Ignition Timing Which Cylinder? Mk2 3.8

[344739lv]

Hi all, can anyone help. I am a about to check my ignition timing on a 1961 Jaguar Mk 2 3.8. The Timing Light Instructions advise me to use Cylinder Number 1 - which they say is at the front of the car.

I have always understood that Jaguar count from the back of the engine forward - Hence Number 1 would be at the bulkhead end and number 6 at the front.

The leads on my timing light are too short to reach all the way around the engine bay and down from the bulkhead cylinder.

So my questions are:

1) Am i correct about the cylinder positions?
2) Can I connect the light to the front cylinder and if so does this affect the reading in any way?
3) If all else fails - is there a good timing light with LONG leads on the market - although this is less preferrable as I have a perfectly good unit.

Any help would be much appreciated.

Tim

[piman]

Hello Tim,

1) Yes.
2) You can and it should give the same result.
3) You don't need to attach to the plug end of the lead, just connect at the distributor (I'm assuming a clip on H.T. sensor). If it connects directly at the plug then time on number 6 cylinder.
Otherwise there is no reason you can't extend the lead with a length of H.T. lead if you wish.

Don't assume correct timing by a strobe alone, road test and if it doesn't pink, using the distributor vernier, advance in small increments until it does then back off a bit so it doesn't. This give the best setting. While you have the strobe on, check that the timing advances to full advance by revving the engine above 3,500 rpm, this should be around 45 degrees BTDC. (Vacuum advance pipe disconnected)

Alec

[344739lv]

Alec,

Top man - many thanks for your help on this.........good shout on connecting at the distributor end.......I am too thick to think of that.

Best Regards

Tim

[344739lv]

All,

I finally got around to looking at the timing on my 3.8 following the instructions from Alec in the thread with this post. After warming the engine and disconnecting the vacuum advance, my timing is showing OFF THE SCALE on my timing gun. Even when dialling in 60 degrees of advance, the 0 degree marker on the pully is a mile off. Basically if you think of the pointer at the bottom as the number 6 on a clock face, the timing mark on the pully shows 3 with 60 degrees dialled in!

I have set it by ear, and it now shows 4 on the clock with 60 degrees dialled in.

It seems to run ok - but clearly I haven't got a clue what the true timing is and I must be doing something wrong.

If I dial out the advance on the gun, by the way, the mark disappears back up around the clock somewhere and comes around toward the mark the more you advance it on the gun.

Any help appreciated.

Tim

[cstorey]

The first thing to do is to check whether the marks on the pulley show TDC when the engine is in fact at TDC . The most accurate way to do this is with a dial gauge stuck in the front plug hole, but you can get a good idea whether there is some gross discrepancy in the markings by using a metal bar, or for that matter a wooden stick, and putting it in the hole and then turning the engine by hand, or by pushing it in gear until the bar/stick rises to its uppermost position . The reason for this check is that it is not unknown for the rubber on the crank damper to deteriorate to the extent that the damper inner and outer parts rotate relative to each other, and it is certainly a possibility given the symptoms you describe . If the markings are anything like accurate, then the next thing to do is to static time the engine, using either a voltmeter on the distributor low tension circuit , or a 12 volt bulb, so as to see when the points open. This should be at about 9 degrees before TDC . Once you have that basic setting sorted, then you can revert to your strobe

[344739lv]

Really helpful - many thanks. As it turns out, when the engine was rebuilt the garage changed the pully to a later type and installed a new timing pointer on the left of the engine under the alternator. It times to this mark perfectly.

Tim