14 replies to this topic

[TimS]

does the duplex timing gears have a tensioner like he single chain? iv just built my engine up with the gears and theirs a fair bit of play in the chains and its all brand new

[SCURVY DOG]

NO THEY DONT HAVE A TENSIONER

THERE NEEDS TO BE BIT OF PLAY OTHERWISE THEY WOULD SNAP SAME AS A MOTORBIKE CHAIN

IF YOU ROTATE THE ENGINE IN THE DIRECTION OF TRAVELL YOU SHOULD FIND

THE FRONT PART OF THE CHAIN IS TIGHT THE REAR HAVING THE PLAY

HOPE THIS HELPS

[Dan]

Well, I've always run tensioners on duplex chains without any problems. I haven't heard anyone saying not to before.

[SCURVY DOG]

original duplex timing chains did not run tensioners the back plate and cover are different there is no where to fit a tensioner

[Woody]

The last engine i put together had a tensioner on the duplex (well it had it allready , i just re-built it )

[Dan]

There's only no tensioner on the original duplex 'because the ridiculous rubber band tensioner from the standard original gear didn't fit. No-one really used to care about tensioners back then, a little bit of chain rattle wouldn't be noticed amongst all the other noises in old cars!
I've had tensioners on duplex's for a while now and haven't had a problem, the only timing chain problem I've ever had was the dodgy Kent high velocity multi link type chain which are supposed to be silent but wear out in a couple of months (with or without a tensioner).
The engine front plate and the timing cover are the same for duplex as normal, just with a couple of mods made (countersink the screws that hold the plate to the mains cap at the bottom, relieve the cover where it will hit the chain and remove the spray shield from covers with breathers built in). So I put in the standard A+ spring blade tensioner.

What would be nice would be if someone would make a proper hydraulic tensioner for the chain, I'm sure the Rover V8 one would adapt without too much trouble and there's an oil gallery right behind the damn thing.

[TimS]

i didnt have the counder sunk screws so im going to buy some, for now iv just modified the old ones by filling them down! should i fit the oil thrower back on? and do u recon its ok to just use the old single chain tensioner?

[Madmax]

i bought a new tensioner for mine, only cost about 2 quid, but mine broke in 2 when it came off the old engine so i didnt have a choice

[dklawson]

As Dan said, the original A-Series engines had only the rubber band tensioners on the single-row chain pulleys. The duplex chains didn't have any tensioning. Over here, if you want to add a chain tensioner, the common practice is to get a later A+ front plate and timing cover, modify the plate for the countersunk screws and install as usual. The original A-Series plate and cover simply don't have a place to mount the later spring tensioner.

[Dan]

Yes of course you should put the oil flinger back on, and make sure it's the right way round (well, only if you like keeping oil inside your engine that is).

I have re-used old tensioner blades when changing from single row to duplex if I really had to since the chain runs in a different place so the grooves will be in a different place, but you really should buy a new one. If the tension isn't even across the chain (as it won't be if the chain is running across the old groove) you might cause a chain to fail. They are only a couple of quid and everyone has them in stock I should think.

And get the proper front plate screws mate, when are you likely to open up the timing chest just to replace your 'temporary' fix? Get them from a nut and bolt dealer rather than a Mini place. Just take in the standard ones and ask for a counter sunk version. They should be the same length, remembering that the length is measured differntly on countersunk and normal screws (normal screws measured from under the head, countersunk including the head) so the top of the countersunk screw should meet the bottom of the standard head when you hold the two next to each other if you know what I mean. I didn't explain that very well. Never mind, you'll work it out.

Just make sure they are high tensile and you use the proper size allen key in your torque wrench.

[Boab]

Whats the difference between the single and duplex, apart from the obvious?

[Madmax]

obviously single is a single row chain, duplex is a double row chain,

i believe that the reason for duplex is to eliminate chain stretch which would cause your cam timing to be knocked out over a long time, if you get vernier duplex then you have more of a chance to get the cam timing set up if you install a new cam as you can adjust the degree at which the cam is set to

[Boab]

Cheers

[Dan]

It's also much stronger. Once you start fitting high lift rockers and more powerful valve springs and getting more performance from the engine, the load against the cam followers and therefore the camshaft is increased by quite a lot so you fit a stronger chain.

[TimS]

cheers dan for that! will get ordering 2moz