Replacing Timing Chain

[CaliTrav]

Hi all,

Thought I'd ask the forum for some words of wisdom. My traveller has a rattly timing chain, and being OCD about annoying noises like that I'm half tempted to replace it with the duplex sort. I've read the manual, and that makes it seem relatively straightforward. However, I am conscious of messing up the timing and ending up way out of my depth.

For anyone that's done it, is it as procedural as the book makes it sound? Or is it more difficult than it looks for one reason or another? As I say my main concern is that I cock a doodle diddley up the timing somehow and cause damage - at present it's fine apart from the rattling noise, so the other half of me is tempted to ignore it...

I'm aware that interfering with it would break cardinal rule #3 - if it ain't broke, don't fix it...

(Other rules - #1 Don't weld near the petrol tank, #2 When under the car keep your mouth shut and #4 Try to avoid cars with more than 1 carb )

[pgp001]

I have converted mine to duplex using some Cooper timing chain sprockets that I got from Phil the Hill.

The main thing that needs modifying is the front engine mounting plate, in that there are two fixing screws behind the crank sprocket that will need countersinking to clear the duplex sprocket, I also added a tensioner kit which involves additional holes in the front engine plate.
The countersunk screws can just be seen in this photo.



I did mine while I was rebuilding a spare engine so it was easy to modify the plate before it was fitted, however with the engine in the car that will not be quite so straightforward.

Phil P

[philthehill]

If the timing chain is rattling it is broke.

Fitting the duplex chain set up is easy and should pose no problems for you.
Use the MMOC web site search facility for instructions.
So long as you get the two timing marks in line as per the manual you cannot go wrong.
Any queries just ask on here.

What size engine is fitted?
If a 948cc engine is fitted it will be better if you fit the later timing chain cover with neoprene lip seal. You will also need the flat oil thrower plate.
When countersinking the two 1/4" holes for the countersink screws in the front plate get someone to hold a vacuum cleaner on full power near the hole to suck away the drilling chips. Best if you have a 82 degree countersink but a 90 degree countersink will do. Use Loctite lock and seal to hold the screws in place.

[CaliTrav]

Thanks guys,

It's a 1098 engine. I guess my main concern - and this might be me mistunderstanding how it works - but in pulling the old sprockets off for the duplex set up, don't I lose the timing marks? And with the chain removed, the two shafts aren't linked together and can turn independently - so it would be easy to lose the right setting?

Or can you lock the position so that when you put the new sprockets on, it's already right, bar getting the chain links in the right location?

The nuts and bolts of getting to the chain and removing it I'm fine with (the old adage that it's easier to take things apart!) but my concern as mentioned is that when I'm reassembling it that I interfere with the timing and cause new problems!

[geoberni]

Look up section AA24 and diagram AA16 in the BMC Manual. It's explained there.

[pgp001]

It should be pretty foolproof for you as the two sprockets are both keyed to the shafts.
So as long as the two timing marks on the sprockets are lined up when you slide them onto the shafts complete with your new chain that is all you need to do.

Prior to final assembly, I would test fit each sprocket to its respective shaft making sure it slides on and off without binding, that way if you get it wrong first time it will be easy to slide them back of and and have another go.

Now put each sprocket onto its shaft and line up the timing marks, then pull them off again without rotating anything, when you put them back on with the chain installed they will all be in the correct position

Once you have done it you will wonder why you were so worried about it

Phil P

[geoberni]

Here's the relative pages.... (if the site is accepting images at the moment)

TC1.JPG (191.47 KiB) Viewed 3426 times

TC2.JPG (212.11 KiB) Viewed 3426 times

[Nickol]

Your biggest problem will probably getting the old sprockets and front pulley off. You can buy the three arm extractors quite cheaply these days - often not the best quality tools but for occaisional use ok. Set the Crank to TDC before you start, then all the marks will then be aligned.

[Pete Bags]

As I don't know, I'm going to ask!

What are the benefits of going 'duplex'?

Many thanks,

Pete

[philthehill]

The main benefit is the longevity of timing chains and gears.
The original simplex set up with the twin rubber tensioning rings is a poor design and the rubber rings soon loose their ability to correctly tension the timing chain.
Slack timing chains can lead to erratic cam timing and ignition timing.
The duplex chain can transmit more power and creates less noise. A duplex chain set up is a near must if running a performance camshaft.
You can also fit a tensioner to the duplex chain set up to keep any future slack to the minimum.

You could fit a 'A' Plus simplex set up to the Minor engine which does not have the rubber tensioning rings on the camshaft gear but it does require the tensioner and suitable timing chain cover.
The cheapest and easiest improvement to the timing chain set up is to fit the duplex kit which is near fit and forget.
Use a good quality timing chain for long life.
Some duplex chains are supplied with a joining link. If that is the case the closed end of the link clip must be in the direction of travel.

[Pete Bags]

Many thanks Phil!

[CaliTrav]

Just an update and a couple of follow up questions!

I've now fitted the duplex kit, and you were all right, it isn't as scary as it first seems!

No oil leaks and the noise from the chain is gone so I'm very happy about it. The car is starting easily, idling happily and has no issues in static revving etc.

However on my test run I noticed that it's now a bit more gutless than before on the hills. I'm pretty certain that it isn't sticking valves or a problem with the rockers (all refurbished) but I will double check the clearances anyway. The fuel pump is also only a few months old so unlikely to be a fuelling issue.

That leaves me with timing as the source of the issue. Does this point towards me getting something wrong in fitting the timing kit? I'm thinking probably (hopefully!) not, based on the fact the car is starting and running absolutely fine, barring being low on power. Reading a few of the old threads on this, I keep seeing "advance until it pinks then back it off" as general advice.

My thought was to turn the knurled wheel on the distributor to advance a few clicks on a few test runs, and find a balance between power on the hills and no pinking when accelerating uphill - unless anyone has any other advice or thing I should check?

[kevin s]

Ignoring the possibility you have the valve timing one tooth out the new chain won't be stretched so it will change the ignition timing so yes before doing anything drastic check the ignition timing Ideally I would check it with a timing light first to get it to nominal then advance it a turn at a time on the knurled knob until it starts pinking then back it off a couple of degrees.