8 replies to this topic

[malc_west]

Hi, looking to fit a duplex timing chain and gears (was going to get the lighted steel one off mini spares)
Is it a straight forward job? How do I go about keeping the timing correct?
Thanks

[timmy850]

It’s radiator out
Remove crank bolt + timing cover
You may need to remove the engine mount and hold the engine up with a jack
The new timing gears have dots on them to set the timing

[Ethel]

It's not very difficult, but a bit more involved than just swapping the chain & sprockets. You'd have to countersink a couple of screw holes and could still have to fettle the cover to get enough clearance. You could consider an uprated single chain.

 

If you're replacing a worn chain you should consider replacing the sprockets too, which involve setting the cam timing to get the maximum benefit, though just aligning the dots will work.

[panky]

You will need to countersink a couple of the holes that hold the engine end plate on and fit equivalent counter sunk head bolts to clear the duplex gear. Also there may be a dimple in the timing chain cover that will need easing out so the chain doesn't rub.

 

Edited by panky, 28 October 2020 - 02:31 PM.

[malc_west]

What's the wood ruff key think all about then guys

[timmy850]

The woodruff key locks the timing gears in position on the crank and cam. Without them the crank would spin and the gear would stay still

[Ethel]

What's the wood ruff key think all about then guys

 

Like Timmy says, the key sits in slots cut in the shaft & sprocket to fix them together. So you've got 4 slots in separate components - no way can they all be machined consistently enough to all fit together exactly on specification-  especially also allowing for variations in all the teeth & chain links. One way to get the cam as well synchronised with the crank as possible is to use woodruff keys with a step in them that alters the angle of sprocket on the cam by a fixed number of degrees.

 

It's a fairly involved process that's been covered before on the forum & is basically the same for all engines, so you'll find something on Youtube I'm sure.

 

Roughly,

 

Find top dead centre for No1 piston so you can attach a protractor to the crank to measure its rotation from TDC.

 

Find TDC for a specified cam lobe (usually No1 inlet) and read off your protractor what angle the crank's at. Comparing your measured figure with the one specified for the cam tells how many degrees offset you need from the key.

 

 

The factory never bothered that much so you got a minor version of VVT (alters torque according to rpm) - but without the variable bit. 

[Cooperman]

As 'Ethel' has said, there is the potential for what is known as a 'build up of manufacturing tolerances' through the timing mechanism.

With all the original factory parts, it was not unusual for the cam timing to vary from one engine to another by several degrees. Then, with after-market parts, these tolerances can become even greater. The biggest error I have seen when setting using just the 'dot-to-dot' method was 8 degrees retarded. Although the engine will still run, it will never produce really good results and fuel consumption can also suffer.  Of course, you may be lucky and have the timing come up spot-on with standard settings.

Measuring what actually exists and correcting it with an offset woodruff key if necessary means the cam timing is then very accurate.

To do this requires a Dial Test Indicator (DTI) and a crankshaft protractor.

If you are going to do this yourself, I suggest that you search on here as the way to do it has been given in detail. If you can't find it, come back and I'll re-post it for you. It is not particularly difficult, but it must be done correctly and accurately. You can buy offset keys from Mini Spares.

[malc_west]

OK thanks guys, I'd like to try my self. So il do some research and YouTube ect and then I'll have a go and report back with issues I have. Thanks for the input its much appreciated