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Uneven Timing light


Adrian
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Hi all

Prior to the carb issue I put the timing light on cylinder 1 and got an uneven 'flash'. It's perhaps not much but wondered if it pointed to and issue with the HT leads or distributor?

Not much in the way of sideways movement on the shaft. No carbon / burning on the cap - looks almost new.

Or could it be associated with the mixture being too rich.

Adrian

PS also wondered about converting to electronic ignition - what would you do - new distributor or just but a conversion kit and if so which one?

 

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It looks like it's randomly failing to spark. Try it on the other plugs to see if it's just number one. Then you'll have a better idea if it's HT plug leads or something else. The mixture might cause problems with combustion, but not the spark.

Electronic Ignition is a good upgrade and generally done to the existing distributor, you don't want to be changing the dizzy for no reason! A 72 GT6 will be a ballasted system and some of the cheaper EIs don't like it. I have and Aldon which said on the box "For 6volt ballasted system". Unfortunately now eye wateringly expensive, £100+.  There are cheaper ones, around £30 on Fleabay, but some have a poor reputation.  

Some people revert to the 12volt system for which there's a bigger selection of EIs.  However this requires a different coil and a little rewiring, bypassing the resistive ballast wire.

Doug

 

 

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A lot of the randomness in that video is fake. It's an artefact of the interaction between the timing of the (very short) strobe flash and the timing of the video frame capture.

Does the engine idle rough? If it's actually failing to spark then you'd hear it. If the spark is occasionally a little weak, the strobe may not notice it (it's looking for a spike in the current in the plug lead, and isn't very sensitive). For that matter, some strobe lights are a bit erratic on whether they see the next spark when they're a little way apart, like at idle.

Electronic ignition may help make the spark big enough for your timing light. That may not necessarily do anything for your engine running, though it shouldn't make anything worse.

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2 hours ago, Adrian said:

Hi all

Prior to the carb issue I put the timing light on cylinder 1 and got an uneven 'flash'. It's perhaps not much but wondered if it pointed to and issue with the HT leads or distributor?

Not much in the way of sideways movement on the shaft. No carbon / burning on the cap - looks almost new.

Or could it be associated with the mixture being too rich.

Adrian

PS also wondered about converting to electronic ignition - what would you do - new distributor or just but a conversion kit and if so which one?

I think the strobe should light up at same timing mark on number 4 as on 1 then. If the dizzy shaft doesnt have much play I cant see anything else wrong with it would explain the erratic idle sparking (that doesnt discount the points, cap and leads etc) so dont think you should replace it or get electronic ignition yet. I would sort this issue out first before introducing more variables. Fuel mixture will of course cause poor running but the spark should still be pretty regular because the crank and flywheel have a lot of inertia that help to smooth out any misfires.

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is this related to the plug fouling syndrome  we have been debating , yes 1 and 4 gives the same optical result for tdc markings

have tried reverse the ht clip over ??

the dizzy looks ok that lift is normal  make sure the cap has a brush in its centre and a red rotor on lucas is advisable 

 

Pete

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Just ran it on all 4 leads. Btw already running much better now the jet is sitting flush!

 It seems to be very even on 2 and 4 but jumps about a bit on 1 and 3. I do agree the gun doesn’t seem to pick up all the time as I revisited a lead and got a different result. It’s running at about 7 degrees and should be at 5 so again may contribute. As it’s not on all 4 my novice head says probably leads or cap?

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I have new plugs but was waiting to get it tuned to limit carbon fouling. I tried the gun again and it was ok on all this time. Audibly there is a very slight occasional stumble but it ticks over. Can’t take it for a run yet as need to sort an mot first.

perhaps it is the spark strength / sensitivity of the pick up.

on a slightly different note - the guide for a stage 1 kit says 8 degrees but I’ve seen people online do 30 odd degrees at high revs to get full advance (Stevenson’s garage, or something like that. Quite a good series of guides)

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Pretty much all normal engines of the day would have a dizzy max of 28 to 32 at the crank at 3000rpm  vac  off.

The higher the state of tune or Improved efficiency in the burn needs less advavance as the bang goes off quicker 

Many  wsm give dizzy test data and  its always tests  decelerating   bear this in mind when checking timing 

Pete

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