Dynamic timing for positive earth

[Cam]

Anyone tried dynamic (stroboscopic) timing for positive earth cars?

Can the guns cope this way round??

I suppose the inductive pick-up ones would be OK, but my Gunsons one (with the spring pickup) might be wired directly internally and might not like it.

I don't fancy taking the gun apart to find out. I just wondered if anyone has tried this?

[57traveller]

You've sown a seed of doubt now Cam I've recently purchased a Gunson "Timestrobe" to replace my ailing and ancient original timing light that just connected in series to no. 1 h.t. lead and used to work fine on both +ve and -ve earthed vehicles.
The Timestrobe, which I haven't used yet has an inductive pickup which clips over no. 1 h.t. lead and is powered from the battery, hopefully this is the type you think should be o.k. The instructions just state that the power supply connections, red and black, should be connected to their respective battery terminals. There is no warning of polarity sensitivity. I assume this must be different to the type you have (spring pickup). It will be interesting to learn if anyone has used either or both types.

[Cam]

57,
Right! Mine (that I was worried about) is the spring type than connects 'in series' with the HT lead and the plug. So your old one was this type then, if so mine should be OK as you say it works fine on both +ve and -ve vehicles.

The timestrobe should be fine with an inductive pickup as it is DC decoupled from the earth supply, so polarity of earth should make no difference as it's only the AC current spike that it detects.

[57traveller]

Good, that's cleared that up then! Just a bit of confusion as to what you meant by "spring" type. So you should be o.k. I think the old one of mine is Gunsons and it's done sterling service over many years with BOTH polarities as I said. Does yours have the extra cables for connecting to starter solenoid to enable the engine to be "inched" over with the timing light? Obviously won't work on the earlier Minors with pull type starter which connects power directly to the motor. There's more insulating tape on the leads now than original, aren't those continuosly running cooling fans a pain?

I'll just make sure I hide if yours blows up now

[Cam]

No, mine just has the 3 cables. One for +, one for - and one with the spring on the end for connecting in-between the plug and HT lead. It's the 2nd one I bought and I bought it years ago. The previous one was exactly the same but it was abused a lot and just fell to bits eventually.

Yes the yellow steel cutting blades at the front of the engine can be a pain!

[57traveller]

Mine must have been a "posh" one in it's day then. (early 70's)

[Kevin]

Yes the yellow steel cutting blades at the front of the engine can be a pain!

Well thats am apt description Ive not heard before

[rayofleamington]

those continuosly running cooling fans a pain?

been there done that... My battery charger wires have a fair bit of tape on them ;-)
For 'lightening' the HT leads, my favourite was the dynamo fan blades

[57traveller]

Even the body of this old timing light is scarred and gouged as a result of being assaulted by fan blades where it could easily have been fingers or hands bearing the scars. We do some stupid things at times.
Could be an explanation of my 17 degrees timing advance some months ago. I blame failing eyesight though. A big minus for these older timing lights is the need for almost total darkness in order to see the damn illumunated marks.

[Kevin]

A big minus for these older timing lights is the need for almost total darkness in order to see the damn illumunated marks.

I agree with that 57 and I used to use an old blanket to help until one windy day