( 280 in total ).
With this info. I was able to advance the dist. by 70 clicks ( 4.5 degrees dist ) which represented 9 degrees on the CSD .
Hopefully this will give better responsiveness and fuel economy , although , having looked at the advance curve , I might have to keep it below 4000 rpm due to excessive advance at higher revs ( that's the fault of the emissions dist. ).

A better solution would be a new standard dist. or a 123 type with vac . advance -

[Tom W]

Hi Mark...what is CSD?...small movements of the distributor can be fairly acuratly made useing the vernier adjuster...Steve

re. the Vernier adjuster - that`s the reason I wanted to measure degrees at the distributor . My car ( ex-US ) still has it`s emission dist. the curve of which is different to the standard unit , so , I thought I would try to use the Vernier adjuster to advance the timing a bit so it more closely matched that produced by the standard unit , possibly with a bit more to simulate the extra advance given by the vac. unit ( not on mine ).

So I needed to know how much a " click " represented in degrees on the dist.

The ( very rough ) measurements I did showed that the total adjustment capacity of the Vernier adjuster was 18 degrees ( 9 degrees either side of the central position ) which represented 140 clicks ( 280 in total ).
With this info. I was able to advance the dist. by 70 clicks ( 4.5 degrees dist ) which represented 9 degrees on the CSD .
Hopefully this will give better responsiveness and fuel economy , although , having looked at the advance curve , I might have to keep it below 4000 rpm due to excessive advance at higher revs ( that's the fault of the emissions dist. ).

A better solution would be a new standard dist. or a 123 type with vac . advance -

That sounds very risky. Vacuum advance is only there for low load, part throttle scenarios. You shouldn’t add mechanical advance to compensate for not having vacuum advance. If you plot the distributor curves for both US and non US spec engines, you’ll find they’re different. As the only adjustment you can make on the car is to change the “height” of the curve, the best you can hope for is to pull the US curve up or down until it meets the non US curve at one point. The rest of it will either be under or over advanced, depending on the relative shape of the curves. Neither is desirable, but under advanced is preferable.

Have you done anything else to the engine, either changed the fuelling, or replaced the carburettors?

If you still do want to move the curve you have, you don’t need to work out how many degrees one click equates to. Just measure the timing you have at idle, and adjust it until you’ve added however many degrees you want to add on. The whole curve will move up by that amount.

[max-it-out]

Thanks , yes , I appreciate that . Unfortunately , I can`t get under the car to set the timing using the marks on the CSD , so using the dist. Vernier is a lot easier.

[Tom W]

How do you know what your baseline timing is set to if you can’t check the timing with a timing light?

[max-it-out]

Good point - The PO had written on the air cleaner that IT should be 5 degrees BTDC so I just assumed that was correct