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MG Midget and Sprite Technical - Aldon ignitor makes weird noise at high revs!

Hey all,

I have had an Aldon ignitor electronic ignition system for ages and not got round to fitting it, did so yesterday without any major issues, car starts and runs fine but when you give it full throttle a strange clacking noise (similar sound to a bad bearing) happens around the 4000 revs mark. If you increase the revs slowly through the range there is no noise.

As I have had the kit for a while I have lost the fitting instructions but I have fitted it the only way it seems possible.

Has anyone else had a similar issue? any ideas of the cause?

I have checked the rotor arm, magnetic collar that fits over the cam shaft and the electronic pickup to see if there is any sign of contact or damage between them but see no sign of this!

Any help would be greatly appreciated as new noises always seem to mean trouble! I have attached a picture of it in place minus the rotor arm, if anyone sees anything wrong with this pic let me know. By the way this is fitted to a 79 1500 midget.

Thanks again



D Prince

After fitting the Aldon Ignitor (or any similar electronic ignition trigger system) you will need to adjust the ignition timing on your car as these units are able to more precisely deliver a spark than a conventional points system.

I would strongly advise that you get the ignition timing retarded by a few degrees to achieve the correct firing point (i.e. ignition timing) before you run the car or rev the engine. The clacking noise to which you refer to will be the con rod bearings being stressed by a too far advanced ignition. I had to retard the ignition by 3 degrees when I fitted a similar electronic ignition unit to my MGB.

HTH

Mike
Mike

Never had that noise on mine - I've got a spare in a box in the garage with instructions. I'll scan and send if you let me have an address.
John Collinson

As Mike says, you need to adjust your timing when fitting. The gap should be .0025 (assuming the same for 1275/1500), and make sure that the (only) screw is tight. Mine wasn't, and I melted the magnetic collar ! Still works though :o)
Geoff Mears (1970 Midget)

Is this when stationary or when driving?

I agree you should check timing - there's no reason to suppose the little trigger magnets in the collar are aligned with the cam-and-heal mechanism that's used with the points, so you *must* re-time to 7 deg BTDC or whatever mark you use. (And reset for points if you ever revert.)

(Your timing could easily be 45 or is it 90 deg out...)

A
anthony

I think the others are correct, you need to readjust the timing. Sounds like preignition under load. You should have a vacuum retard on the distributor, to with wide open throttle it's probably advancing too far and you don't notice it if the throttle is advanced slowly as the vacuum is higher.
Bill Young

Its more basic then that...the photo tells it all!!!!

1 of 2 things are happening

1st...the vacume advance is set to far closed and cant open up under accelleration, and cauSeing some diruption futher inside the dist......LOOK at the pin in the slot on the right side of the dist.


OR


2nd...you dont have enough length of wire and as the vacume advances its ither streatching out and rubbing agianst the magnetic pick block that goes over the dist shaft...or its hinging and banging into the side of the dist.


Acouple of other notes....

make sure the rotor bug isnt sticking up to high. I had to file mine down a bit...measure with the magnet block and the rotor then without the magnetic block. then file the differance off the rotor bug


where the wires come out of the chip...is a real bad area for (hinging... if that can be a term)and the insulation of the wires will break down and expose the inner metal...caused from the back and forth motion of the vacume advance motion...so try and fix or beef up that area so there is no flexing at that joint... I used a piece of drinking straw and some silicone...and drilled 2 small holes in the dist. cap and ran my wires out that way so there was less arching of those wires....

prop
Prop

I understand that the later Midget distributors were mechanical advance and vacuum retard, so you're not dealing with any vacuum advance here.

Just FYI,

-:G:-
Gryf Ketcherside

Oops... I meant to add that when I switched to a pertronix a while back, I had to adjust the timing. It was out a rather noticeable amount. As was suggested above, the magnetic trigger point won't necessarily be in the same place the points-based trigger point was.

-:G:-
Gryf Ketcherside

hey gryf,

there was only a 2 year period where the mechanical advance came out for the 1275 with a 25D unfortantly I cant remember when that was...I was thinking 73-74..but not sure...I dont think I had to adjust mine...but its pre-emissions control...1971


prop
Prop

Prop et al

UK cars never had vac retard, IIRC.

A
Anthony

Thanks, Ant... I stand corrected! I assumed we both used the same distributor, even if the carbs and other bits were different.

-:G:-
Gryf Ketcherside

This thread was discussed between 30/04/2008 and 01/05/2008

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