Worrying Wear On Distributor Drive

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Worrying Wear On Distributor Drive

Post by Mr Bridger » Tue Dec 04, 2018 9:47 pm

Whilst checking the ignition timing on my 5a, I noticed a large amount of backlash in the distributor shaft. I removed the distributor and found the drive gear to be very worn. I'm not sure you will be able to see in the photo but the gear teeth peeks are worn to a sharp point, and some of the peeks are actually jagged. Also, there is a significant step at the bottom of each tooth.

Fortunately I had a used spare distributor which I've fitted. The second photo is of that as a comparison.

I'm aware on some engines you have to set up the distributor drive backlash with shims, but there's nothing in the manual about that on this engine, so any ideas what could have caused the wear? Obviously if left I'd have ended up with oil pump failure so I want to make sure this doesn't happen again.
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Worrying Wear On Distributor Drive

Post by Oldconn » Wed Dec 05, 2018 8:21 am

That would suggest, to me, the engine has been running on the wrong oil. How long have you had it? Also, what's the camshaft like? If that is equally worn it will soon wear out your new distributor shaft.


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Worrying Wear On Distributor Drive

Post by Mr Bridger » Wed Dec 05, 2018 8:39 am

I've driven it about 12k miles since I bought it in June 2016. It's always run on Halfords Classic 20W/50 since I've had it. I had a look at the gear drive on the cam with an endoscope and that looked fine thankfully, but obviously couldn't really see the cam lobes without major dismantling.


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Worrying Wear On Distributor Drive

Post by Coupe Racing » Wed Dec 05, 2018 8:40 am

Is the oil supply sufficient or is a galley blocked


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Worrying Wear On Distributor Drive

Post by Mr Bridger » Wed Dec 05, 2018 8:41 am

I don't know; where is the cam fed from?


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Worrying Wear On Distributor Drive

Post by Coupe Racing » Wed Dec 05, 2018 8:48 am

The Manual shows the oil path from the pump


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Worrying Wear On Distributor Drive

Post by scimjim » Wed Dec 05, 2018 9:09 am

Unless the cam gear is harder than the dizzy gear (which is possible?) it might have been worn prior to being fitted? Can you get some engineers blue and see if the new dizzy is running correctly?


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Worrying Wear On Distributor Drive

Post by Martin Rowe » Wed Dec 05, 2018 9:28 am

I think there will be corrisponding wear on the cam gear, both should be hardned, better have a look down the hole, other thing to check will be the oil pump drive, is that worn in the btm of that dissy, and I take it that the dissy turns free as well, would have taken a bit of load to cause that wear, or mismatched gear pitch. Also all the 'grindings' will be in there somewhere as well.



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Worrying Wear On Distributor Drive

Post by Mr Bridger » Wed Dec 05, 2018 1:34 pm

Thanks for the replies. :)

I had the distributor out about 10k miles ago and looking at the photos with a wiser eye I think there was wear (although not as bad) back then.

From what I could see with my 15 quid endoscope via my mobile phone the gear drive on the cam really does look ok, so I wonder if the cam is made from a harder material than the distributor gear?

The oil drive is ok as I replaced that, again about 10k miles ago, when I fitted an alloy timing wheel.

I like the engineers blue idea, it'll be messy, but may provide further data.

Finally I also wonder about the amount of lubrication the drive is receiving as Coupe Racing suggested, although I'm not sure how to check this.

So lots of theories, I'll have to remove the dissy again tonight and scratch my head further....


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Worrying Wear On Distributor Drive

Post by Roger Pennington » Wed Dec 05, 2018 2:31 pm

While you'd expect both gears to be hardened, I don't think that necessarily guarantees that they are hardened identically, or to the same standard? Once one of them wears through its hardening, then its wear will probably increase rapidly?


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Worrying Wear On Distributor Drive

Post by scimjim » Wed Dec 05, 2018 2:34 pm

And the engine could be on its second or third cam?


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Worrying Wear On Distributor Drive

Post by Mr Bridger » Wed Dec 05, 2018 3:07 pm

That's what I'm wondering Roger.
And yes, according.to the history/reciept file it's a different non standard cam Jim.


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Worrying Wear On Distributor Drive

Post by Old and Slow » Wed Dec 05, 2018 7:04 pm

There was an interesting article on oil in the TVR (I think) Club mag a while back:
I think you need a high zinc content oil, unfortunately Halfords oil doesn't have enough to improve the wear characteristics (800 parts per million). Halfords is rated SE (the API code on the container), so is unsuitable for cars after 1979. The oil is the same as Comma Classic and Castrol XL.
NTDWM but I use Classic Oil (1200 ppm) but Penrite, Millers and Morris are all OK.
the article staes that only oils with an API of SG, SH, SJ or SL should be used.
This website is referenced:
www.api.org/products-and-services/engin ... b_gasoline
I'll see if I can get permission to reproduce the article - it would make interesting reading in Slice.


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Worrying Wear On Distributor Drive

Post by roymck » Wed Dec 05, 2018 7:46 pm

Yes I read that article think it was related to the Rover V8 engines with cam and follower wear in TVR,s



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Worrying Wear On Distributor Drive

Post by Mr Bridger » Wed Dec 05, 2018 8:08 pm

I've read about ZDDP (or the lack of) in modern oils as well, but thought it only affected cam followers. Did you mean that Halfords oil is only suitable for engines after 1979 though Philip? Good thought though,I'll look into it further. Thing is, if it's effecting my engine it'll be effecting other Essex engines :shock:

On a more positive note I took the car out this evening and it is running so much more smoothly. Before it had a hesitation on power take up (the reason I was setting the ignition timing in the first place) but now with the replacement distributor that has gone.

I've managed to take some better photos of the old distributor drive which better show the wear, more for interest than anything else. Ignore the fluff, that was just where I cleaned the oil off!
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