Timing - Symptoms

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myoldjalopy
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Timing - Symptoms

Postby myoldjalopy » Tue Jul 05, 2016 10:32 am

Hi, here is one for the 'experts', just out of interest really.
What symptoms would you expect if you progressively advanced the timing, and what symptoms would you expect if you progressively retarded the timing?
Cheers,
Pete

amgrave
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Re: Timing - Symptoms

Postby amgrave » Tue Jul 05, 2016 11:17 am

At tick-over if you advance the engine will slow down, if retard will speed up. You want a happy medium between them and then test on a hard run to listen for pinking under acceleration. From personal experience I have found the timing ends up a few degrees more retarded than the original settings.


myoldjalopy
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Re: Timing - Symptoms

Postby myoldjalopy » Tue Jul 05, 2016 1:28 pm

OK, that's at tickover. What might you notice on a run?

amgrave
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Re: Timing - Symptoms

Postby amgrave » Tue Jul 05, 2016 1:53 pm

More or less power depending on where the timing was in the first place before altering it, but it is sometimes very subtle and hard to notice and any change in engine note can be lost in the general noise. It all depends on how far out it was in the first place. I've already mentioned pinking. By the way I'm not an expert :lol: :lol: :lol:


bmcecosse
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Re: Timing - Symptoms

Postby bmcecosse » Tue Jul 05, 2016 10:28 pm

Pinking / detonation with ruined pistons/valves if you run too advanced. And it will kick against the starter if the static timing is advanced beyond about 5 degrees.
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myoldjalopy
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Re: Timing - Symptoms

Postby myoldjalopy » Wed Jul 06, 2016 11:32 am

And if too retarded? What running symptoms then?

amgrave
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Re: Timing - Symptoms

Postby amgrave » Wed Jul 06, 2016 1:08 pm

Lack of power but no noticeable change in note.


simmitc
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Re: Timing - Symptoms

Postby simmitc » Wed Jul 06, 2016 1:56 pm

Starting might be more difficult if too far retarded. The piston has passed TDC and is on its way down, meaning that (assuming that there is still enough compression for it to fire) the explosion is less effective and you might not get sufficient power to keep it running. This is obviously in extreme cases.

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Re: Timing - Symptoms

Postby bmcecosse » Wed Jul 06, 2016 7:56 pm

It will always start 'retarded' (within reason) - but may run so hot the exhaust manifold can glow red! It's so easy to get it right - don't worry about it being wrong..... Of course -check the vac advance is working as it should, and the mech advance.
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myoldjalopy
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Re: Timing - Symptoms

Postby myoldjalopy » Wed Jul 06, 2016 8:21 pm

Thank you for your replies. In summary I conclude:

Too retarded - will cause lack of power, poor fuel economy, backfiring, and poor performance including starting.
Too advanced - will cause hard starting, kicking back on being started and pinking (pre-ignition)

It is useful to know these things.......................

bmcecosse
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Re: Timing - Symptoms

Postby bmcecosse » Thu Jul 07, 2016 5:52 pm

It will start - Veteran cars have a lever specifically to retard the ignition timing for starting. as alrady stated -check the vac advance (suck the pipe) and the mech advance (twist the rotor) before worrying about anything else.
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myoldjalopy
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Re: Timing - Symptoms

Postby myoldjalopy » Thu Jul 07, 2016 8:20 pm

Hello Roy. I'm not worrying about anything, the car is running fine. I was just curious - the more you understand how these cars operate, the better prepared you are if something goes wrong 8)

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Re: Timing - Symptoms

Postby bmcecosse » Thu Jul 07, 2016 9:33 pm

Or you just have more to worry about..... :lol: :lol: :lol:
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Re: Timing - Symptoms

Postby IslipMinor » Fri Jul 08, 2016 1:15 am

it will kick against the starter if the static timing is advanced beyond about 5 degrees
Roy, You've made this statement before, and I still disagree with it completely. Our 1380 has had 10° static advance for the last 18 years and 55,000+ miles and has never had problems with the starter or kick-back of any kind.

Aldon recommended the 10° static with their 'Yellow' distributor that I used until very recently, and they still do. I carried the same static setting over to the Nodiz CPU and it is still perfectly OK.

A standard Midget 1275 has 7° BTDC static, and I'm sure MG would not have designed this in if there was any risk of kick-back above 5°.
Richard



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Re: Timing - Symptoms

Postby bmcecosse » Sat Jul 09, 2016 7:38 pm

Richard - I reckon there's something wrong with your timing marks - I've NEVER been able to get a car to cold start with that level of static advance - nor do I see any need for it. Let the mechanical advance do it's thing once the engine starts.
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Re: Timing - Symptoms

Postby liammonty » Sun Jul 10, 2016 12:29 am

My lightly modified 948 is set to between 10 and 12 degrees static advance with its modified distributor, which has less total mechanical advance (so around 30 degrees max) and it starts as well as a totally standard car.

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Re: Timing - Symptoms

Postby IslipMinor » Sun Jul 10, 2016 8:30 pm

Roy, The standard timing mark has been checked with a dial gauge, as part of the cam timing setup and is correct, and in addition I have fitted a second mark, viewable from above, and that is also spot on using a dial gauge. I can be certain that the timing marks are correct with within 1°, as is the 10° static BTDC.

I would expect that something more like 20° BTDC static would be needed to have an effect on starting.
Richard




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