Duplex Timing Chain - What Do I Require?
Discussion
Hi all,
I am purchasing a Duplex timing chain for my MG engine. What is it that I need to correctly time the cam in.
Firstly which timing chain should I buy?
http://www.minispares.com/Product.aspx?ty=pb&p...
Or Lightened?
http://www.minispares.com/Product.aspx?ty=pb&p...
Do I require any additional parts to fit this? Will my original chain tensioner still work with this?
What offset keys do I require and why?
Thanks all.
Tom
I am purchasing a Duplex timing chain for my MG engine. What is it that I need to correctly time the cam in.
Firstly which timing chain should I buy?
http://www.minispares.com/Product.aspx?ty=pb&p...
Or Lightened?
http://www.minispares.com/Product.aspx?ty=pb&p...
Do I require any additional parts to fit this? Will my original chain tensioner still work with this?
What offset keys do I require and why?
Thanks all.
Tom
To fit a Duplex timing chain you first of all throw away the timing chain tensioner for better reliability and revert to the original Cooper 'S' set-up.
You can either fit the expensive vernier adjustable sprocket of use offset woodruff keys and a non-adjustable timing gear set. Personally I fit the non-adjustable one and use the offset keys to time in the cam accurately. It is surprising how far out the standard cam timing can be.On the engine front plate ate two bolt holes which are under the sprocket. These MUST be countersunk and countersunk 1/4" unf x 5/8" long socket head screws used with Loctite. If you don't the bolt heads will hit the chain!.
Then set up the timing gears to line up the two 'dots' on the sprockets with nos 1 & 4 at TDC. I emory out the sprockets so that they slide easily onto the crankshaft and the camshaft as you're going to be taking then on and off a few times.
This will give you the initial timing. Get a crankshaft protractor and fit it to the end of the crankshaft. set the engine to TDC on 1 & 4 using a DTI and set the protractor to read 0 degrees at a known mark on the gearbox casing (I usually use a blob of paint with a line scratched through it. Re-position the DTI onto the inlet valve pushrod for no.1 and rotate the crankshaft clockwise until you have achieved full opening on No 1 inlet. In fact, read the dial gauge at, say, 0.005" either side of full lift, take the protractor reading at each of these positions. Moid-way between these two angles is the actual inlet timing. For a Kent cam it should be 106 deg and for a BMC/Leyland/Rover it should be 110 deg. If it not to these figures, see whether it is reaching max lift early or late and use the appropriate offset key to correct it. I usually do each measurement 3 times and take the average as it may vary by a degree or so each time due to measuring errors. In fact a 2 degree advance from recommended does allow for chain stretch during use, so that's what I aim for.
Now the cam is timed in you just lock the cam nut with the lock washer, place the thrower disc on the crank end (the dish goes towards the block) and fit the timing cover.
However, some timing covers have a flange inside which clears the simplex chain, but hits the duplex. Just cut/grind this right away to ensure clearance.
Sorry this is a bit of a long post and I hope it's clear. Email me if you need any more.
Good luck - it's a job worth doing,
Peter
You can either fit the expensive vernier adjustable sprocket of use offset woodruff keys and a non-adjustable timing gear set. Personally I fit the non-adjustable one and use the offset keys to time in the cam accurately. It is surprising how far out the standard cam timing can be.On the engine front plate ate two bolt holes which are under the sprocket. These MUST be countersunk and countersunk 1/4" unf x 5/8" long socket head screws used with Loctite. If you don't the bolt heads will hit the chain!.
Then set up the timing gears to line up the two 'dots' on the sprockets with nos 1 & 4 at TDC. I emory out the sprockets so that they slide easily onto the crankshaft and the camshaft as you're going to be taking then on and off a few times.
This will give you the initial timing. Get a crankshaft protractor and fit it to the end of the crankshaft. set the engine to TDC on 1 & 4 using a DTI and set the protractor to read 0 degrees at a known mark on the gearbox casing (I usually use a blob of paint with a line scratched through it. Re-position the DTI onto the inlet valve pushrod for no.1 and rotate the crankshaft clockwise until you have achieved full opening on No 1 inlet. In fact, read the dial gauge at, say, 0.005" either side of full lift, take the protractor reading at each of these positions. Moid-way between these two angles is the actual inlet timing. For a Kent cam it should be 106 deg and for a BMC/Leyland/Rover it should be 110 deg. If it not to these figures, see whether it is reaching max lift early or late and use the appropriate offset key to correct it. I usually do each measurement 3 times and take the average as it may vary by a degree or so each time due to measuring errors. In fact a 2 degree advance from recommended does allow for chain stretch during use, so that's what I aim for.
