Wandering Timing Magical Mystery!

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Major_Tom
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Wandering Timing Magical Mystery!

Post by Major_Tom »

..here's a funny one for you. I can't understand this at all.

My ignition timing wanders. Over 3000 - 6000 odd miles, it creeps from 8 btdc to the point it wont start at around 12 - 14 degrees btdc!

Everything is tight.

New distributor.

New auxiliary shaft.

It was doing this before the new parts too. It's really weird as I can't see how this can happen. Has anyone ever had or heard of anything like this?
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Re: Wandering Timing Magical Mystery!

Post by [email protected] »

Yeah, that is unusual :shock:

Just to check..Are you timing it and checking it with the vacuum advance removed? It will move under vacuum as normal so would give different readings when checked.

If it’s changing and the distributor body is tight (and it’s drive gear is correct) then thinking about everything that might jiggle the timing all I can think is either, the cam belt is stretching over time changing the timing (don’t see how but that would move the timing) one of the cam toothed pulleys is moving independent of the actual cam belt (again, they shouldn’t but…) or that the internal plate that allows vacuum advance/retard to move is loose in some way so it’s flopping about and changing the timing?

Other than that I don’t see how the timing can move? And since it was doing it before new parts it makes it even more of a magical mystery to be sure!
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Re: Wandering Timing Magical Mystery!

Post by pbar »

As with the previous reply, I'm also thinking of something odd with the timing belt Tom. Is that new also? If not it may be worth changing it as they're cheap enough.
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Re: Wandering Timing Magical Mystery!

Post by Mc Tool »

End float on th aux shaft ? If it was able to move in and out it would alter spark timing . Im assuming cam timing is constant. 6 deg aint much ....enough to cause starting issues , specially if there is a bit more compression than usual . Its just about gotta be somewhere around the aux shaft or dizzy drive gears .
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Re: Wandering Timing Magical Mystery!

Post by Mr B »

Major_Tom wrote: Sat Jan 15, 2022 12:48 pm ..here's a funny one for you. I can't understand this at all.

My ignition timing wanders. Over 3000 - 6000 odd miles, it creeps from 8 btdc to the point it wont start at around 12 - 14 degrees btdc!

Everything is tight.

New distributor.

New auxiliary shaft.

It was doing this before the new parts too. It's really weird as I can't see how this can happen. Has anyone ever had or heard of anything like this?
Points and condenser or leccy ignition?
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Re: Wandering Timing Magical Mystery!

Post by Bug »

How tight is the belt tensioner?
I had one once where the numpty before me had levered the tensioner as tight as they could, rather than letting it settle into a natural position.
It held the belt tight against the top pulley for too long and gradually would lift the belt out of the tooth and into the next one.
Given my assumption that you still have your tendency to utilise the full rev range ( ;) ) it may be that the belt is slipping?
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Re: Wandering Timing Magical Mystery!

Post by Supercharged Nat »

Check the dizzy end float too, they are not supposed to have much but ive seen them with 2mm or so
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Re: Wandering Timing Magical Mystery!

Post by Mc Tool »

I have a book here called "Pinto , the worst engine ever made" ,this sort of thing is probly just one of the reasons . :poke: :poke: :xd:
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Re: Wandering Timing Magical Mystery!

Post by Major_Tom »

Thanks gents, will report back when I can!
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Re: Wandering Timing Magical Mystery!

Post by Bug »

Major_Tom wrote: Mon Jan 17, 2022 1:34 pm Thanks gents, will report back when I can!
If you remove the belt cover (if you have one?) then slowly turn the bottom pulley using a suitable socket you may be able to see the belt riding up the top of the cam sprocket then falling back again. That's how I found mine.
That was on a GT4, wonder if there's any of those left now?
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Re: Wandering Timing Magical Mystery!

Post by Major_Tom »

Bug wrote: Mon Jan 17, 2022 5:04 pm
Major_Tom wrote: Mon Jan 17, 2022 1:34 pm Thanks gents, will report back when I can!
If you remove the belt cover (if you have one?) then slowly turn the bottom pulley using a suitable socket you may be able to see the belt riding up the top of the cam sprocket then falling back again. That's how I found mine.
That was on a GT4, wonder if there's any of those left now?
I am thinking of a respray and adding the side decals from the GT4 actually, they look so fantastically 80s, I love it.
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Re: Wandering Timing Magical Mystery!

Post by Bug »

Major_Tom wrote: Tue Jan 18, 2022 11:12 am
Bug wrote: Mon Jan 17, 2022 5:04 pm
Major_Tom wrote: Mon Jan 17, 2022 1:34 pm Thanks gents, will report back when I can!
If you remove the belt cover (if you have one?) then slowly turn the bottom pulley using a suitable socket you may be able to see the belt riding up the top of the cam sprocket then falling back again. That's how I found mine.
That was on a GT4, wonder if there's any of those left now?
I am thinking of a respray and adding the side decals from the GT4 actually, they look so fantastically 80s, I love it.
Don't forget the bonnet ones too.
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