No Timing marks on dampener

[markb427]

Hi
I am trying to set the timing on my series 1 4.2 engine and there is no markings on my dampener. Is there any other way to check and/or set the timing?

[cactusman]

I have the same issue. There is probably a way to mark the damper based on TDC of the front cylinder but I simply got mine running happily at idle and gradually advanced the ignition in small steps until when one presses the accelerator hard going up hill in fourth one starts to hear knocking. Then retard a fraction until no trace remains. Within reason of course, the more advanced the ignition the better the performance at high engine speed but too far and knocking is the result which is VERY bad for the engine long term.

Doubtless someone here will be able to provide better guidance.

[MarekH]

It's deceptively difficult to find TDC directly on a cylinder because the piston is moving very little around TDC per degree of crank rotation. A better method is to measure a "fixed stop" position somewhere ~180' away, i.e. where the piston is moving the most per degree of crank rotation, both on the upstroke and then on the downstroke and TDC is halfway between those two marks (.

There is plenty of guidance online as to how to do that correctly.

You can then use a timing light in the conventional way.

kind regards
Marek

[markb427]

Thanks I'll do a bit more searching the posts thank you both

[christopher storey]

I think Marek means 90 degrees away from TDC when there is maximum movement/rotation ratio . I am very surprised that there are no markings at all, although they may not be where you expect them to be because at different times Jaguar put the marks to be read against a pointer at the base of the rotation next to the sump , and at other times against a pointer on the left side of the engine timing cover , which was much easier to read

[MarekH]

Yes I did mean to say 90'. Thank you.
A spread of +90' to 90' on the damper likely lead to the most accurate result.

Once you start reading around the topic, you'll also realise that cylinders move in oppositre directions as complimentary pairs. There is lots of fun to be had with geometry.

kind regards
Marek

[AussieEtype]

This vid explains how to find TDC on a V8 with No-1 cylinder is the relevant cylinder.

Same basic principle for a Jag 6 but I understand you use cylinder no 6.


I recently did this with my Rover V8 with my home made piston stop tool.


Garry

[MarekH]

Setting the timing "by ear" and then pulling it back a bit may or may not be a bad thing but it may not give the desired result across the whole rev range.

The total amount of advance is made up of two components typically:- mechanical advance and vacuum advance. It isn't obvious from the simple test under load that both are working as they should.

With the vacuum line plugged, you should be able to plot rpm versus advance using the timing light to see whether the distributor delivers the correct mechanical advance. When looking at the textbook, remember the distributor turns only once per every two full rotations of the crank - distributor rpm is half that of crank rpm.

When there is a kink in the mechanical graph, this is because the two springs/weights in the distributor are of uneven length or strength. This is deliberate, so that the mechanical advance increases rapidly at low rpm (pulling the "easy" spring") and then incrreaes only slowly around and after the point of maximum torque (the heavier duty longer spring takes over).

You can then retest the advance with added vacuum.

Given the amount of Megajolt ignition data on another thread showing you a complete map, you can easily do better than just a single point test.

Manufacturers will have set the settings at a conservative level because they do not know what quality of fuel may be subsequently put into the car and the simple test may mean you get caught out by this.

kind regards
Marek