Thread: Electronic Distributor for 202 red

Originally Posted by navigation2000

Hi there,


Try not to misinterpret what a failure of the nylon drive gear signifies.

People often wrongly attribute a failure of this gear to it being made of nylon, or they think it failed because it was old. More often than not, these interpretations would be wrong.

The nylon gear is designed to break if the distributor shaft bearings wear out to the point where they begin binding up.

By doing this(breaking), the nylon gear safeguards the camshaft to distributor drive gear which is cast onto the actual camshaft itself, and is non serviceable.

That's what the nylon gear was designed to protect.

A nylon gear failure almost always signifies that it's time for you to rebuild the distributor, or replace the distributor. It can't be said much plainer than that really.

That said, it does make very good sense to carry the steel gear(with new roll pin) in your toolbox as a backup, as others have suggested.

They're only small and take up hardly any room. One can be quickly installed if the nylon gear ever does fail you.

The steel gear will suffice to get you home, or at least get you to some place where a replacement distributor can be found. Once you get your replacement distributor, just continue to use the nylon gear as per usual.

Running the steel gear at all times is not going to alert you to a dizzy bearing failure, in fact, the steel gear will keep turning a badly worn dizzy to the point where it's completely destroyed, and if that dizzy seizes completely, what's going to happen to the camshaft to distributor drive gear?

Then you'll be looking for a new camshaft as well as a new dizzy....and if you're stuck out in the middle nowhere, or even if this happens in a town, you'll still have more drama than you need.

That's news to me, I've replaced tons of these, never seen a seized dissy in service, but seen plenty of broken nylon gears on otherwise functional dissy's. Hey if it turns you on fit a new nylon gear instead and carry a spare for the day it drops dead (it will). I am always willing to change my mind when you show me a seized-in-service dissy. And I don't mean one that rusted up on a wrecking yard motor.

I got one from a late model 173ci and fitted it into my 186ci...trouble free running. But I still carry the old point dizzy in the tool box....if the fancy once stuffs up I am knackered. Better to drive home with the old girl miss firing than walk home I reckon.

Cheers, Mick

Originally Posted by bee utey

That's news to me, I've replaced tons of these, never seen a seized dissy in service, but seen plenty of broken nylon gears on otherwise functional dissy's. Hey if it turns you on fit a new nylon gear instead and carry a spare for the day it drops dead (it will). I am always willing to change my mind when you show me a seized-in-service dissy. And I don't mean one that rusted up on a wrecking yard motor.

So, by your reasoning, the engineers got it wrong when they decided to install a precautionary nylon link between the dizzy/cam/oil pump on a Holden 6?

That's interesting.

Nope, I haven't had any fully seized Bosch electronic dizzies either, but I've only ever had about half a dozen of them fail on me over the years.

I do know people who claim these dizzies have seized on them fully.

It's been my experience that they tend to stop firing just before they seize.

Once they begin to grind the top bearing to bits, the flying metal fragments become magnetised and attach themselves to either the stator or the reluctor, then when the engine is shut down, one tiny piece of magnetised metal is all it takes to bridge the gap at any point around the perimeter of the stator/reluctor and that's all there is folks, dead short. It will never start again, unless you remove the fragment that's effecting the short.

You can do that several times, and you may actually get it to fire up again briefly, but all that happens is the other bits of metal you couldn't see, or reach, again become magnetised, and start flying around and before you know it, you have another dead short.

That caper grows old pretty quick.

That particular dizzy was as close to seized as I have ever seen, it was no longer turning freely, and felt more like a ratchet in the way it was turning. The shaft was moving up and down at least 1.5 inches, but no, it wasn't quite completely seized.

Not sure if I still have it lying around, I'll have a look tomorrow.

You may have misread my post, I never said to fit a new nylon gear to a dizzy that's already broken one, I said, in that event, fit the steel one to get you home.
Fitting another nylon gear at that point will only get you a short way before it too gets eaten.

