Timing Light

[jollyroger]

Can anyone recommend a timing light?
I was looking at some second hand ones on on ebay and wasn't sure if much can go wrong with a second hand one apart from the bulb.

Would it be best buying new?

Rog

[bmcecosse]

Really no need for it - just get the engine running then swing the dizzy back and forth till you get the smoothest idle. If needing to set up from scratch - then a little 12volt test bulb (or a cheapy meter) will tell you when the points open.

[MarkyB]

I was going to warn you about the type that fit in the HT lead and give a pathetic light but looking on Ebay I didn't see any of that type.
I especially liked this one:
http://cgi.ebay.co.uk/TIMING-LIGHT-GUNS ... dZViewItem
It looks like what Dan Dare would use to time his space craft. I don't think the dwell meter would be much use as I've never been able to find what the reading should be for a Minor. Maybe someone here knows?

[Stig]

I don't think the dwell meter would be much use as I've never been able to find what the reading should be for a Minor. Maybe someone here knows?

About 55-60 degrees I think.

[Kevin]

As mentioned the inductive type is the one to go for and a fully working one from ebay shouldnt be a problem if the seller says its all OK.

[Alec]

Hello Roger,

I have to disagree with BMCE on the 'no need'. It is very useful to be able to set the timing for maximum advance. i.e. the setting at high revs which is in the specifications. With old cars and dubious history, distributors are often replaced with the wrong unit or the right unit with internal parts replaced or modified.

The unit I bought, (and I don't even remember the make as it was along time ago) has a voltage check facility (points condition, engine not running), dwell, rev counter and timing read off knob ( to set the timing reading against the TDC mark, as it is often easier that way being as the TDC pointer is the largest)

Alec

[jollyroger]

Thanks for all your comments folks. I'll have another look on ebay.

[bmcecosse]

Alec - the original engine specs were generated in the days of leaded petrol - not relevant now ! The 'pinking' test is the only real way to determine how much advance your engine needs at decent revs. This - combined with 'best idle' result gives a setting to suit most conditions. If the two settings are found to be horribly incompatible - then the advance curve inside the dizzy will need modifying - either by simply filing the stop (if more running advance is needed) - and/or by changing the springs which is well beyond anything that can be determined without a rolling road. In most cars the vacuum advance unit will be found to be either leaking or just seized up solid - unless it has been renewed in the last 5/10 years. They rarely last longer - and that has quite an affect on the engine performance and fuel economy.

[Alec]

Hello BMCE,

to expand on my post,

yes, road trial and error will give optimum timing for the petrol used but, unless you dismantle the distributor you will not know if the internals are right for the engine. The specification number on the side is a guide but the internals may well have been swapped anyway. So a check at above 3,000 rpm should ensure that the timing is not too far out from what maximum mechanical advance the engine should have. Over advance, as you know of course, is detrimental to both power and engine life.

The other point, especially if you have points, is that you can achieve your optimum timing by road testing then check with a strobe to see what it is. After that, the timing can be set to that figure with the strobe which should be easier.

Vacuum advance never works, even when new if you drive hard

Alec

[Peetee]

Vacuum advance never works, even when new if you drive hard

I'm curious, why's that?

[Alec]

Hello Peetee,

that was a bit of a tongue in cheek really, but basically there is no vacuum with the throttle wide open and so no vacuum advance.
It is purely a device to allow a leaner mixture at cruise as a lean mixture requires more advance, which gives a more economical engine.

Alec

[bmcecosse]

Indeed the vacuum does nothing at full throttle - but it IS normally in action at idle - when the engine first starts the timing will be say 5 degrees before but as soon as it fires up a vacuum is ctreated in the manifold and the vacuum unit pulls the timing forward slightly - and that's the setting that gives the smoothest idle. The vacuum then adjusts the timing in inverse relation to throttle position - but in doing so it noticeably 'brightens' the engine when you put your foot down. And of course aids eceonomy by puklling the timing forward when cruising on light throttle. To return to the idle position - if thje vacuum is not working then owners will turn the timing forwrad to get the best idle - but now there is a bit too much advance for cold starts (the engine may even kick against the starter) - and possibly too much advance at high revs leading to pinking and maybe even detonation. So - as Alec says - yes it can be a handy device for rechecking your timing onece you have established the best setting for your engine - but there is no point in 'blindly' setting the timing at say 5 degrees before just because it says so in a 50 year old manual ! And - the vacuum advance should always be disconnected when checking at idle or a very false reading will be given - that's IF the vac advance is actually doing anything. It should be checked out from time to time by sucking the pipe and watching the plate move in the dizzy.