13 replies to this topic

[cian]

Does anyone have a definitive yes or no to keeping or loosing the tensioner pad if running duplex chain? Starting a build soon

[Ethel]

Probably not, I wouldn't bother with one, and neither did the factory.

[Cooperman]

The problem with the tensioner on a duplex set-up is that instead of the chain loads being put equally into the tensioner pad on each side of the chain, the duplex puts the loads into a single contact area in the centre of the tensioner pad.

On high-revving engines the tensioner pad can break up - I've seen two occasions where this has happened, but on a lower revving engine it is not such an issue, particularly if the chain is changed regularly.

[cian]

So better without then! Cooperman time and again you astonish me with ur knowlegde lol

[Cooperman]

The Mk.1 Cooper 'S' was the first Mini to use a Duplex timing chain and that didn't have a tensioner.

Really it is best to change a duplex chain every 15000 to 20000 miles to preserve the cam timing accuracy.

[cian]

Ive atarted up another thread about different timing gear set ups, i was going to buy the med duplex along with the dsm billet timing cover but with that expense i could possibly go belt drive or other

[Cooperman]

Personally I've never seen the advantage of belt-drive. Once the cam is 'timed-in' accurately and a quality Duplex chain fitted, the cam timing is held to a fairly good tolerance, especially if initial cam timing is 2 degrees advanced from nominal to allow for initial chain stretch. But then, I've had to fix the consequences of cam belt failure in more modern cars on more than one occasion.

[cian]

hmmmm im thinking now revert back to my initial duplex set up I think

[Yoda]

I too would not fit the tensioner and as Cooperman says, i would not go near the belt drive conversion. if it was a benefit, you would hear about more being fitted in my opinion!

[Cooperman]

The lowest cost way to optimise the timing system is to use a good duplex chain with good quality sprockets. Then time the cam in accurately to 2 degs before recommended setting (so for a Kent Cam you would set 106 degs minus 2 degs = 104 degs ATDC) using offset Woodruff Keys as available from Mini Spares.

Unless you are regularly changing the cam, once the correct setting is achieved it will not need re-setting even when a new chain is fitted.

Chain stretch is approximately 1.5 degrees after 1500 miles (that was what I once measured). After that the chain stretch settles down and is within limits until towards the end of life of the chain.

A vernier sprocket set is easier to set, but expensive compared with offset keys.

[cian]

I was gona go vernier gears as i "hopefully" will be timing it myself, i have watched a few videos but could you give me a "dummies" guide to setting the timing cooperman?

[Cooperman]

The way I do it is:

Fit the timing gears with the chain on the dot-to-dot setting after making sure the sprockets will slide easily on the crank & cam by cleaning the sprocket internal diameters with emory.

Set a DTI onto the top of piston no.1 and set TDC very accurately. Fit a crankshaft protractor onto the end of the crank and set a TDC position from protractor to crankcase. You can make a small mark on the crankcase to line TDC against.

Fit a pushrod into no.1 inlet valve hole and set the DTI onto the top of that road. Turn the engine clockwise until the DTI is reading max opening. Back it off until the DTI is reading exactly 0.005" less than max and note the number of degrees, then turn it until it is again reading 0.005" after the TDC position and again note the number of degrees. Halve the difference between these two figures and add that to the first reading. That is the actual cam timing. If it is not within +/- 1 degree use an offset key in the appropriate direction to correct it.

It is best to do each measurement at least 3 times to ensure the readings are correct.

[cian]

Fantastic! This is the simplest way i have heard! Many people seem to speak of it as some sort of dark art!

[Matt1293]

Scrap it