Originally Posted by navigation2000

So, by your reasoning, the engineers got it wrong when they decided to install a precautionary nylon link between the dizzy/cam/oil pump on a Holden 6?

That's interesting.

Nope, I haven't had any fully seized Bosch electronic dizzies either, but I've only ever had about half a dozen of them fail on me over the years.

I do know people who claim these dizzies have seized on them fully.

It's been my experience that they tend to stop firing just before they seize.

Once they begin to grind the top bearing to bits, the flying metal fragments become magnetised and attach themselves to either the stator or the reluctor, then when the engine is shut down, one tiny piece of magnetised metal is all it takes to bridge the gap at any point around the perimeter of the stator/reluctor and that's all there is folks, dead short. It will never start again, unless you remove the fragment that's effecting the short.

You can do that several times, and you may actually get it to fire up again briefly, but all that happens is the other bits of metal you couldn't see, or reach, again become magnetised, and start flying around and before you know it, you have another dead short.

That caper grows old pretty quick.

That particular dizzy was as close to seized as I have ever seen, it was no longer turning freely, and felt more like a ratchet in the way it was turning. The shaft was moving up and down at least 1.5 inches, but no, it wasn't quite completely seized.

Not sure if I still have it lying around, I'll have a look tomorrow.

You may have misread my post, I never said to fit a new nylon gear to a dizzy that's already broken one, I said, in that event, fit the steel one to get you home.
Fitting another nylon gear at that point will only get you a short way before it too gets eaten.

I did read all your post. I simply hadn't heard of this theory before. After all, the V8 runs a steel gear off the cam and I've never seen one of them fail. My opinion is that Holden found the nylon gear to save them $5 on each car they produced. After all, it's a simple injection moulding. As for failure of the plastic gear pointing to a failed dissy bearing, I DO know that a white nylon gear immersed in a hot engine environment will perish and fail without any help from a dissy failure. My local emergency road service used to keep nylon gears in their toolboxes, as Holdens would drop dead without warning and this quickie replacement put them back to running without rebuilding dissies. This was just about a daily job back in the glorious 80's.

To put it another way: if your nylon gear failed and you found on inspection your dissy bearings were cactus, you wouldn't just put another gear on and close your ears. All the nylon gears I have replaced after failure in service haven't promptly destroyed cams. And I have been fixing distributors for 25 years or so.

Oh and yes, I have seen a failed bearing, it was a wrecker's yard second hand dirty dissy and it made rude noises enough to scare the owner. A quickie dismantle, a new bush and some oil and off it went, never a problem.

Originally Posted by bee utey

I did read all your post. I simply hadn't heard of this theory before. After all, the V8 runs a steel gear off the cam and I've never seen one of them fail. My opinion is that Holden found the nylon gear to save them $5 on each car they produced. After all, it's a simple injection moulding. As for failure of the plastic gear pointing to a failed dissy bearing, I DO know that a white nylon gear immersed in a hot engine environment will perish and fail without any help from a dissy failure. My local emergency road service used to keep nylon gears in their toolboxes, as Holdens would drop dead without warning and this quickie replacement put them back to running without rebuilding dissies. This was just about a daily job back in the glorious 80's.

To put it another way: if your nylon gear failed and you found on inspection your dissy bearings were cactus, you wouldn't just put another gear on and close your ears. All the nylon gears I have replaced after failure in service haven't promptly destroyed cams. And I have been fixing distributors for 25 years or so.

Oh and yes, I have seen a failed bearing, it was a wrecker's yard second hand dirty dissy and it made rude noises enough to scare the owner. A quickie dismantle, a new bush and some oil and off it went, never a problem.

Ok then, I guess you must be right, "sacrificial distributor gears" mustn't exist.
My apologies.

Originally Posted by navigation2000

Ok then, I guess you must be right, "sacrificial distributor gears" mustn't exist.
My apologies.

Look if it makes you happy I am prepared to believe you are right..

