18 replies to this topic

[racingbob]

this new powerspark 65d dizzy just bought

 

at 2500 revs vacuum disconnected shows 18 which i believe a bit low

 

but after a couple seconds it starts to scatter between around 13 and 20

 

doesnt do it at 1500 stays at 14 and 2000 14  all in at 33

 

what you think, may send it back

[tiger99]

I don't know anything about your particular distributor, but if it was a plain Lucas mechanical type that would be a sure sign of shaft or bearing wear, detectable because there is sideways play in the rotor and cam. It gets worse very rapidly, as the bearing bushes generate lots of swarf.

 

I suggest looking for some mechanical sloppiness somewhere.

[carbon]

Worn timing chain?

[racingbob]

Worn timing chain?

doesnt do it on the other dizzy, sent it to AC today

 

only on the new powerspark one at 2500 its the 65d electronic for my mg metro

 

it says made in the UK

[Spider]

It sounds to me like at that speed where you are seeing the scatter (under these circumstances) that the Dissy is on the change over point between the Primary and Secondary Springs, only they are not as well matched as they should be.

[liirge]

It sounds to me like at that speed where you are seeing the scatter (under these circumstances) that the Dissy is on the change over point between the Primary and Secondary Springs, only they are not as well matched as they should be.

Precisely what I was thinking

[racingbob]

went for a good spin this morning about 20 miles

 

i had the new powerspark 65d dizzy in and done a check when got home

 

timed at 33 full advance and got 1000 14, 1500, 14, 2000 14, 2500  18

 

the scatter seemed to have gone. now i know the figures of 2000 revs and 2500 appear low

 

not to sure about 1000 figure but car seemed to go well. be interested to see how 

 

the car compares when i get my old dizzy back which AC is curving

 

All figures were done with VACUUM DISCONTECTED

[ACDodd]

I have the dizzy with me now. Will get to work on it later.

Ac

[ACDodd]

Ok checked it out. Its a long curve sprite unit. It has 32degrees of inbuilt advance, way too long and piston meltingly bad.
I will shorten the curve by 11 to 12 degrees, giving 20 to 21, added with 10 degrees of static advance will give a maximum of 30 to 31.

In terms of curve this dizzy is still adding more advanace past 6000rpm, way too much.

It also delivers too much at 2800 rpm, at 19 degrees at the end of the primary spring.

Much work too do.

Ac

Edited by ACDodd, 26 August 2016 - 07:00 PM.

[racingbob]

makes you wonder how many of our dizzys are correct

and how much were possibly loosing in performance or response

[ACDodd]

That's my point most are wrong, most do not realise how much performance and efficiency they are loosing out on.

Attached Files

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Edited by ACDodd, 26 August 2016 - 07:34 PM.

[ACDodd]

This is the new advance stop ihave had to put in. This reduces the advance by 1/3.

Ok I have re - sprung it. You need to install the dizzy at 10degrees btdc at 900rpm vac disconnected. The curve is all in at 4krpm at 30 to 31 degrees with about 20 at 1900.

Re connect the vacuum after setting.

Ac

Edited by ACDodd, 26 August 2016 - 07:55 PM.

[Spider]

Ok checked it out. Its a long curve sprite unit. It has 32degrees of inbuilt advance, way too long and piston meltingly bad.
I will shorten the curve by 11 to 12 degrees, giving 20 to 21, added with 10 degrees of static advance will give a maximum of 30 to 31.

In terms of curve this dizzy is still adding more advanace past 6000rpm, way too much.

It also delivers too much at 2800 rpm, at 19 degrees at the end of the primary spring.

Much work too do.

Ac

 

     

[petey81]

Ac at his finest 👍👍

[tiger99]

I have no patience for these things any more and would throw it away (even harder throw if it was a Ducellier!} and fit a mappable electronic system such as Megaspark. Time is just too short to be faffing about with stone age technology which is never right. And don't get me going on carburettors!

 

Payback time for properly mapped ignition and fuelling may be shorter than you think, depending on how much fuel is saved. Plus you save time repeatedly every 6 months or so, because it doesn't go out of tune.

 

Except on a valuable old Mini where originality matters, of course.