Now the cam is timed in you just lock the cam nut with the lock washer, place the thrower disc on the crank end (the dish goes towards the block) and fit the timing cover.
However, some timing covers have a flange inside which clears the simplex chain, but hits the duplex. Just cut/grind this right away to ensure clearance.
Sorry this is a bit of a long post and I hope it's clear. Email me if you need any more.
Good luck - it's a job worth doing,
Peter
Cooperman said:
To fit a Duplex timing chain you first of all throw away the timing chain tensioner for better reliability and revert to the original Cooper 'S' set-up.
You can either fit the expensive vernier adjustable sprocket of use offset woodruff keys and a non-adjustable timing gear set. Personally I fit the non-adjustable one and use the offset keys to time in the cam accurately. It is surprising how far out the standard cam timing can be.On the engine front plate ate two bolt holes which are under the sprocket. These MUST be countersunk and countersunk 1/4" unf x 5/8" long socket head screws used with Loctite. If you don't the bolt heads will hit the chain!.
Then set up the timing gears to line up the two 'dots' on the sprockets with nos 1 & 4 at TDC. I emory out the sprockets so that they slide easily onto the crankshaft and the camshaft as you're going to be taking then on and off a few times.
This will give you the initial timing. Get a crankshaft protractor and fit it to the end of the crankshaft. set the engine to TDC on 1 & 4 using a DTI and set the protractor to read 0 degrees at a known mark on the gearbox casing (I usually use a blob of paint with a line scratched through it. Re-position the DTI onto the inlet valve pushrod for no.1 and rotate the crankshaft clockwise until you have achieved full opening on No 1 inlet. In fact, read the dial gauge at, say, 0.005" either side of full lift, take the protractor reading at each of these positions. Moid-way between these two angles is the actual inlet timing. For a Kent cam it should be 106 deg and for a BMC/Leyland/Rover it should be 110 deg. If it not to these figures, see whether it is reaching max lift early or late and use the appropriate offset key to correct it. I usually do each measurement 3 times and take the average as it may vary by a degree or so each time due to measuring errors. In fact a 2 degree advance from recommended does allow for chain stretch during use, so that's what I aim for.
Now the cam is timed in you just lock the cam nut with the lock washer, place the thrower disc on the crank end (the dish goes towards the block) and fit the timing cover.
However, some timing covers have a flange inside which clears the simplex chain, but hits the duplex. Just cut/grind this right away to ensure clearance.
Sorry this is a bit of a long post and I hope it's clear. Email me if you need any more.
Good luck - it's a job worth doing,
Peter
Thanks Peter, I'm sure all will become clear when I look at the engine and timing gear. Thank you for the advice. You can either fit the expensive vernier adjustable sprocket of use offset woodruff keys and a non-adjustable timing gear set. Personally I fit the non-adjustable one and use the offset keys to time in the cam accurately. It is surprising how far out the standard cam timing can be.On the engine front plate ate two bolt holes which are under the sprocket. These MUST be countersunk and countersunk 1/4" unf x 5/8" long socket head screws used with Loctite. If you don't the bolt heads will hit the chain!.
Then set up the timing gears to line up the two 'dots' on the sprockets with nos 1 & 4 at TDC. I emory out the sprockets so that they slide easily onto the crankshaft and the camshaft as you're going to be taking then on and off a few times.
This will give you the initial timing. Get a crankshaft protractor and fit it to the end of the crankshaft. set the engine to TDC on 1 & 4 using a DTI and set the protractor to read 0 degrees at a known mark on the gearbox casing (I usually use a blob of paint with a line scratched through it. Re-position the DTI onto the inlet valve pushrod for no.1 and rotate the crankshaft clockwise until you have achieved full opening on No 1 inlet. In fact, read the dial gauge at, say, 0.005" either side of full lift, take the protractor reading at each of these positions. Moid-way between these two angles is the actual inlet timing. For a Kent cam it should be 106 deg and for a BMC/Leyland/Rover it should be 110 deg. If it not to these figures, see whether it is reaching max lift early or late and use the appropriate offset key to correct it. I usually do each measurement 3 times and take the average as it may vary by a degree or so each time due to measuring errors. In fact a 2 degree advance from recommended does allow for chain stretch during use, so that's what I aim for.