There probably were some cam gear failures as you said. After a redesign of the wicking mechanism to get oil to the top bush in the dissy there were probably faaaar fewer failures. So the nylon gear made it possible for Holdens in 1969 to get through warranty without costing the company heaps. Now with better oils etc field experience suggests dissy seizing is a thing of the distant past, so why put a plastic fuse in an engine? Unless you write yourself a memo: Remember to replace gear/inspect dissy bearing every 50 000km.

Oh, and by the way, Holden engineers recommended strongly to keep the fibre cam gear in the Starfire 4 cylinder. Well, my friend the fusspot did that when he rebuilt his Corona XT130 engine, and the genuine fibre gear failed in 10,000km. So I put in an alloy gear (yes it was noisy) and it lasted another 100 000km before he threw the engine.

Originally Posted by bee utey

Look if it makes you happy I am prepared to believe you are right..

There probably were some cam gear failures as you said. After a redesign of the wicking mechanism to get oil to the top bush in the dissy there were probably faaaar fewer failures. So the nylon gear made it possible for Holdens in 1969 to get through warranty without costing the company heaps. Now with better oils etc field experience suggests dissy seizing is a thing of the distant past, so why put a plastic fuse in an engine? Unless you write yourself a memo: Remember to replace gear/inspect dissy bearing every 50 000km.

Oh, and by the way, Holden engineers recommended strongly to keep the fibre cam gear in the Starfire 4 cylinder. Well, my friend the fusspot did that when he rebuilt his Corona XT130 engine, and the genuine fibre gear failed in 10,000km. So I put in an alloy gear (yes it was noisy) and it lasted another 100 000km before he threw the engine.

Bloke, I'm not sure how or why, but this "sacrificial distributor gear" issue has gone from each of us attempting to offer sound mechanical advice to other punters, to more or less a jousting contest. This certainly wasn't what I intended.

It's not about me trying to up the ante or trump you in any way, and I again apologise if you feel that's what's happening here.

It's simply about keeping recognised mechanical engineering facts/safety procedures in plain view, thus affording anyone looking for these types of advices, the ability to make an informed/correct decision.

Care needs to be taken when offering these kinds of advices publicly, in order to ensure that you're not inadvertently steering someone down the wrong track, for even if your intentions are pure, as I'm sure they are, if something does go awry, you'll likely be blamed.

Engineers aren't wrong all the time, and often they do get it right, but for those times when they can't get it right, they develop safeguards like these rotten little nylon gears, to get around the problems.

Anyone wishing to confirm for themselves the reasoning behind "sacrificial distributor gears" only need to Google "sacrificial distributor gear" and a wealth of links are made available on the subject.

The curious researcher will quickly discover that Holden isn't the only automotive company to use this practice. If the researcher then decides to pursue the subject further, in quick time they'll stumble across multiple cases where these pesky little gears have caused major headaches for other people as well.

I'll add just this link to help:
Distributor Gears- Car Craft Magazine

In fairness, the practice of disposing of the nylon distributor drive gear in favour of the steel oil pump drive gear on a Holden in-line 6, for 24/7 continual use, may very well be advantageous, providing you happen to know the precise metallurgical properties of the camshaft in use, and you know that it's indeed compatible with the steel gear. If that approach is still desirable, just do your homework carefully and make sure for yourself that you're doing the right thing.

For me, the simplest approach is to retain the factory designed part, and keep the steel gear in the toolbox as a backup/spare, to be used in the event of a nylon gear failure.

I don't intend to debate this matter further, and will now duly crawl back under my rock and stay there.



*Footnote: With regard to offering advices over the Internet, if you search for "sacrificial distributor gear" or word links relating to this subject using Google, you'll note that this thread appears high on the hits list, thus meaning that it's now linked to the subject being discussed "forever".

Hence why I urge caution when publicly offering mechanical advices of this kind, for if someone does opt to follow your suggestion that by using the steel gear in the hope that it will last "forever", but then it does just happen to go pear shaped on them, it can lead to the unwanted embarrassment of you being linked with the failure "forever".

This has been educational, thanks navigation2000. Make your own minds up fellas, I know what I will be doing.