[Healeys] Spark Scatter over 4000rpm

[Oudesluys]

Andy,

Replace the no. 1 spark plug lead using a copper core lead and a 
standard non resistor cap and try again. Also make sure the pick up 
clamp is clean, intact and closed properly
If it still shows the deviations you describe and if the engine runs 
smooth at the given rpm it may well be the Hella Optilux. Although it is 
an excellent timing light it could be rather old by now and may not work 
properly any more. These were first made over 30 years ago. During the 
years the design has had little change.

Kees Oudesluijs


Andy Thorp schreef op 25-2-2014 11:33:
> I'm having an issue with timing mark jumping around on a BN4 engine at high
> rpm and I can't decided whether it is due to a dodgy timing light or something
> internal. The mark jumps around maybe +/- 10 degrees randomly over approx
> 4000rpm but is otherwise steady at lower speeds. I removed the advance weights
> entirely and locked the upper spindle to the main shaft as well as locking the
> vac advance plate but no change to the behaviour.
>
> The distributor is original Lucas with Pertronix +ve earth module. There is a
> tiny bit of slack in the shaft if I disassemble it and wash out all the grease
> but it is not noticeable when greased so I'm thinking that should not be the
> cause of the issue. There is the normal amount of rotational slack from the
> drive dogs and bevel gear. Checking on an oscilloscope didn't show more than
> 500us difference in switching events and had no change when the timing mark
> jumps around. The rest of the ignition system is stock except for NGK 5k ohm
> resistor spark plug caps.
>
> Timing light is Optilux which is by all accounts a reputable brand although it
> does show a similar thing on another engine but nowhere near as bad.
>
> Engine is fairly stock Longbridge with 10:1cr and about 2000 miles since a
> full rebuild
>
> Anyone else experienced this?
>
> Andy.
> _______________________________________________
> Support Team.Net http://www.team.net/donate.html
> Suggested annual donation  $12.75
> Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
>
> Healeys at autox.team.net
> http://autox.team.net/mailman/listinfo/healeys
>
> Unsubscribe/Manage: http://autox.team.net/mailman/options/healeys/coudesluijs@chello.nl
>
>
>
> -----
> Geen virus gevonden in dit bericht.
> Gecontroleerd door AVG - www.avg.com
> Versie: 2014.0.4335 / Virusdatabase: 3705/7123 - datum van uitgifte: 02/24/14