Hints and Tips - A7 Ignition Timing

Date: Mon, 30 Mar 1998
From: David Laver
To: Jonathan Butler
Subject: A7 Clutch Improvements

Jonathan,

The clutch action can be improved by moving the pivot point. This is done by placing a sliver of bar under the lever in the indentation between the hinge pin and the standard pivot. This gives much more travel at the peddle end and hence a smoother engagement.

On my car I swapped 'sudden death' engagement for a big judder as the plate doesn't realease straight so check everything else if you delve into it. In practice this is only a problem in reverse as it goes from a judder to axle tramp to a rather fast charge at solid objects in less time than ideal. I call it character !

I'm pleased to hear the engine impressed. Don Rawson has an excellent reputation with A7 engines and has had a fair bit of competition success. I've found mine to be very sensitive to ignition timing but not to mixture. Do you know how much advance it has or if the distributer is a fixed advance or automatic ? Does a Speedy have a lever to adjust it on the move ?

David


Date: Tue, 31 Mar 1998
From: David Laver
To: Jonathan Butler
Subject: A7's ignition timing

> The ignition is BTW it seems of fixed timing and as Rawson
> set it. I will see where it is when I remove the dynamo.
> There is no driver control.

Jonathan

I'm pleased to hear swapping from wellies to shoes solved the clutch problem. The Aurelia handles a lot better for moving the seat away from the door into line with the steering wheel and getting some fore-aft adjustment. These things matter a lot - as does familiarity and confidence in the thing.

Ignition timing :

There is no need to remove the dynamo to tell - in fact you'd better find out what it is BEFORE you remove the dynamo so you can reset it!!

What you need to do is to remove the flywheel cover behind the block just ahead of the gear lever. Turn the engine over to find the two 'top dead centre' marks for the pairs of cylinders. Turn it back a good way from a TDC mark and remove the distributor cap. Turn it forwards until the points just open - you can use a slip of paper, a feeler guage, or a circuit tester. Measure how many inches of advance - this is the useful figure. For interest do some basic maths to get degrees of advance.

Now for the shocker - if your engine has been done recently and well maybe not, but the first time I did it it was... Grab the rotor arm and see how far you can rotate it due to poor fit, loose bearings, backlash in the distributor drive gears. With it full one way turn the engine a tad and there is likely to be some more lash from the dynamo drive. Given that the cam shaft is another bit of gear lash away you can see there can be errors with static timing.

Repeat for a sample and give me a spread of values. The best way to tell is to run the engine and use a timing light. This requires you to paint marks on the flywheel in white. I set my timing by running the engine at tickover, rotating the distributor to give the fastest idle speed, then giving it a bit more advance again. Alas I over did it to the point where the block shook off the crank case so I'm keen to know where an expert puts it.

I started last year with a wobbly auto advance distributor and changed to a very good condition fixed advance. Apparently the auto advance is maxed out at 2000rpm so not really an advantage. What I learnt is that it is very sensitive to points gap and timing - and that I have yet to get the knack. I'm also interested in the points gap.

As an asided the really hot 750MC specials drive a modern distributor off the end of the camshaft. This is not to the taste of the VSCC.

David


From: David Cochrane
To: british-cars-pre-war
Date: Mon, 6 Apr 1998
Subject: Re: A7's ignition timing

Just to add my two penn'orth:

I have only timed ignition on magneto or early coil ignition cars with manual advance & retard. I do mainly as David suggests, but have always found that the final setting has to be done on the road. Properly set up, the ignition lever should make a considerable difference to the car's performance in second gear; it should feel very flat when retarded, and show a startling improvement when advanced. When correctly set, in top gear at c.35 mph the lever should be about mid-way; advancing it beyond this will make the engine rumble/very rough. It really is suck it and see.

The above remarks of course apply to cars with manual advance & retard, and 3-speed gearboxes.

Regards,
David.


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