I had previously posted regarding suggestions about what timing I should be trying with my cars setup (see http://www.ausmini.com/forums/viewtopic.php?t=60336&highlight= ) however at the time I was unsure of both the type of Cam and the details of the dizzy.

I've since been able to get onto the mechanic who did the last lot of work on the car and have some new info.

The car is a Cooper S 1275 + 0.060
1.5 roller rockers
1.5in Twin SU's

I have since found out that....

the dizzy is Aldon 100AY
and the Cam is a standard Cooper S cam.

apparently the car had a hotter cam fitter but the previous owner was unhappy about the rough running so the mechanic replaced it back to standard.

I emailed Adlon to get the details on the 100AY and they replied

"The 100AY distributor puts on 24deg @ 5000rpm & static of approximately 6/8 degs.
Giving a total advance of 30/32deg @ 5000rpm."

My question is, ...is this dizzys specs still suitable if I only have a standard cam.

I was also surprised that they say it continues to advance way up to 5000rpm. I though the advance usually is all over by 3000rpm.

I've borrowed an advance timing light, if I was to set timing to 30deg at 3000rpm the dizzy will still add more advance up to 5000rpm.

If I set it at 30deg at 5000rpm there won't be enough advance at 3000rpm.

Am I understanding this correctly or am I missing something?

Cheers

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

I've given up on distributors, but...



how much advance is there at 3000rpm when you've set it to 30deg at 5000?

one of my ignition maps is based on an Aldon 'Yellow', and at full load it has 30deg at 3krpm and 36 at 5krpm - so not *that* much more advance between 3 and 5

by the way, and did you set advance with the vacuum advance disconnected??

Going by this curve graph from Aldon there is a difference of 5 dizzy degrees between 3000 and 5000rpm which is a difference of 10 degrees at the crank.

so 30deg at 3000 would mean 40deg at 5000. That's a bit excessive isn't it?

Dizzy has no vac advance.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

It appears that Aldon haven't really moved with the times. I gave up on the curves in these dissy's. They really only suit leaded fuels. They need a considerably lighter spring in the secondary.

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Springs? I assumed what I have is a electronic distributor. So there are no points and the advance is also handled electronically.

Is that correct?

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

We are talking about an Aldon 100AY? Yeap, it has springs, well all the ones I do have anyway Your not getting mixed up with a 123?

Yours may have had an electronic module fitted to do away with only the points.

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Well it certainly has a electronic module, theres no points, but I didn't realise it still had mechanical weights.

Yeah I know what a 123 is, I just thought this was same but with just the one curve rather than 16.

So if it has weights and springs I guess that also means it could have been modified.

In that case guess I should just check out exactly what it's doing with a timing light.

Last time I checked the timing with a borrowed digital advance timing light it didn't seem to advance as much as that chart suggests.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

At a guess, the guy who did the graph did it on a dissy dyno, which will nearly always give slightly different results to checking it in car with a timing light.

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The graph is from Aldon so I guess it represents how the distributor was set originally.

Still the main thing I am trying to understand is why this dizzy seems to be set up to continue to advance all the way up to 5000rpm when most info I have read discribes dizzys finishing advancing at around 3500rpm.

What I was worried about was that if I set my advance at say 30deg at 3000 and yet the dizzy continues to put more on up to 5000rpm it could be advancing too much.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Yes, it does appear that it would over-advance and by quite a bit !

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Seems to be characteristic of Aldon dizzys. The Aldon Red I have full advance is not in till 5000rpm. Caught me out too until I had the curve read. I had set it at 4000rpm.

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Steve

Ok, so perhaps I should recheck the timing at 5000rpm and make sure it isn't advancing too much.

What would be considered a sensible/safe limit.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Well from a safety point of view, you would want avoid detonation. It would be foolhardy to try and guess where that would occur. I know that MSD do a detector to show detonation and the severity of it, however it has to be calibrated (not hard to do). At those kinda engine revs it is difficult to hear the onset of it and it's not until it get fairly heavy (and damaging) that it can be heard.

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