Timing problem

[richardy8496]

Having just rebuilt the head, I am now having trouble with the ignition timing, in particular the position of the distributor, which I foolishly removed. Does anyone know if the spark is generated when the contact points open or close?

[JonB]

The points close, the distributor charges, the points open and that is when the spark is generated.

[richardy8496]

Thanks for that. The other concern is that the distributor maybe 180 degrees out. Is there any way of checking No 1 is TDC on the firing stroke without taking the cam cover off again?

[p.faurie]

Remove the plugs,put your thumb over no1 plug hole,turn engine over by crank pulley you should be able to feel compression on compression stroke, check tdc with a screwdriver down plug hole/crank marks,check rotor is at corresponding plug lead segment in cap,if not move dizzy or swop over plug leads,hope this helps
Phil

[sprintsoft]

Hi Richard,

It’s quite easy to sort out, line up your pulley tdc mark to tdc on the front cover, open the oil filler cap on the cam cover and you can check the camshaft lobe for nr 4 exhaust.

If you are at tdc for nr 1 cylinder, the nr 4 lobe will be pointing in towards the spark plugs, in that case job done, however if nr 4 lobe is pointing away from the plugs and out towards the side of the car then rotate the crankshaft 360 degrees to bring nr 1 to the top of its compression stroke.

Ease the crankshaft back to the 10 btdc mark, then rotate your distributor clockwise to just begin to break contact for nr 1 cylinder. That position should get the engine started. If you do this carefully you will find the timing can be very close to spot on when you put the timing light on it.

**You can use 12 btdc if on Weber’s and a big valve motor.

Regards
Iain

[alan.barker]

Before you put the dissy back fit new Points and adjust gap. When you turn back to 12degrees turn back more, then slowly turn Crankshaft in clockwise direction to line up at 12degrees.
Be sure the Clamp on the Dissy is located fully on the machined shoulder or you will damage the Dissy.
Alan

[JonB]

Definitely do the gap with the distributor out. Better still, use dwell angle, which is the period the gap is closed in rotational degrees of the distributor shaft (read up on dwell angle, it is very interesting).

So... when I did mine I put a lamp across the coil inputs and turned the engine by hand. I could see where the points opened and closed, and with reference to the timing marks on the front of the engine it was pretty easy to approximate the setting. Imagine my surprise when I found it was bang on 12 degrees BTDC after starting the engine with a timing light.

As to locating TDC without the cover off, do as already suggested. Pull all the spark plugs out and turn the engine until you feel compression in cylinder 1, then continue turning until either a) the timing mark on the pulley points to the zero mark on the casing and / or b) the piston in no.1 is at its highest position (I used a screwdriver sticking out of the spark plug hole to see this, roughly).

Once you start doing it you'll find it remarkably easy. Remember you can turn the engine backwards if you overshoot the points open position.

[edit: Sorry, this is the same as what sprintsoft is saying..]

[Andy8421]

With reference to a couple of the suggestions above, it isn't a good idea to turn the engine 'backwards' to align the timing mark, as this takes up all the lash between the crank and distributor the wrong way. If you do go backwards, go a long way backwards, then go forwards to the timing mark. The takes up the lash in the sprocket, chain, jackshaft, skewgear and distributor in the same direction as when the engine is running and results in a much more accurate setting. Doesn't really matter if all you are doing is trying to get it to start to then use a timing light, but it does matter if this is the only way you time the engine.

[alan.barker]

Yes exact,
take it a long way backwards then turn clockwise to take up slack and approach 12 degrees slowly.
Alan

[JonB]

Good point chaps..!

[richardy8496]

Thanks, everyone - all very helpful.

[HCA]

Or, save yourselves a lot of grief and fit an EDIS..

- I'll get my coat on the way out

[richardy8496]

I've got it going at last but am now considering changing the distributor for an electronic one as, judging by the bundle of historical invoices I have, the car seems to eat contact points and condensers. I was recommended 123 as the best but I can't see that they do a model to fit the twin cam with positive earth. Which one did you use?

[alan.barker]

You can buy from "Distributor Doctor" a new Points Base Plate so you can fit Cooper "S" heavy duty points + Condenser to match. Problem solved
Alan

[sprintsoft]

+1 for Distributor Doctor...

I also have lots invoices for points and condensers, that just means I changed them often as they’re so cheap - precautionary measure!

Aldon Automotive can supply a new distributor with electronic ignition built in if you want to go that way.

Iain