123 ignition system Timing - using a timing gun

[inca]

Hi

I recently fitted a 123 electronic distributor and set the unit to advance no. 6. The car is running well but speaking to an e-type mechanic the other day he warned me that the 123 distributor should be on setting 0 (zero) as any other setting would be too advance and cause the cylinder heads to over heat.

Please can I have some advice on this and whether this should be a concern?

I got my old timing gun out to check the timing but I have a query regarding how to best do this.

In the manual for the timing gun it instructs me to connect the gun to the lead for cylinder no. 1 but in the type manual (Haynes chapter 4 section 10.1 page 108) it refers to the engine being timed at cylinder no. 6?

Please can I have some basic instructions on how I best go about this?

Many thanks

Mark

[christopher storey]

Mark : first of all, it does not matter whether you use no 1 or no 6 cylinder to time from, as the crankshaft is in the same position when either of these are at TDC . It is usually more convenient however to use the front ( no 6) cylinder as then the gun leads do not have to pass all the exhaust manifolds to reach the timing pointer which I am assuming is on the left hand side. If you in fact have the pointer underneath , then it is even more necessary to use the front cylinder

Secondly, advance. Always check this first with vacuum disconnected . The mechanical advance varies between cars . your 123 should be set so that if you have a 3.8 , the total advance ( including static) does not exceed about 34 degrees in the range of crankshaft rpm 3600 to say 4000 . If it is a 4.2, then the max advance at similar speeds should be no more than 29 to 31 degrees. On many of the 123s ( you do not say whether you have the Jaguar type or merely the generic 6 cylinder version) you will in fact have difficulty in getting too much "mechanical" advance , and as far as I know none of them give as much vacuum advance as the original capsules gave ( a further maximum addition of about 18 degrees of crankshaft advance )

[wagstefan]

Hello Mark, Christopher,

I just bought also a 123-ignition for my old lady as well and therefore am quite fresh in the theory about this distributer.

The advance setting is already implied in the distributer, so it is correct to adjust the distributer to 0? on the damper at front of the crankshaft. It will then have the right advance ignition of about 10? when firing (My JAG-version one is always preset at 10? advance between 500-1000 rpm).
If you have adjusted it to 10? at the damper, you are running your car with 20? static advance firing. So in addition to a certain program choosen, you might exceed 40? advance firing at e.g. 4000 rpm, which is a bit too high and might not be healthy anymore for your engine. At least if you drive the car a bit harder.

Regarding the vacuum unit, I was told that this applies mostly when you put your foot off the pedal (not fully). Then the vacuum will be max. and the advance will be increased significantly. However driving without this feature is also possible (many 123 are sold without any vacuum function) and just lead to a higher fuel consumption - there is no risk to damage your car without the vacuum adjustment.

I hope this will help you!

REgards

Stefan

[christopher storey]

The vacuum advance is important. It affects not only fuel consumption, making a difference in my experience of about 10 per cent, but equally importantly affects part throttle response significantly. You will find that with vac advance working correctly, the throttle reponse is significantly crisper, and given that perhaps 95% of all running with an E is done at part ( and frankly, light ) throttle openings , this is important

[mgcjag]

Hi All..To the best of my knowledge there are 3 versions of the 123 being used on E types, the 123 Tune that is programable via a lap top, the 123 Jag-6-R-V which should have its stattic timing initially set at 10deg BTDC(as per the instructions supplied with it) & the GB-6-R-V that should have the static set to TDC( as per the instruction leaflet). The stattic timing point attracts a lot of confusion on the 123 forum especially with the two units above both having different set points, but they should initially be set as per the instructions............Which setting on the selector switch is trial & error to best suit your car......but the info above supplied by Christopher as to checking with a strobe to not exeed max advance is vital. Steve

[wagstefan]

@christopher - regarding the vacuum influence, well I definitely will not disagree.
I have not installed my 123 yet but also invested the 10 additional Euros to have the vacuum unit at the distributer (you can have it without it as well). However, you would not damage your engine without vacuum advance attached.

Different to that is if you have too much advance, especially at high revs - and yes, I totally agree therefore to have this checked with a strobe. And if you want to do it right you might also check if the top point is really correctly reflected at the scale at the damper. Some have a slight deviation.

But I did not know, that the 123 GB 6 and the JAG are different in regard of the initial advance setting at low revs.....

Thanks for this information!

Regards

Stefan

[mgcjag]

Hi All.....Info for anyone fitting a 123....note that when initially setting the 123 to your timing mark a small green LED lights (this does not indicate when the spark plug will fire) it is just the start point & the electronics in the 123 will determine when to fire . Also when the car is not running the 123 cuts the 12v circuit to the coil (this can cause confusion when trying to check the electrical Cct, but it does mean that the ignition can be left on without fear of overheating the coil. If experiencing problems on installation ensure that the 123 body has a good earth if nesessary connect a seperate lead. Lastely if using a strobe note that the connector to the spark plug lead sometimes has a arrow to show what way arround it should be connected.(false readings if connected wrong).....Steve