Now the cam is timed in you just lock the cam nut with the lock washer, place the thrower disc on the crank end (the dish goes towards the block) and fit the timing cover.
However, some timing covers have a flange inside which clears the simplex chain, but hits the duplex. Just cut/grind this right away to ensure clearance.
Sorry this is a bit of a long post and I hope it's clear. Email me if you need any more.
Good luck - it's a job worth doing,
Peter
Tom
You're welcome, Tom.
The thing to ensure is that the bolt holes in the front plate are properly countersunk and the chain clears the new countersunk bolt heads and that the timing chain is clear of the chain. Some timing covers just clear whilst others seem to need a bit of 'adjustment' with a hammer. In fact, I have just been doing exactly that. There seem to be about 4 different timing covers. The early ones which don't have the bulge for the tensioner are fine without any modification. Some of the others have an oil thrower flange which must be ground off, others have what may be described as a 'dent' near to where the breather pipe comes out - this needs to be flattened a bit, whilct some seem to go straight on. The reason for deleting the spring tensioner is to improve reliability. I recently stripped an engine which had a duplex chain and a tensioner and the tensioner was on the point of disintegrating. If it had, it would have been most unpleasant.
When you get started, just call me if you have any questions. The timing in using a crankshaft protractor sounds difficult but, if anything, it's the easiest part of the job assuming you have a DTI with a magnetic base.
The thing to ensure is that the bolt holes in the front plate are properly countersunk and the chain clears the new countersunk bolt heads and that the timing chain is clear of the chain. Some timing covers just clear whilst others seem to need a bit of 'adjustment' with a hammer. In fact, I have just been doing exactly that. There seem to be about 4 different timing covers. The early ones which don't have the bulge for the tensioner are fine without any modification. Some of the others have an oil thrower flange which must be ground off, others have what may be described as a 'dent' near to where the breather pipe comes out - this needs to be flattened a bit, whilct some seem to go straight on. The reason for deleting the spring tensioner is to improve reliability. I recently stripped an engine which had a duplex chain and a tensioner and the tensioner was on the point of disintegrating. If it had, it would have been most unpleasant.
When you get started, just call me if you have any questions. The timing in using a crankshaft protractor sounds difficult but, if anything, it's the easiest part of the job assuming you have a DTI with a magnetic base.
Cooperman said:
However, some timing covers have a flange inside which clears the simplex chain, but hits the duplex. Just cut/grind this right away to ensure clearance.
Peter
. i ground away evry thing i could on mine but still i couldnt get the clearence due to the much narrower profile at the one end of the cover. i heated it up and manage to beat it out untill it cleared but it didnt look to pretty but yours may fit ok . if you dont want to go through with the bother of modifying your original timing cover you can get them from most good mini part supplier, if you cant get 1 then let me know i send you one. ..Neale..Peter
dogfather said:
Cooperman said:
However, some timing covers have a flange inside which clears the simplex chain, but hits the duplex. Just cut/grind this right away to ensure clearance.
Peter
. i ground away evry thing i could on mine but still i couldnt get the clearence due to the much narrower profile at the one end of the cover. i heated it up and manage to beat it out untill it cleared but it didnt look to pretty but yours may fit ok . if you dont want to go through with the bother of modifying your original timing cover you can get them from most good mini part supplier, if you cant get 1 then let me know i send you one. ..Neale..Peter
Mr2Mike said:
Cooperman said:
To fit a Duplex timing chain you first of all throw away the timing chain tensioner for better reliability
I never found the A+ tensioners to be particularly unreliable, do you have bad experiences?I've had one tensioner which had broken and was about to disintegrate and another which was in very poor shape. So, I revert to exactly what we had in the original Cooper 'S', which was a 'tensioner-less' chain. I would rather have to change the chain a little more often than risk a tensioner failure on a rally. Thus I build road engines the same for reliability.
Maybe on a simplex chain a tensioner is OK, but on a duplex it's better, IMHO, to go without one,
Peter
Maybe on a simplex chain a tensioner is OK, but on a duplex it's better, IMHO, to go without one,
Peter
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