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Broken Dizzy Belt.....

As I understand it the spark reacts with the atmosphere to produce ozone which has the chemical formula O3 compared with oxygen O2

Ozone is so corrosive that when used commercially (water purification, washing contaminated laundry etc) it has to be produced at site and cannot be transported as there is no vessel material that is suitable.

I know that in laundry applications standard rubber components had to be changed for a different material due to premature failure.

It is the ozone that"corrodes" the belt so when Porsche became aware of this they put a clear plastic breather on the distributor to remove this gas as part of ongoing technical updates.

Now the speculation -

a) Maybe the modification was designed and tested over a relatively short period so with cars over 20 years old the rubber has deteriorated sufficiently to break.

b) Maybe deterioration of other components manifests itself as a larger spark and more ozone.

c) Maybe 20 year rubber is not that great generally.

I bi annually check that both rotor arms are turning and if I was to notice a slight drop in power I would even check these items at the side of the road.

Just disconnect the lead from each coil to distributor in turn and see if the car starts.
 
Thanks

I think you've explained how the rubber belt would snap.

But the bit I don't understand is once the rubber belt has snapped and the second distributor stops spinning. Why would that cause significant damage to the engine at all?

Surely you just end up with one spark instead of two and life goes on?
 
A993LAD said:
But the bit I don't understand is once the rubber belt has snapped and the second distributor stops spinning. Why would that cause significant damage to the engine at all?

Surely you just end up with one spark instead of two and life goes on?
Depends where the rotor arm comes to rest - if it's on a contact, then that plug is going to be doing a lot of sparking...
 
Hi All,

If you download the link I attached above you will see that Hans explains how to replace the belt only, which looks a lot easier than a full strip down like Trev is doing.

However, I have found the following outfit in Germany that offer different types of rebuilds, below is the cheapest.

https://www.fvd.net/de-en/930602015...al-ignition-remanufactured-2-part-repair.html

But isn't Diddi ([email protected] ) offering a rebuild service too?

I also contacted Peter Crago at Ignition car parts ltd ([email protected]) but he came back to me and said that he had trouble getting the belt. As I was only checking out options I never went back to him, but finding the belt and the bearings is not an issue from the research I've done. Perhaps if you supplied the belt and bearings he would offer a price, at least he's UK based.

No affiliation to any of the above.

ATB :)
 
All,

decgraham ask:.........But isn't Diddi ([email protected] ) offering a rebuild service too?

Yes, what do you need parts (kit) or complete revision - just email [email protected]


--> only original parts from BOSCH,CONTI, INA, FAG...........
 
Diddi said:
All,

decgraham ask:.........But isn't Diddi ([email protected] ) offering a rebuild service too?

Yes, what do you need parts (kit) or complete revision - just email [email protected]


original parts from CONTI, INA, FAG...........

Thanks Diddi,

I'm Ok at the moment but will be in touch if I need a rebuild.

ATB :)
 
There was a tale of a 964 owner whose belt broke at considerable knots and he ended up with a bent crank, holed pistons are more common but not as common as nothing, they usually break at start up so don't run with a broken belt. Recommended change is 100k Didi supplies full kit and repair as stated, Type 911 supplies belt, pin and rubber seal kit. Yet another winter project as mine has clocked 170k. Did I once say I was getting bored?
 
Recently gave a mate who has a 964 Anniversary a hand with this job, he bought the bearings from somewhere in Germany, probably the place quoted as they are one off sizes either internal or external bore I can't quite remember.
We replaced all bearings and seals, a bit of a faff but doable if you are okay on the tools, freezing the bearings and heating the housing helped to assemble.
 
Great thread and makes a change to usual valuations....

Ok so I got mine done and re-installed on Friday PM, upshot is that it's a fairly doable job. I managed to remove just the primary shaft and install a new belt over the secondary shaft. Removal of the secondary shaft requires you remove the cap at the bottom which without destroying it seemed difficult and I had no replacement.

My bearings seemed in good order so I simply greased them up which has made my life a little easier.

Unit during install, your can see the two halves separated

1Q807ho.jpg


After install and cleanup

iy7Uvui.jpg


vmxs11f.jpg


The pin is actually tougher than you would imagine and took some serious persuasion to knurl over on both ends to prevent it coming back out, in fact I set-up my 10T bench press to help me out.

guncj9H.jpg


The real key to all of this process is to ensure you align crank pulley and disis to the markings when you remove and when you put back, be extra careful during returning your disis back into the block, they engage with the driven shaft and move, this throws the set-up out of timing, you want the marking to line up exactly and you removed when the dissis are in situ, and not on the way out or in as they move due to the toothed gears.

You can see the rotor arms here aligned with markings on dissi case

udcEo7h.jpg


My belt was in ok order but I did spot a slight fray, I'm glad I've done this job now.

504F31g.jpg


Trev
 
.....ok, good Job !
The second runner should always be removed - that's what often looks like. The cap on the bottom can be removed with a small screwdriver and then brought back to shape. These two bearings often look chaotic !

I have all parts for your dizzy - Infos [email protected]
 

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If you mangle the cap covering the lower bearing in the secondary housing they can be found on ebay, stainless even. Search under core/frost plugs/caps. Not started this yet but got one just in case. 1 1/4" from coreplugsintl.
 

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Thank you for posting guys very informative...............one of the jobs on my overdue "to do" list on the 993
 

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