Springing; a Surprise

[Myrtles Man]

As part of my efforts to track down and eliminate a slight hesitancy/misfire on Myrtle I removed the distributor to check, clean, replace points and condenser and (lightly) lubricate where appropriate.

Having excavated to mechanical advance/retard level I was interested (though not really surprised; I have some experience of unearthing the work of the master bodger on various cars and bikes I've acquired) to see that the return springs were of different lengths, with the longer of the two making contact with only one of the anchor pins and therefore unable to offer any resistance to the outward movement of the weights which, according to my understanding of the physics of the set-up, is the springs' sole function.

Aha, thinks I, new springs required (may as well get a few hens' teeth at the same time) and phoned round , to no avail. "The Distributor Doctor will have 'em", said one of the unable-to-suppliers and indeed he does. However, in telling him about my requirements, I was reminded that a little knowledge can indeed be a dangerous thing. "They're supposed to be different lengths," said the good doctor, "the longer spring comes into play when the weights reach the end of their outward travel" (why that might be necessary, however, he didn't explain and being unwilling to take up any more of his valuable time on a non-sale, I thanked him for the advice and returned to distributor-reassembly duties).

Is this spring-dissimilarity widely known about (and, indeed, understood) among the dizzy-tinkerers on here? Any clarification will be welcomed and greatly appreciated - everyday's a schoolday as they say.

[philthehill]

He is right in that the springs are of different lengths and strengths and they do need to be for the reasons given.
The springs need to be kept to the same weights as not all weights are the same.
Vizard covers the subject of distributer advance springs and their requirements of use in great detail in his book Tuning BLs A Series engine.

[Myrtles Man]

Thanks for the further clarification Phil. Still can't quite see how the second spring would be needed however as, surely, the outward travel of the weights is ultimately limited by the mechanics of the set-up; ie the weights can only pivot out to the end of their arc no matter how fast the drive shaft is spinning. When I pushed the weights out by hand I saw that the longer spring only came into contact with both pins at the absolute limit of their travel and therefore didn't appear to be contributing anything of use.

[philthehill]

Do not forget that the distributor is made up of several layers which have different roles. Only when the distributor is rotating do some of the parts come into play. A static distributor is a completely different beast to one that is being rotated.

[Myrtles Man]

Fair enough. S'pose it's a bit like computers - don't fully understand how they work but happy to accept that they do.

[Myrtles Man]

Now that I'm at the stage of re-fitting the distributor to the car I've come across another point where I'd appreciate a bit of expert input. I notice that the bottom of the distributor body where the clamping plate sits has a 'moat-like' recessed groove which, I'm guessing, should house a rubber O ring to prevent oil leakage, although none of the exploded diagrams of the distributor that I've seen show such a ring and there wasn't one on the dizzy when I removed it. It does have the O ring in the recess machined into the bush itself though. Should there be an additional sealing ring or not - perhaps someone will be kind enough to clarify.

[philthehill]

If you have the machined groove then there should be a 'O' ring fitted.

Distributer 'O' ring 1 (2).JPG (802.96 KiB) Viewed 1157 times

Distributer 'O' ring 2 (2).JPG (888.77 KiB) Viewed 1157 times

I suspect that this is the 'O' ring you require:-

http://www.somerfordmini.co.uk/eshop/in ... ts_id=4525

There are several distributor 'O' rings fitted so you do need to check the 'O' ring against the distributor. See Somerford Mini parts list for details.

http://www.somerfordmini.co.uk/eshop/in ... page&id=74

[Myrtles Man]

Thanks for your reply Phil. My dizzy does have the O ring that shows in your photos (part way down the bush, set into the machined groove); the thing I'm referring to is the channel (just visible in your first photo) on the underside of the flange round which the clamp fits and which butts (sp?) up against the engine block when the distributor is installed on the engine. It's just that it looks as though it may be intended for housing an O ring that would squeeze up against the block once the clamp is bolted on, but perhaps not.

[philthehill]

There is no 'O' ring fitted in the groove you describe.

The only 'O' rings fitted to the distributor shaft/body are those shown in the photos above.

[Myrtles Man]

Again Phil, thanks for your definitive answer - greatly appreciated.